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Patch series "mm: zap pages with read mmap_sem in munmap for large
mapping", v11.
Background:
Recently, when we ran some vm scalability tests on machines with large memory,
we ran into a couple of mmap_sem scalability issues when unmapping large memory
space, please refer to https://lkml.org/lkml/2017/12/14/733 and
https://lkml.org/lkml/2018/2/20/576.
History:
Then akpm suggested to unmap large mapping section by section and drop mmap_sem
at a time to mitigate it (see https://lkml.org/lkml/2018/3/6/784).
V1 patch series was submitted to the mailing list per Andrew's suggestion
(see https://lkml.org/lkml/2018/3/20/786). Then I received a lot great
feedback and suggestions.
Then this topic was discussed on LSFMM summit 2018. In the summit, Michal
Hocko suggested (also in the v1 patches review) to try "two phases"
approach. Zapping pages with read mmap_sem, then doing via cleanup with
write mmap_sem (for discussion detail, see
https://lwn.net/Articles/753269/)
Approach:
Zapping pages is the most time consuming part, according to the suggestion from
Michal Hocko [1], zapping pages can be done with holding read mmap_sem, like
what MADV_DONTNEED does. Then re-acquire write mmap_sem to cleanup vmas.
But, we can't call MADV_DONTNEED directly, since there are two major drawbacks:
* The unexpected state from PF if it wins the race in the middle of munmap.
It may return zero page, instead of the content or SIGSEGV.
* Can't handle VM_LOCKED | VM_HUGETLB | VM_PFNMAP and uprobe mappings, which
is a showstopper from akpm
But, some part may need write mmap_sem, for example, vma splitting. So,
the design is as follows:
acquire write mmap_sem
lookup vmas (find and split vmas)
deal with special mappings
detach vmas
downgrade_write
zap pages
free page tables
release mmap_sem
The vm events with read mmap_sem may come in during page zapping, but
since vmas have been detached before, they, i.e. page fault, gup, etc,
will not be able to find valid vma, then just return SIGSEGV or -EFAULT as
expected.
If the vma has VM_HUGETLB | VM_PFNMAP, they are considered as special
mappings. They will be handled by falling back to regular do_munmap()
with exclusive mmap_sem held in this patch since they may update vm flags.
But, with the "detach vmas first" approach, the vmas have been detached
when vm flags are updated, so it sounds safe to update vm flags with read
mmap_sem for this specific case. So, VM_HUGETLB and VM_PFNMAP will be
handled by using the optimized path in the following separate patches for
bisectable sake.
Unmapping uprobe areas may need update mm flags (MMF_RECALC_UPROBES).
However it is fine to have false-positive MMF_RECALC_UPROBES according to
uprobes developer. So, uprobe unmap will not be handled by the regular
path.
With the "detach vmas first" approach we don't have to re-acquire mmap_sem
again to clean up vmas to avoid race window which might get the address
space changed since downgrade_write() doesn't release the lock to lead
regression, which simply downgrades to read lock.
And, since the lock acquire/release cost is managed to the minimum and
almost as same as before, the optimization could be extended to any size
of mapping without incurring significant penalty to small mappings.
For the time being, just do this in munmap syscall path. Other
vm_munmap() or do_munmap() call sites (i.e mmap, mremap, etc) remain
intact due to some implementation difficulties since they acquire write
mmap_sem from very beginning and hold it until the end, do_munmap() might
be called in the middle. But, the optimized do_munmap would like to be
called without mmap_sem held so that we can do the optimization. So, if
we want to do the similar optimization for mmap/mremap path, I'm afraid we
would have to redesign them. mremap might be called on very large area
depending on the usecases, the optimization to it will be considered in
the future.
This patch (of 3):
When running some mmap/munmap scalability tests with large memory (i.e.
> 300GB), the below hung task issue may happen occasionally.
INFO: task ps:14018 blocked for more than 120 seconds.
Tainted: G E 4.9.79-009.ali3000.alios7.x86_64 #1
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this
message.
ps D 0 14018 1 0x00000004
ffff885582f84000 ffff885e8682f000 ffff880972943000 ffff885ebf499bc0
ffff8828ee120000 ffffc900349bfca8 ffffffff817154d0 0000000000000040
00ffffff812f872a ffff885ebf499bc0 024000d000948300 ffff880972943000
Call Trace:
[<ffffffff817154d0>] ? __schedule+0x250/0x730
[<ffffffff817159e6>] schedule+0x36/0x80
[<ffffffff81718560>] rwsem_down_read_failed+0xf0/0x150
[<ffffffff81390a28>] call_rwsem_down_read_failed+0x18/0x30
[<ffffffff81717db0>] down_read+0x20/0x40
[<ffffffff812b9439>] proc_pid_cmdline_read+0xd9/0x4e0
[<ffffffff81253c95>] ? do_filp_open+0xa5/0x100
[<ffffffff81241d87>] __vfs_read+0x37/0x150
[<ffffffff812f824b>] ? security_file_permission+0x9b/0xc0
[<ffffffff81242266>] vfs_read+0x96/0x130
[<ffffffff812437b5>] SyS_read+0x55/0xc0
[<ffffffff8171a6da>] entry_SYSCALL_64_fastpath+0x1a/0xc5
It is because munmap holds mmap_sem exclusively from very beginning to all
the way down to the end, and doesn't release it in the middle. When
unmapping large mapping, it may take long time (take ~18 seconds to unmap
320GB mapping with every single page mapped on an idle machine).
Zapping pages is the most time consuming part, according to the suggestion
from Michal Hocko [1], zapping pages can be done with holding read
mmap_sem, like what MADV_DONTNEED does. Then re-acquire write mmap_sem to
cleanup vmas.
But, some part may need write mmap_sem, for example, vma splitting. So,
the design is as follows:
acquire write mmap_sem
lookup vmas (find and split vmas)
deal with special mappings
detach vmas
downgrade_write
zap pages
free page tables
release mmap_sem
The vm events with read mmap_sem may come in during page zapping, but
since vmas have been detached before, they, i.e. page fault, gup, etc,
will not be able to find valid vma, then just return SIGSEGV or -EFAULT as
expected.
If the vma has VM_HUGETLB | VM_PFNMAP, they are considered as special
mappings. They will be handled by without downgrading mmap_sem in this
patch since they may update vm flags.
But, with the "detach vmas first" approach, the vmas have been detached
when vm flags are updated, so it sounds safe to update vm flags with read
mmap_sem for this specific case. So, VM_HUGETLB and VM_PFNMAP will be
handled by using the optimized path in the following separate patches for
bisectable sake.
Unmapping uprobe areas may need update mm flags (MMF_RECALC_UPROBES).
However it is fine to have false-positive MMF_RECALC_UPROBES according to
uprobes developer.
With the "detach vmas first" approach we don't have to re-acquire mmap_sem
again to clean up vmas to avoid race window which might get the address
space changed since downgrade_write() doesn't release the lock to lead
regression, which simply downgrades to read lock.
And, since the lock acquire/release cost is managed to the minimum and
almost as same as before, the optimization could be extended to any size
of mapping without incurring significant penalty to small mappings.
For the time being, just do this in munmap syscall path. Other
vm_munmap() or do_munmap() call sites (i.e mmap, mremap, etc) remain
intact due to some implementation difficulties since they acquire write
mmap_sem from very beginning and hold it until the end, do_munmap() might
be called in the middle. But, the optimized do_munmap would like to be
called without mmap_sem held so that we can do the optimization. So, if
we want to do the similar optimization for mmap/mremap path, I'm afraid we
would have to redesign them. mremap might be called on very large area
depending on the usecases, the optimization to it will be considered in
the future.
With the patches, exclusive mmap_sem hold time when munmap a 80GB address
space on a machine with 32 cores of E5-2680 @ 2.70GHz dropped to us level
from second.
munmap_test-15002 [008] 594.380138: funcgraph_entry: |
__vm_munmap() {
munmap_test-15002 [008] 594.380146: funcgraph_entry: !2485684 us
| unmap_region();
munmap_test-15002 [008] 596.865836: funcgraph_exit: !2485692 us
| }
Here the execution time of unmap_region() is used to evaluate the time of
holding read mmap_sem, then the remaining time is used with holding
exclusive lock.
[1] https://lwn.net/Articles/753269/
Link: http://lkml.kernel.org/r/1537376621-51150-2-git-send-email-yang.shi@linux.alibaba.com
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>Suggested-by: Michal Hocko <mhocko@kernel.org>
Suggested-by: Kirill A. Shutemov <kirill@shutemov.name>
Suggested-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Matthew Wilcox <willy@infradead.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Add might_sleep() call to vfree() to catch potential sleep-in-atomic bugs
earlier.
[aryabinin@virtuozzo.com: drop might_sleep_if() from kvfree()]
Link: http://lkml.kernel.org/r/7e19e4df-b1a6-29bd-9ae7-0266d50bef1d@virtuozzo.com
Link: http://lkml.kernel.org/r/20180914130512.10394-3-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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vfree() might sleep if called not in interrupt context. Explain that in
the comment.
Link: http://lkml.kernel.org/r/20180914130512.10394-2-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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vfree() might sleep if called not in interrupt context. So does kvfree()
too. Fix misleading kvfree()'s comment about allowed context.
Link: http://lkml.kernel.org/r/20180914130512.10394-1-aryabinin@virtuozzo.com
Fixes: 04b8e946075d ("mm/util.c: improve kvfree() kerneldoc")
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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match_string() returns the index of an array for a matching string, which
can be used intead of open coded implementation.
Link: http://lkml.kernel.org/r/1536988365-50310-1-git-send-email-zhongjiang@huawei.com
Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Remove duplicated include linux/memremap.h
Link: http://lkml.kernel.org/r/20180917131308.16420-1-yuehaibing@huawei.com
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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should_suppress_show_mem() was introduced to reduce the overhead of
show_mem on large NUMA systems. Things have changed since then though.
Namely c78e93630d15 ("mm: do not walk all of system memory during
show_mem") has reduced the overhead considerably.
Moreover warn_alloc_show_mem clears SHOW_MEM_FILTER_NODES when called from
the IRQ context already so we are not printing per node stats.
Remove should_suppress_show_mem because we are losing potentially
interesting information about allocation failures. We have seen a bug
report where system gets unresponsive under memory pressure and there is
only
kernel: [2032243.696888] qlge 0000:8b:00.1 ql1: Could not get a page chunk, i=8, clean_idx =200 .
kernel: [2032243.710725] swapper/7: page allocation failure: order:1, mode:0x1084120(GFP_ATOMIC|__GFP_COLD|__GFP_COMP)
without an additional information for debugging. It would be great to see
the state of the page allocator at the moment.
Link: http://lkml.kernel.org/r/20180907114334.7088-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The refault stats go better with the page fault stats, and are of
higher interest than the stats on LRU operations. In fact they used to
be grouped together; when the LRU operation stats were added later on,
they were wedged in between.
Move them back together. Documentation/admin-guide/cgroup-v2.rst
already lists them in the right order.
Link: http://lkml.kernel.org/r/20181010140239.GA2527@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The page cache and most shrinkable slab caches hold data that has been
read from disk, but there are some caches that only cache CPU work, such
as the dentry and inode caches of procfs and sysfs, as well as the subset
of radix tree nodes that track non-resident page cache.
Currently, all these are shrunk at the same rate: using DEFAULT_SEEKS for
the shrinker's seeks setting tells the reclaim algorithm that for every
two page cache pages scanned it should scan one slab object.
This is a bogus setting. A virtual inode that required no IO to create is
not twice as valuable as a page cache page; shadow cache entries with
eviction distances beyond the size of memory aren't either.
In most cases, the behavior in practice is still fine. Such virtual
caches don't tend to grow and assert themselves aggressively, and usually
get picked up before they cause problems. But there are scenarios where
that's not true.
Our database workloads suffer from two of those. For one, their file
workingset is several times bigger than available memory, which has the
kernel aggressively create shadow page cache entries for the non-resident
parts of it. The workingset code does tell the VM that most of these are
expendable, but the VM ends up balancing them 2:1 to cache pages as per
the seeks setting. This is a huge waste of memory.
These workloads also deal with tens of thousands of open files and use
/proc for introspection, which ends up growing the proc_inode_cache to
absurdly large sizes - again at the cost of valuable cache space, which
isn't a reasonable trade-off, given that proc inodes can be re-created
without involving the disk.
This patch implements a "zero-seek" setting for shrinkers that results in
a target ratio of 0:1 between their objects and IO-backed caches. This
allows such virtual caches to grow when memory is available (they do
cache/avoid CPU work after all), but effectively disables them as soon as
IO-backed objects are under pressure.
It then switches the shrinkers for procfs and sysfs metadata, as well as
excess page cache shadow nodes, to the new zero-seek setting.
Link: http://lkml.kernel.org/r/20181009184732.762-5-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Domas Mituzas <dmituzas@fb.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Rik van Riel <riel@surriel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Make it easier to catch bugs in the shadow node shrinker by adding a
counter for the shadow nodes in circulation.
[akpm@linux-foundation.org: assert that irqs are disabled, for __inc_lruvec_page_state()]
[akpm@linux-foundation.org: s/WARN_ON_ONCE/VM_WARN_ON_ONCE/, per Johannes]
Link: http://lkml.kernel.org/r/20181009184732.762-4-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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No need to use the preemption-safe lruvec state function inside the
reclaim region that has irqs disabled.
Link: http://lkml.kernel.org/r/20181009184732.762-3-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Rik van Riel <riel@surriel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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When systems are overcommitted and resources become contended, it's hard
to tell exactly the impact this has on workload productivity, or how close
the system is to lockups and OOM kills. In particular, when machines work
multiple jobs concurrently, the impact of overcommit in terms of latency
and throughput on the individual job can be enormous.
In order to maximize hardware utilization without sacrificing individual
job health or risk complete machine lockups, this patch implements a way
to quantify resource pressure in the system.
A kernel built with CONFIG_PSI=y creates files in /proc/pressure/ that
expose the percentage of time the system is stalled on CPU, memory, or IO,
respectively. Stall states are aggregate versions of the per-task delay
accounting delays:
cpu: some tasks are runnable but not executing on a CPU
memory: tasks are reclaiming, or waiting for swapin or thrashing cache
io: tasks are waiting for io completions
These percentages of walltime can be thought of as pressure percentages,
and they give a general sense of system health and productivity loss
incurred by resource overcommit. They can also indicate when the system
is approaching lockup scenarios and OOMs.
To do this, psi keeps track of the task states associated with each CPU
and samples the time they spend in stall states. Every 2 seconds, the
samples are averaged across CPUs - weighted by the CPUs' non-idle time to
eliminate artifacts from unused CPUs - and translated into percentages of
walltime. A running average of those percentages is maintained over 10s,
1m, and 5m periods (similar to the loadaverage).
[hannes@cmpxchg.org: doc fixlet, per Randy]
Link: http://lkml.kernel.org/r/20180828205625.GA14030@cmpxchg.org
[hannes@cmpxchg.org: code optimization]
Link: http://lkml.kernel.org/r/20180907175015.GA8479@cmpxchg.org
[hannes@cmpxchg.org: rename psi_clock() to psi_update_work(), per Peter]
Link: http://lkml.kernel.org/r/20180907145404.GB11088@cmpxchg.org
[hannes@cmpxchg.org: fix build]
Link: http://lkml.kernel.org/r/20180913014222.GA2370@cmpxchg.org
Link: http://lkml.kernel.org/r/20180828172258.3185-9-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Daniel Drake <drake@endlessm.com>
Tested-by: Suren Baghdasaryan <surenb@google.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <jweiner@fb.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Enderborg <peter.enderborg@sony.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Delay accounting already measures the time a task spends in direct reclaim
and waiting for swapin, but in low memory situations tasks spend can spend
a significant amount of their time waiting on thrashing page cache. This
isn't tracked right now.
To know the full impact of memory contention on an individual task,
measure the delay when waiting for a recently evicted active cache page to
read back into memory.
Also update tools/accounting/getdelays.c:
[hannes@computer accounting]$ sudo ./getdelays -d -p 1
print delayacct stats ON
PID 1
CPU count real total virtual total delay total delay average
50318 745000000 847346785 400533713 0.008ms
IO count delay total delay average
435 122601218 0ms
SWAP count delay total delay average
0 0 0ms
RECLAIM count delay total delay average
0 0 0ms
THRASHING count delay total delay average
19 12621439 0ms
Link: http://lkml.kernel.org/r/20180828172258.3185-4-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Daniel Drake <drake@endlessm.com>
Tested-by: Suren Baghdasaryan <surenb@google.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <jweiner@fb.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Enderborg <peter.enderborg@sony.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Refaults happen during transitions between workingsets as well as in-place
thrashing. Knowing the difference between the two has a range of
applications, including measuring the impact of memory shortage on the
system performance, as well as the ability to smarter balance pressure
between the filesystem cache and the swap-backed workingset.
During workingset transitions, inactive cache refaults and pushes out
established active cache. When that active cache isn't stale, however,
and also ends up refaulting, that's bonafide thrashing.
Introduce a new page flag that tells on eviction whether the page has been
active or not in its lifetime. This bit is then stored in the shadow
entry, to classify refaults as transitioning or thrashing.
How many page->flags does this leave us with on 32-bit?
20 bits are always page flags
21 if you have an MMU
23 with the zone bits for DMA, Normal, HighMem, Movable
29 with the sparsemem section bits
30 if PAE is enabled
31 with this patch.
So on 32-bit PAE, that leaves 1 bit for distinguishing two NUMA nodes. If
that's not enough, the system can switch to discontigmem and re-gain the 6
or 7 sparsemem section bits.
Link: http://lkml.kernel.org/r/20180828172258.3185-3-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Daniel Drake <drake@endlessm.com>
Tested-by: Suren Baghdasaryan <surenb@google.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <jweiner@fb.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Enderborg <peter.enderborg@sony.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Patch series "psi: pressure stall information for CPU, memory, and IO", v4.
Overview
PSI reports the overall wallclock time in which the tasks in a system (or
cgroup) wait for (contended) hardware resources.
This helps users understand the resource pressure their workloads are
under, which allows them to rootcause and fix throughput and latency
problems caused by overcommitting, underprovisioning, suboptimal job
placement in a grid; as well as anticipate major disruptions like OOM.
Real-world applications
We're using the data collected by PSI (and its previous incarnation,
memdelay) quite extensively at Facebook, and with several success stories.
One usecase is avoiding OOM hangs/livelocks. The reason these happen is
because the OOM killer is triggered by reclaim not being able to free
pages, but with fast flash devices there is *always* some clean and
uptodate cache to reclaim; the OOM killer never kicks in, even as tasks
spend 90% of the time thrashing the cache pages of their own executables.
There is no situation where this ever makes sense in practice. We wrote a
<100 line POC python script to monitor memory pressure and kill stuff way
before such pathological thrashing leads to full system losses that would
require forcible hard resets.
We've since extended and deployed this code into other places to guarantee
latency and throughput SLAs, since they're usually violated way before the
kernel OOM killer would ever kick in.
It is available here: https://github.com/facebookincubator/oomd
Eventually we probably want to trigger the in-kernel OOM killer based on
extreme sustained pressure as well, so that Linux can avoid memory
livelocks - which technically aren't deadlocks, but to the user
indistinguishable from them - out of the box. We'd continue using OOMD as
the first line of defense to ensure workload health and implement complex
kill policies that are beyond the scope of the kernel.
We also use PSI memory pressure for loadshedding. Our batch job
infrastructure used to use heuristics based on various VM stats to
anticipate OOM situations, with lackluster success. We switched it to PSI
and managed to anticipate and avoid OOM kills and lockups fairly reliably.
The reduction of OOM outages in the worker pool raised the pool's
aggregate productivity, and we were able to switch that service to smaller
machines.
Lastly, we use cgroups to isolate a machine's main workload from
maintenance crap like package upgrades, logging, configuration, as well as
to prevent multiple workloads on a machine from stepping on each others'
toes. We were not able to configure this properly without the pressure
metrics; we would see latency or bandwidth drops, but it would often be
hard to impossible to rootcause it post-mortem.
We now log and graph pressure for the containers in our fleet and can
trivially link latency spikes and throughput drops to shortages of
specific resources after the fact, and fix the job config/scheduling.
PSI has also received testing, feedback, and feature requests from Android
and EndlessOS for the purpose of low-latency OOM killing, to intervene in
pressure situations before the UI starts hanging.
How do you use this feature?
A kernel with CONFIG_PSI=y will create a /proc/pressure directory with 3
files: cpu, memory, and io. If using cgroup2, cgroups will also have
cpu.pressure, memory.pressure and io.pressure files, which simply
aggregate task stalls at the cgroup level instead of system-wide.
The cpu file contains one line:
some avg10=2.04 avg60=0.75 avg300=0.40 total=157656722
The averages give the percentage of walltime in which one or more tasks
are delayed on the runqueue while another task has the CPU. They're
recent averages over 10s, 1m, 5m windows, so you can tell short term
trends from long term ones, similarly to the load average.
The total= value gives the absolute stall time in microseconds. This
allows detecting latency spikes that might be too short to sway the
running averages. It also allows custom time averaging in case the
10s/1m/5m windows aren't adequate for the usecase (or are too coarse with
future hardware).
What to make of this "some" metric? If CPU utilization is at 100% and CPU
pressure is 0, it means the system is perfectly utilized, with one
runnable thread per CPU and nobody waiting. At two or more runnable tasks
per CPU, the system is 100% overcommitted and the pressure average will
indicate as much. From a utilization perspective this is a great state of
course: no CPU cycles are being wasted, even when 50% of the threads were
to go idle (as most workloads do vary). From the perspective of the
individual job it's not great, however, and they would do better with more
resources. Depending on what your priority and options are, raised "some"
numbers may or may not require action.
The memory file contains two lines:
some avg10=70.24 avg60=68.52 avg300=69.91 total=3559632828
full avg10=57.59 avg60=58.06 avg300=60.38 total=3300487258
The some line is the same as for cpu, the time in which at least one task
is stalled on the resource. In the case of memory, this includes waiting
on swap-in, page cache refaults and page reclaim.
The full line, however, indicates time in which *nobody* is using the CPU
productively due to pressure: all non-idle tasks are waiting for memory in
one form or another. Significant time spent in there is a good trigger
for killing things, moving jobs to other machines, or dropping incoming
requests, since neither the jobs nor the machine overall are making too
much headway.
The io file is similar to memory. Because the block layer doesn't have a
concept of hardware contention right now (how much longer is my IO request
taking due to other tasks?), it reports CPU potential lost on all IO
delays, not just the potential lost due to competition.
FAQ
Q: How is PSI's CPU component different from the load average?
A: There are several quirks in the load average that make it hard to
impossible to tell how overcommitted the CPU really is.
1. The load average is reported as a raw number of active tasks.
You need to know how many CPUs there are in the system, how many
CPUs the workload is allowed to use, then think about what the
proportion between load and the number of CPUs mean for the
tasks trying to run.
PSI reports the percentage of wallclock time in which tasks are
waiting for a CPU to run on. It doesn't matter how many CPUs are
present or usable. The number always tells the quality of life
of tasks in the system or in a particular cgroup.
2. The shortest averaging window is 1m, which is extremely coarse,
and it's sampled in 5s intervals. A *lot* can happen on a CPU in
5 seconds. This *may* be able to identify persistent long-term
trends and very clear and obvious overloads, but it's unusable
for latency spikes and more subtle overutilization.
PSI's shortest window is 10s. It also exports the cumulative
stall times (in microseconds) of synchronously recorded events.
3. On Linux, the load average for historical reasons includes all
TASK_UNINTERRUPTIBLE tasks. This gives a broader sense of how
busy the system is, but on the flipside it doesn't distinguish
whether tasks are likely to contend over the CPU or IO - which
obviously requires very different interventions from a sys admin
or a job scheduler.
PSI reports independent metrics for CPU and IO. You can tell
which resource is making the tasks wait, but in conjunction
still see how overloaded the system is overall.
Q: What's the cost / performance impact of this feature?
A: PSI's primary cost is in the scheduler, in particular task wakeups
and sleeps.
I benchmarked this code using Facebook's two most scheduling
sensitive workloads: memcache and webserver. They handle a ton of
small requests - lots of wakeups and sleeps with little actual work
in between - so they tend to be canaries for scheduler regressions.
In the tests, the boxes were handling live traffic over the course
of several hours. Half the machines, the control, ran with
CONFIG_PSI=n.
For memcache I used eight machines total. They're 2-socket, 14
core, 56 thread boxes. The test runs for half the test period,
flips the test and control kernels on the hardware to rule out HW
factors, DC location etc., then runs the other half of the test.
For the webservers, I used 32 machines total. They're single
socket, 16 core, 32 thread machines.
During the memcache test, CPU load was nopsi=78.05% psi=78.98% in
the first half and nopsi=77.52% psi=78.25%, so PSI added between
0.7 and 0.9 percentage points to the CPU load, a difference of
about 1%.
UPDATE: I re-ran this test with the v3 version of this patch set
and the CPU utilization was equivalent between test and control.
UPDATE: v4 is on par with v3.
As far as end-to-end request latency from the client perspective
goes, we don't sample those finely enough to capture the requests
going to those particular machines during the test, but we know the
p50 turnaround time in this workload is 54us, and perf bench sched
pipe on those machines show nopsi=5.232666 us/op and psi=5.587347
us/op, so this doesn't add much here either.
The profile for the pipe benchmark shows:
0.87% sched-pipe [kernel.vmlinux] [k] psi_group_change
0.83% perf.real [kernel.vmlinux] [k] psi_group_change
0.82% perf.real [kernel.vmlinux] [k] psi_task_change
0.58% sched-pipe [kernel.vmlinux] [k] psi_task_change
The webserver load is running inside 4 nested cgroup levels. The
CPU load with both nopsi and psi kernels was indistinguishable at
81%.
For comparison, we had to disable the cgroup cpu controller on the
webservers because it added 4 percentage points to the CPU% during
this same exact test.
Versions of this accounting code now run on 80% of our fleet. None
of our workloads have reported regressions during the rollout.
Daniel Drake said:
: I just retested the latest version at
: http://git.cmpxchg.org/cgit.cgi/linux-psi.git (Linux 4.18) and the results
: are great.
:
: Test setup:
: Endless OS
: GeminiLake N4200 low end laptop
: 2GB RAM
: swap (and zram swap) disabled
:
: Baseline test: open a handful of large-ish apps and several website
: tabs in Google Chrome.
:
: Results: after a couple of minutes, system is excessively thrashing, mouse
: cursor can barely be moved, UI is not responding to mouse clicks, so it's
: impractical to recover from this situation as an ordinary user
:
: Add my simple killer:
: https://gist.github.com/dsd/a8988bf0b81a6163475988120fe8d9cd
:
: Results: when the thrashing causes the UI to become sluggish, the killer
: steps in and kills something (usually a chrome tab), and the system
: remains usable. I repeatedly opened more apps and more websites over a 15
: minute period but I wasn't able to get the system to a point of UI
: unresponsiveness.
Suren said:
: Backported to 4.9 and retested on ARMv8 8 code system running Android.
: Signals behave as expected reacting to memory pressure, no jumps in
: "total" counters that would indicate an overflow/underflow issues. Nicely
: done!
This patch (of 9):
If we keep just enough refault information to match the *current* page
cache during reclaim time, we could lose a lot of events when there is
only a temporary spike in non-cache memory consumption that pushes out all
the cache. Once cache comes back, we won't see those refaults. They
might not be actionable for LRU aging, but we want to know about them for
measuring memory pressure.
[hannes@cmpxchg.org: switch to NUMA-aware lru and slab counters]
Link: http://lkml.kernel.org/r/20181009184732.762-2-hannes@cmpxchg.org
Link: http://lkml.kernel.org/r/20180828172258.3185-2-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <jweiner@fb.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Rik van Riel <riel@surriel.com>
Tested-by: Daniel Drake <drake@endlessm.com>
Tested-by: Suren Baghdasaryan <surenb@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Cc: Christopher Lameter <cl@linux.com>
Cc: Peter Enderborg <peter.enderborg@sony.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Kmalloc cache names can get quite long for large object sizes, when the
sizes are expressed in bytes. Use 'k' and 'M' prefixes to make the names
as short as possible e.g. in /proc/slabinfo. This works, as we mostly
use power-of-two sizes, with exceptions only below 1k.
Example: 'kmalloc-4194304' becomes 'kmalloc-4M'
Link: http://lkml.kernel.org/r/20180731090649.16028-7-vbabka@suse.cz
Suggested-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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The vmstat counter NR_INDIRECTLY_RECLAIMABLE_BYTES was introduced by
commit eb59254608bc ("mm: introduce NR_INDIRECTLY_RECLAIMABLE_BYTES") with
the goal of accounting objects that can be reclaimed, but cannot be
allocated via a SLAB_RECLAIM_ACCOUNT cache. This is now possible via
kmalloc() with __GFP_RECLAIMABLE flag, and the dcache external names user
is converted.
The counter is however still useful for accounting direct page allocations
(i.e. not slab) with a shrinker, such as the ION page pool. So keep it,
and:
- change granularity to pages to be more like other counters; sub-page
allocations should be able to use kmalloc
- rename the counter to NR_KERNEL_MISC_RECLAIMABLE
- expose the counter again in vmstat as "nr_kernel_misc_reclaimable"; we can
again remove the check for not printing "hidden" counters
Link: http://lkml.kernel.org/r/20180731090649.16028-5-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Kmem caches can be created with a SLAB_RECLAIM_ACCOUNT flag, which
indicates they contain objects which can be reclaimed under memory
pressure (typically through a shrinker). This makes the slab pages
accounted as NR_SLAB_RECLAIMABLE in vmstat, which is reflected also the
MemAvailable meminfo counter and in overcommit decisions. The slab pages
are also allocated with __GFP_RECLAIMABLE, which is good for
anti-fragmentation through grouping pages by mobility.
The generic kmalloc-X caches are created without this flag, but sometimes
are used also for objects that can be reclaimed, which due to varying size
cannot have a dedicated kmem cache with SLAB_RECLAIM_ACCOUNT flag. A
prominent example are dcache external names, which prompted the creation
of a new, manually managed vmstat counter NR_INDIRECTLY_RECLAIMABLE_BYTES
in commit f1782c9bc547 ("dcache: account external names as indirectly
reclaimable memory").
To better handle this and any other similar cases, this patch introduces
SLAB_RECLAIM_ACCOUNT variants of kmalloc caches, named kmalloc-rcl-X.
They are used whenever the kmalloc() call passes __GFP_RECLAIMABLE among
gfp flags. They are added to the kmalloc_caches array as a new type.
Allocations with both __GFP_DMA and __GFP_RECLAIMABLE will use a dma type
cache.
This change only applies to SLAB and SLUB, not SLOB. This is fine, since
SLOB's target are tiny system and this patch does add some overhead of
kmem management objects.
Link: http://lkml.kernel.org/r/20180731090649.16028-3-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Patch series "kmalloc-reclaimable caches", v4.
As discussed at LSF/MM [1] here's a patchset that introduces
kmalloc-reclaimable caches (more details in the second patch) and uses
them for dcache external names. That allows us to repurpose the
NR_INDIRECTLY_RECLAIMABLE_BYTES counter later in the series.
With patch 3/6, dcache external names are allocated from kmalloc-rcl-*
caches, eliminating the need for manual accounting. More importantly, it
also ensures the reclaimable kmalloc allocations are grouped in pages
separate from the regular kmalloc allocations. The need for proper
accounting of dcache external names has shown it's easy for misbehaving
process to allocate lots of them, causing premature OOMs. Without the
added grouping, it's likely that a similar workload can interleave the
dcache external names allocations with regular kmalloc allocations (note:
I haven't searched myself for an example of such regular kmalloc
allocation, but I would be very surprised if there wasn't some). A
pathological case would be e.g. one 64byte regular allocations with 63
external dcache names in a page (64x64=4096), which means the page is not
freed even after reclaiming after all dcache names, and the process can
thus "steal" the whole page with single 64byte allocation.
If other kmalloc users similar to dcache external names become identified,
they can also benefit from the new functionality simply by adding
__GFP_RECLAIMABLE to the kmalloc calls.
Side benefits of the patchset (that could be also merged separately)
include removed branch for detecting __GFP_DMA kmalloc(), and shortening
kmalloc cache names in /proc/slabinfo output. The latter is potentially
an ABI break in case there are tools parsing the names and expecting the
values to be in bytes.
This is how /proc/slabinfo looks like after booting in virtme:
...
kmalloc-rcl-4M 0 0 4194304 1 1024 : tunables 1 1 0 : slabdata 0 0 0
...
kmalloc-rcl-96 7 32 128 32 1 : tunables 120 60 8 : slabdata 1 1 0
kmalloc-rcl-64 25 128 64 64 1 : tunables 120 60 8 : slabdata 2 2 0
kmalloc-rcl-32 0 0 32 124 1 : tunables 120 60 8 : slabdata 0 0 0
kmalloc-4M 0 0 4194304 1 1024 : tunables 1 1 0 : slabdata 0 0 0
kmalloc-2M 0 0 2097152 1 512 : tunables 1 1 0 : slabdata 0 0 0
kmalloc-1M 0 0 1048576 1 256 : tunables 1 1 0 : slabdata 0 0 0
...
/proc/vmstat with renamed nr_indirectly_reclaimable_bytes counter:
...
nr_slab_reclaimable 2817
nr_slab_unreclaimable 1781
...
nr_kernel_misc_reclaimable 0
...
/proc/meminfo with new KReclaimable counter:
...
Shmem: 564 kB
KReclaimable: 11260 kB
Slab: 18368 kB
SReclaimable: 11260 kB
SUnreclaim: 7108 kB
KernelStack: 1248 kB
...
This patch (of 6):
The kmalloc caches currently mainain separate (optional) array
kmalloc_dma_caches for __GFP_DMA allocations. There are tests for
__GFP_DMA in the allocation hotpaths. We can avoid the branches by
combining kmalloc_caches and kmalloc_dma_caches into a single
two-dimensional array where the outer dimension is cache "type". This
will also allow to add kmalloc-reclaimable caches as a third type.
Link: http://lkml.kernel.org/r/20180731090649.16028-2-vbabka@suse.cz
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: Roman Gushchin <guro@fb.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Cc: Vijayanand Jitta <vjitta@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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get_mempolicy(MPOL_F_NODE|MPOL_F_ADDR) called a get_user_pages that would
not be waiting for userfaults before failing and it would hit on a SIGBUS
instead. Using get_user_pages_locked/unlocked instead will allow
get_mempolicy to allow userfaults to resolve the fault and fill the hole,
before grabbing the node id of the page.
If the user calls get_mempolicy() with MPOL_F_ADDR | MPOL_F_NODE for an
address inside an area managed by uffd and there is no page at that
address, the page allocation from within get_mempolicy() will fail
because get_user_pages() does not allow for page fault retry required
for uffd; the user will get SIGBUS.
With this patch, the page fault will be resolved by the uffd and the
get_mempolicy() will continue normally.
Background:
Via code review, previously the syscall would have returned -EFAULT
(vm_fault_to_errno), now it will block and wait for an userfault (if
it's waken before the fault is resolved it'll still -EFAULT).
This way get_mempolicy will give a chance to an "unaware" app to be
compliant with userfaults.
The reason this visible change is that becoming "userfault compliant"
cannot regress anything: all other syscalls including read(2)/write(2)
had to become "userfault compliant" long time ago (that's one of the
things userfaultfd can do that PROT_NONE and trapping segfaults can't).
So this is just one more syscall that become "userfault compliant" like
all other major ones already were.
This has been happening on virtio-bridge dpdk process which just called
get_mempolicy on the guest space post live migration, but before the
memory had a chance to be migrated to destination.
I didn't run an strace to be able to show the -EFAULT going away, but
I've the confirmation of the below debug aid information (only visible
with CONFIG_DEBUG_VM=y) going away with the patch:
[20116.371461] FAULT_FLAG_ALLOW_RETRY missing 0
[20116.371464] CPU: 1 PID: 13381 Comm: vhost-events Not tainted 4.17.12-200.fc28.x86_64 #1
[20116.371465] Hardware name: LENOVO 20FAS2BN0A/20FAS2BN0A, BIOS N1CET54W (1.22 ) 02/10/2017
[20116.371466] Call Trace:
[20116.371473] dump_stack+0x5c/0x80
[20116.371476] handle_userfault.cold.37+0x1b/0x22
[20116.371479] ? remove_wait_queue+0x20/0x60
[20116.371481] ? poll_freewait+0x45/0xa0
[20116.371483] ? do_sys_poll+0x31c/0x520
[20116.371485] ? radix_tree_lookup_slot+0x1e/0x50
[20116.371488] shmem_getpage_gfp+0xce7/0xe50
[20116.371491] ? page_add_file_rmap+0x1a/0x2c0
[20116.371493] shmem_fault+0x78/0x1e0
[20116.371495] ? filemap_map_pages+0x3a1/0x450
[20116.371498] __do_fault+0x1f/0xc0
[20116.371500] __handle_mm_fault+0xe2e/0x12f0
[20116.371502] handle_mm_fault+0xda/0x200
[20116.371504] __get_user_pages+0x238/0x790
[20116.371506] get_user_pages+0x3e/0x50
[20116.371510] kernel_get_mempolicy+0x40b/0x700
[20116.371512] ? vfs_write+0x170/0x1a0
[20116.371515] __x64_sys_get_mempolicy+0x21/0x30
[20116.371517] do_syscall_64+0x5b/0x160
[20116.371520] entry_SYSCALL_64_after_hwframe+0x44/0xa9
The above harmless debug message (not a kernel crash, just a
dump_stack()) is shown with CONFIG_DEBUG_VM=y to more quickly identify
and improve kernel spots that may have to become "userfaultfd
compliant" like this one (without having to run an strace and search
for syscall misbehavior). Spots like the above are more closer to a
kernel bug for the non-cooperative usages that Mike focuses on, than
for for dpdk qemu-cooperative usages that reproduced it, but it's still
nicer to get this fixed for dpdk too.
The part of the patch that caused me to think is only the
implementation issue of mpol_get, but it looks like it should work safe
no matter the kind of mempolicy structure that is (the default static
policy also starts at 1 so it'll go to 2 and back to 1 without crashing
everything at 0).
[rppt@linux.vnet.ibm.com: changelog addition]
http://lkml.kernel.org/r/20180904073718.GA26916@rapoport-lnx
Link: http://lkml.kernel.org/r/20180831214848.23676-1-aarcange@redhat.com
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Reported-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Tested-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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All callers convert its errno into a vm_fault_t, so convert it to return a
vm_fault_t directly.
Link: http://lkml.kernel.org/r/20180828145728.11873-11-willy@infradead.org
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Both of its callers currently convert its errno return into a vm_fault_t,
so move the conversion into __vm_insert_mixed().
Link: http://lkml.kernel.org/r/20180828145728.11873-10-willy@infradead.org
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
vm_insert_pfn_prot() is only called from vmf_insert_pfn_prot(), so inline
it and convert some of the errnos into vm_fault codes earlier.
Link: http://lkml.kernel.org/r/20180828145728.11873-9-willy@infradead.org
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
All callers are now converted to vmf_insert_pfn() so convert
vmf_insert_pfn() from being a compatibility wrapper around vm_insert_pfn()
to being a compatibility wrapper around vmf_insert_pfn_prot().
Link: http://lkml.kernel.org/r/20180828145728.11873-8-willy@infradead.org
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Now this is no longer used outside mm/memory.c, make it static.
Link: http://lkml.kernel.org/r/20180828145728.11873-6-willy@infradead.org
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Like vm_insert_pfn_prot(), but returns a vm_fault_t instead of an errno.
Also unexport vm_insert_pfn_prot as it has no modular users.
Link: http://lkml.kernel.org/r/20180828145728.11873-4-willy@infradead.org
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
All callers are now converted to vmf_insert_mixed() so convert
vmf_insert_mixed() from being a compatibility wrapper into the real
function.
Link: http://lkml.kernel.org/r/20180828145728.11873-3-willy@infradead.org
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
As part of vm_fault_t conversion filemap_page_mkwrite() for the NOMMU case
was missed. Now converted.
Link: http://lkml.kernel.org/r/20180828174952.GA29229@jordon-HP-15-Notebook-PC
Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
check_for_memory() looks a bit confusing. First of all, we have this:
if (N_MEMORY == N_NORMAL_MEMORY)
return;
Checking the ENUM declaration, looks like N_MEMORY canot be equal to
N_NORMAL_MEMORY.
I could not find where N_MEMORY is set to N_NORMAL_MEMORY, or the other
way around either, so unless I am missing something, this condition will
never evaluate to true. It makes sense to get rid of it.
Moving forward, the operations within the loop look a bit confusing as
well.
We set N_HIGH_MEMORY unconditionally, and then we set N_NORMAL_MEMORY in
case we have CONFIG_HIGHMEM (N_NORMAL_MEMORY != N_HIGH_MEMORY) and zone <=
ZONE_NORMAL. (N_HIGH_MEMORY falls back to N_NORMAL_MEMORY on
!CONFIG_HIGHMEM systems, and that is why we can just go ahead and set
N_HIGH_MEMORY unconditionally)
Although this works, it is a bit subtle.
I think that this could be easier to follow:
First, we should only set N_HIGH_MEMORY in case we have CONFIG_HIGHMEM.
And then we should set N_NORMAL_MEMORY in case zone <= ZONE_NORMAL,
without further checking whether we have CONFIG_HIGHMEM or not.
Link: http://lkml.kernel.org/r/20180828210158.4617-1-osalvador@techadventures.net
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Michael Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Pavel Tatashin <pavel.tatashin@microsoft.com
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
si->swap_map[] of the swap entries in cluster needs to be cleared during
freeing. Previously, this is done in the caller of swap_free_cluster().
This may cause code duplication (one user now, will add more users later)
and lock/unlock cluster unnecessarily. In this patch, the clearing code
is moved to swap_free_cluster() to avoid the downside.
Link: http://lkml.kernel.org/r/20180827075535.17406-4-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Shaohua Li <shli@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
This is a code cleanup patch without functionality change.
Originally, when __swap_entry_free() is called, and its return value is 0,
free_swap_slot() will always be called to free the swap entry to the
per-CPU pool. So move the call to free_swap_slot() to __swap_entry_free()
to simplify the code.
Link: http://lkml.kernel.org/r/20180827075535.17406-3-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Shaohua Li <shli@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
The code path to reclaim the swap entry in free_swap_and_cache() is
almost same as that of __try_to_reclaim_swap(). The largest
difference is just coding style. So the support to the additional
requirement of free_swap_and_cache() is added into
__try_to_reclaim_swap(). free_swap_and_cache() is changed to call
__try_to_reclaim_swap(), and delete the duplicated code. This will
improve code readability and reduce the potential bugs.
There are 2 functionality differences between __try_to_reclaim_swap()
and swap entry reclaim code of free_swap_and_cache().
- free_swap_and_cache() only reclaims the swap entry if the page is
unmapped or swap is getting full. The support has been added into
__try_to_reclaim_swap().
- try_to_free_swap() (called by __try_to_reclaim_swap()) checks
pm_suspended_storage(), while free_swap_and_cache() not. I think
this is OK. Because the page and the swap entry can be reclaimed
later eventually.
Link: http://lkml.kernel.org/r/20180827075535.17406-2-ying.huang@intel.com
Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Shaohua Li <shli@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Currently, kmemleak only prints the number of suspected leaks to dmesg but
requires the user to read a debugfs file to get the actual stack traces of
the objects' allocation points. Add a module option to print the full
object information to dmesg too. It can be enabled with
kmemleak.verbose=1 on the kernel command line, or "echo 1 >
/sys/module/kmemleak/parameters/verbose":
This allows easier integration of kmemleak into test systems: We have
automated test infrastructure to test our Linux systems. With this
option, running our tests with kmemleak is as simple as enabling kmemleak
and passing this command line option; the test infrastructure knows how to
save kernel logs, which will now include kmemleak reports. Without this
option, the test infrastructure needs to be specifically taught to read
out the kmemleak debugfs file. Removing this need for special handling
makes kmemleak more similar to other kernel debug options (slab debugging,
debug objects, etc).
Link: http://lkml.kernel.org/r/20180903144046.21023-1-vincent.whitchurch@axis.com
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
callbacks"
Revert 5ff7091f5a2ca ("mm, mmu_notifier: annotate mmu notifiers with
blockable invalidate callbacks").
MMU_INVALIDATE_DOES_NOT_BLOCK flags was the only one used and it is no
longer needed since 93065ac753e4 ("mm, oom: distinguish blockable mode for
mmu notifiers"). We now have a full support for per range !blocking
behavior so we can drop the stop gap workaround which the per notifier
flag was used for.
Link: http://lkml.kernel.org/r/20180827112623.8992-4-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Tetsuo Handa has reported that it is possible to bypass the short sleep
for PF_WQ_WORKER threads which was introduced by commit 373ccbe5927034b5
("mm, vmstat: allow WQ concurrency to discover memory reclaim doesn't make
any progress") and lock up the system if OOM.
The primary reason is that WQ_MEM_RECLAIM WQs are not guaranteed to run
even when they have a rescuer available. Those workers might be essential
for reclaim to make a forward progress, however. If we are too unlucky
all the allocations requests can get stuck waiting for a WQ_MEM_RECLAIM
work item and the system is essentially stuck in an OOM condition without
much hope to move on. Tetsuo has seen the reclaim stuck on
drain_local_pages_wq or xlog_cil_push_work (xfs). There might be others.
Since should_reclaim_retry() should be a natural reschedule point,
let's do the short sleep for PF_WQ_WORKER threads unconditionally in
order to guarantee that other pending work items are started. This
will workaround this problem and it is less fragile than hunting down
when the sleep is missed. Having a single sleeping point is more
robust.
[akpm@linux-foundation.org: reflow comment to 80 cols to save a couple of lines]
Link: http://lkml.kernel.org/r/20180827135101.15700-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Debugged-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
I've noticed, that dying memory cgroups are often pinned in memory by a
single pagecache page. Even under moderate memory pressure they sometimes
stayed in such state for a long time. That looked strange.
My investigation showed that the problem is caused by applying the LRU
pressure balancing math:
scan = div64_u64(scan * fraction[lru], denominator),
where
denominator = fraction[anon] + fraction[file] + 1.
Because fraction[lru] is always less than denominator, if the initial scan
size is 1, the result is always 0.
This means the last page is not scanned and has
no chances to be reclaimed.
Fix this by rounding up the result of the division.
In practice this change significantly improves the speed of dying cgroups
reclaim.
[guro@fb.com: prevent double calculation of DIV64_U64_ROUND_UP() arguments]
Link: http://lkml.kernel.org/r/20180829213311.GA13501@castle
Link: http://lkml.kernel.org/r/20180827162621.30187-3-guro@fb.com
Signed-off-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Memcg charge is batched using per-cpu stocks, so an offline memcg can be
pinned by a cached charge up to a moment, when a process belonging to some
other cgroup will charge some memory on the same cpu. In other words,
cached charges can prevent a memory cgroup from being reclaimed for some
time, without any clear need.
Let's optimize it by explicit draining of all stocks on css offlining. As
draining is performed asynchronously, and is skipped if any parallel
draining is happening, it's cheap.
Link: http://lkml.kernel.org/r/20180827162621.30187-2-guro@fb.com
Signed-off-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Michal Hocko <mhocko@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Extend the slub_debug syntax to "slub_debug=<flags>[,<slub>]*", where
<slub> may contain an asterisk at the end. For example, the following
would poison all kmalloc slabs:
slub_debug=P,kmalloc*
and the following would apply the default flags to all kmalloc and all
block IO slabs:
slub_debug=,bio*,kmalloc*
Please note that a similar patch was posted by Iliyan Malchev some time
ago but was never merged:
https://marc.info/?l=linux-mm&m=131283905330474&w=2
Link: http://lkml.kernel.org/r/20180928111139.27962-1-atomlin@redhat.com
Signed-off-by: Aaron Tomlin <atomlin@redhat.com>
Acked-by: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Iliyan Malchev <malchev@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Slub does not call kmalloc_slab() for sizes > KMALLOC_MAX_CACHE_SIZE,
instead it falls back to kmalloc_large().
For slab KMALLOC_MAX_CACHE_SIZE == KMALLOC_MAX_SIZE and it calls
kmalloc_slab() for all allocations relying on NULL return value for
over-sized allocations.
This inconsistency leads to unwanted warnings from kmalloc_slab() for
over-sized allocations for slab. Returning NULL for failed allocations is
the expected behavior.
Make slub and slab code consistent by checking size >
KMALLOC_MAX_CACHE_SIZE in slab before calling kmalloc_slab().
While we are here also fix the check in kmalloc_slab(). We should check
against KMALLOC_MAX_CACHE_SIZE rather than KMALLOC_MAX_SIZE. It all kinda
worked because for slab the constants are the same, and slub always checks
the size against KMALLOC_MAX_CACHE_SIZE before kmalloc_slab(). But if we
get there with size > KMALLOC_MAX_CACHE_SIZE anyhow bad things will
happen. For example, in case of a newly introduced bug in slub code.
Also move the check in kmalloc_slab() from function entry to the size >
192 case. This partially compensates for the additional check in slab
code and makes slub code a bit faster (at least theoretically).
Also drop __GFP_NOWARN in the warning check. This warning means a bug in
slab code itself, user-passed flags have nothing to do with it.
Nothing of this affects slob.
Link: http://lkml.kernel.org/r/20180927171502.226522-1-dvyukov@gmail.com
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Reported-by: syzbot+87829a10073277282ad1@syzkaller.appspotmail.com
Reported-by: syzbot+ef4e8fc3a06e9019bb40@syzkaller.appspotmail.com
Reported-by: syzbot+6e438f4036df52cbb863@syzkaller.appspotmail.com
Reported-by: syzbot+8574471d8734457d98aa@syzkaller.appspotmail.com
Reported-by: syzbot+af1504df0807a083dbd9@syzkaller.appspotmail.com
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
Switch to bitmap_zalloc() to show clearly what we are allocating. Besides
that it returns pointer of bitmap type instead of opaque void *.
Link: http://lkml.kernel.org/r/20180830104301.61649-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Christoph Lameter <cl@linux.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Tested-by: David Rientjes <rientjes@google.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core
Pull driver core updates from Greg KH:
"Here is a small number of driver core patches for 4.20-rc1.
Not much happened here this merge window, only a very tiny number of
patches that do:
- add BUS_ATTR_WO() for use by drivers
- component error path fixes
- kernfs range check fix
- other tiny error path fixes and const changes
All of these have been in linux-next with no reported issues for a
while"
* tag 'driver-core-4.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
devres: provide devm_kstrdup_const()
mm: move is_kernel_rodata() to asm-generic/sections.h
devres: constify p in devm_kfree()
driver core: add BUS_ATTR_WO() macro
kernfs: Fix range checks in kernfs_get_target_path
component: fix loop condition to call unbind() if bind() fails
drivers/base/devtmpfs.c: don't pretend path is const in delete_path
kernfs: update comment about kernfs_path() return value
|
|
git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull siginfo updates from Eric Biederman:
"I have been slowly sorting out siginfo and this is the culmination of
that work.
The primary result is in several ways the signal infrastructure has
been made less error prone. The code has been updated so that manually
specifying SEND_SIG_FORCED is never necessary. The conversion to the
new siginfo sending functions is now complete, which makes it
difficult to send a signal without filling in the proper siginfo
fields.
At the tail end of the patchset comes the optimization of decreasing
the size of struct siginfo in the kernel from 128 bytes to about 48
bytes on 64bit. The fundamental observation that enables this is by
definition none of the known ways to use struct siginfo uses the extra
bytes.
This comes at the cost of a small user space observable difference.
For the rare case of siginfo being injected into the kernel only what
can be copied into kernel_siginfo is delivered to the destination, the
rest of the bytes are set to 0. For cases where the signal and the
si_code are known this is safe, because we know those bytes are not
used. For cases where the signal and si_code combination is unknown
the bits that won't fit into struct kernel_siginfo are tested to
verify they are zero, and the send fails if they are not.
I made an extensive search through userspace code and I could not find
anything that would break because of the above change. If it turns out
I did break something it will take just the revert of a single change
to restore kernel_siginfo to the same size as userspace siginfo.
Testing did reveal dependencies on preferring the signo passed to
sigqueueinfo over si->signo, so bit the bullet and added the
complexity necessary to handle that case.
Testing also revealed bad things can happen if a negative signal
number is passed into the system calls. Something no sane application
will do but something a malicious program or a fuzzer might do. So I
have fixed the code that performs the bounds checks to ensure negative
signal numbers are handled"
* 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (80 commits)
signal: Guard against negative signal numbers in copy_siginfo_from_user32
signal: Guard against negative signal numbers in copy_siginfo_from_user
signal: In sigqueueinfo prefer sig not si_signo
signal: Use a smaller struct siginfo in the kernel
signal: Distinguish between kernel_siginfo and siginfo
signal: Introduce copy_siginfo_from_user and use it's return value
signal: Remove the need for __ARCH_SI_PREABLE_SIZE and SI_PAD_SIZE
signal: Fail sigqueueinfo if si_signo != sig
signal/sparc: Move EMT_TAGOVF into the generic siginfo.h
signal/unicore32: Use force_sig_fault where appropriate
signal/unicore32: Generate siginfo in ucs32_notify_die
signal/unicore32: Use send_sig_fault where appropriate
signal/arc: Use force_sig_fault where appropriate
signal/arc: Push siginfo generation into unhandled_exception
signal/ia64: Use force_sig_fault where appropriate
signal/ia64: Use the force_sig(SIGSEGV,...) in ia64_rt_sigreturn
signal/ia64: Use the generic force_sigsegv in setup_frame
signal/arm/kvm: Use send_sig_mceerr
signal/arm: Use send_sig_fault where appropriate
signal/arm: Use force_sig_fault where appropriate
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 mm updates from Ingo Molnar:
"Lots of changes in this cycle:
- Lots of CPA (change page attribute) optimizations and related
cleanups (Thomas Gleixner, Peter Zijstra)
- Make lazy TLB mode even lazier (Rik van Riel)
- Fault handler cleanups and improvements (Dave Hansen)
- kdump, vmcore: Enable kdumping encrypted memory with AMD SME
enabled (Lianbo Jiang)
- Clean up VM layout documentation (Baoquan He, Ingo Molnar)
- ... plus misc other fixes and enhancements"
* 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (51 commits)
x86/stackprotector: Remove the call to boot_init_stack_canary() from cpu_startup_entry()
x86/mm: Kill stray kernel fault handling comment
x86/mm: Do not warn about PCI BIOS W+X mappings
resource: Clean it up a bit
resource: Fix find_next_iomem_res() iteration issue
resource: Include resource end in walk_*() interfaces
x86/kexec: Correct KEXEC_BACKUP_SRC_END off-by-one error
x86/mm: Remove spurious fault pkey check
x86/mm/vsyscall: Consider vsyscall page part of user address space
x86/mm: Add vsyscall address helper
x86/mm: Fix exception table comments
x86/mm: Add clarifying comments for user addr space
x86/mm: Break out user address space handling
x86/mm: Break out kernel address space handling
x86/mm: Clarify hardware vs. software "error_code"
x86/mm/tlb: Make lazy TLB mode lazier
x86/mm/tlb: Add freed_tables element to flush_tlb_info
x86/mm/tlb: Add freed_tables argument to flush_tlb_mm_range
smp,cpumask: introduce on_each_cpu_cond_mask
smp: use __cpumask_set_cpu in on_each_cpu_cond
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking and misc x86 updates from Ingo Molnar:
"Lots of changes in this cycle - in part because locking/core attracted
a number of related x86 low level work which was easier to handle in a
single tree:
- Linux Kernel Memory Consistency Model updates (Alan Stern, Paul E.
McKenney, Andrea Parri)
- lockdep scalability improvements and micro-optimizations (Waiman
Long)
- rwsem improvements (Waiman Long)
- spinlock micro-optimization (Matthew Wilcox)
- qspinlocks: Provide a liveness guarantee (more fairness) on x86.
(Peter Zijlstra)
- Add support for relative references in jump tables on arm64, x86
and s390 to optimize jump labels (Ard Biesheuvel, Heiko Carstens)
- Be a lot less permissive on weird (kernel address) uaccess faults
on x86: BUG() when uaccess helpers fault on kernel addresses (Jann
Horn)
- macrofy x86 asm statements to un-confuse the GCC inliner. (Nadav
Amit)
- ... and a handful of other smaller changes as well"
* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (57 commits)
locking/lockdep: Make global debug_locks* variables read-mostly
locking/lockdep: Fix debug_locks off performance problem
locking/pvqspinlock: Extend node size when pvqspinlock is configured
locking/qspinlock_stat: Count instances of nested lock slowpaths
locking/qspinlock, x86: Provide liveness guarantee
x86/asm: 'Simplify' GEN_*_RMWcc() macros
locking/qspinlock: Rework some comments
locking/qspinlock: Re-order code
locking/lockdep: Remove duplicated 'lock_class_ops' percpu array
x86/defconfig: Enable CONFIG_USB_XHCI_HCD=y
futex: Replace spin_is_locked() with lockdep
locking/lockdep: Make class->ops a percpu counter and move it under CONFIG_DEBUG_LOCKDEP=y
x86/jump-labels: Macrofy inline assembly code to work around GCC inlining bugs
x86/cpufeature: Macrofy inline assembly code to work around GCC inlining bugs
x86/extable: Macrofy inline assembly code to work around GCC inlining bugs
x86/paravirt: Work around GCC inlining bugs when compiling paravirt ops
x86/bug: Macrofy the BUG table section handling, to work around GCC inlining bugs
x86/alternatives: Macrofy lock prefixes to work around GCC inlining bugs
x86/refcount: Work around GCC inlining bug
x86/objtool: Use asm macros to work around GCC inlining bugs
...
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Pull block layer updates from Jens Axboe:
"This is the main pull request for block changes for 4.20. This
contains:
- Series enabling runtime PM for blk-mq (Bart).
- Two pull requests from Christoph for NVMe, with items such as;
- Better AEN tracking
- Multipath improvements
- RDMA fixes
- Rework of FC for target removal
- Fixes for issues identified by static checkers
- Fabric cleanups, as prep for TCP transport
- Various cleanups and bug fixes
- Block merging cleanups (Christoph)
- Conversion of drivers to generic DMA mapping API (Christoph)
- Series fixing ref count issues with blkcg (Dennis)
- Series improving BFQ heuristics (Paolo, et al)
- Series improving heuristics for the Kyber IO scheduler (Omar)
- Removal of dangerous bio_rewind_iter() API (Ming)
- Apply single queue IPI redirection logic to blk-mq (Ming)
- Set of fixes and improvements for bcache (Coly et al)
- Series closing a hotplug race with sysfs group attributes (Hannes)
- Set of patches for lightnvm:
- pblk trace support (Hans)
- SPDX license header update (Javier)
- Tons of refactoring patches to cleanly abstract the 1.2 and 2.0
specs behind a common core interface. (Javier, Matias)
- Enable pblk to use a common interface to retrieve chunk metadata
(Matias)
- Bug fixes (Various)
- Set of fixes and updates to the blk IO latency target (Josef)
- blk-mq queue number updates fixes (Jianchao)
- Convert a bunch of drivers from the old legacy IO interface to
blk-mq. This will conclude with the removal of the legacy IO
interface itself in 4.21, with the rest of the drivers (me, Omar)
- Removal of the DAC960 driver. The SCSI tree will introduce two
replacement drivers for this (Hannes)"
* tag 'for-4.20/block-20181021' of git://git.kernel.dk/linux-block: (204 commits)
block: setup bounce bio_sets properly
blkcg: reassociate bios when make_request() is called recursively
blkcg: fix edge case for blk_get_rl() under memory pressure
nvme-fabrics: move controller options matching to fabrics
nvme-rdma: always have a valid trsvcid
mtip32xx: fully switch to the generic DMA API
rsxx: switch to the generic DMA API
umem: switch to the generic DMA API
sx8: switch to the generic DMA API
sx8: remove dead IF_64BIT_DMA_IS_POSSIBLE code
skd: switch to the generic DMA API
ubd: remove use of blk_rq_map_sg
nvme-pci: remove duplicate check
drivers/block: Remove DAC960 driver
nvme-pci: fix hot removal during error handling
nvmet-fcloop: suppress a compiler warning
nvme-core: make implicit seed truncation explicit
nvmet-fc: fix kernel-doc headers
nvme-fc: rework the request initialization code
nvme-fc: introduce struct nvme_fcp_op_w_sgl
...
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git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
Pull arm64 updates from Catalin Marinas:
"Apart from some new arm64 features and clean-ups, this also contains
the core mmu_gather changes for tracking the levels of the page table
being cleared and a minor update to the generic
compat_sys_sigaltstack() introducing COMPAT_SIGMINSKSZ.
Summary:
- Core mmu_gather changes which allow tracking the levels of
page-table being cleared together with the arm64 low-level flushing
routines
- Support for the new ARMv8.5 PSTATE.SSBS bit which can be used to
mitigate Spectre-v4 dynamically without trapping to EL3 firmware
- Introduce COMPAT_SIGMINSTKSZ for use in compat_sys_sigaltstack
- Optimise emulation of MRS instructions to ID_* registers on ARMv8.4
- Support for Common Not Private (CnP) translations allowing threads
of the same CPU to share the TLB entries
- Accelerated crc32 routines
- Move swapper_pg_dir to the rodata section
- Trap WFI instruction executed in user space
- ARM erratum 1188874 workaround (arch_timer)
- Miscellaneous fixes and clean-ups"
* tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (78 commits)
arm64: KVM: Guests can skip __install_bp_hardening_cb()s HYP work
arm64: cpufeature: Trap CTR_EL0 access only where it is necessary
arm64: cpufeature: Fix handling of CTR_EL0.IDC field
arm64: cpufeature: ctr: Fix cpu capability check for late CPUs
Documentation/arm64: HugeTLB page implementation
arm64: mm: Use __pa_symbol() for set_swapper_pgd()
arm64: Add silicon-errata.txt entry for ARM erratum 1188873
Revert "arm64: uaccess: implement unsafe accessors"
arm64: mm: Drop the unused cpu parameter
MAINTAINERS: fix bad sdei paths
arm64: mm: Use #ifdef for the __PAGETABLE_P?D_FOLDED defines
arm64: Fix typo in a comment in arch/arm64/mm/kasan_init.c
arm64: xen: Use existing helper to check interrupt status
arm64: Use daifflag_restore after bp_hardening
arm64: daifflags: Use irqflags functions for daifflags
arm64: arch_timer: avoid unused function warning
arm64: Trap WFI executed in userspace
arm64: docs: Document SSBS HWCAP
arm64: docs: Fix typos in ELF hwcaps
arm64/kprobes: remove an extra semicolon in arch_prepare_kprobe
...
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Jann Horn points out that our TLB flushing was subtly wrong for the
mremap() case. What makes mremap() special is that we don't follow the
usual "add page to list of pages to be freed, then flush tlb, and then
free pages". No, mremap() obviously just _moves_ the page from one page
table location to another.
That matters, because mremap() thus doesn't directly control the
lifetime of the moved page with a freelist: instead, the lifetime of the
page is controlled by the page table locking, that serializes access to
the entry.
As a result, we need to flush the TLB not just before releasing the lock
for the source location (to avoid any concurrent accesses to the entry),
but also before we release the destination page table lock (to avoid the
TLB being flushed after somebody else has already done something to that
page).
This also makes the whole "need_flush" logic unnecessary, since we now
always end up flushing the TLB for every valid entry.
Reported-and-tested-by: Jann Horn <jannh@google.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Tested-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Export this routine so that we can use it later in devm_kstrdup_const()
and devm_kfree().
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Acked-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Acked-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Inside set_pmd_migration_entry() we are holding page table locks and thus
we can not sleep so we can not call invalidate_range_start/end()
So remove call to mmu_notifier_invalidate_range_start/end() because they
are call inside the function calling set_pmd_migration_entry() (see
try_to_unmap_one()).
Link: http://lkml.kernel.org/r/20181012181056.7864-1-jglisse@redhat.com
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Reported-by: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Zi Yan <zi.yan@cs.rutgers.edu>
Acked-by: Michal Hocko <mhocko@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: David Nellans <dnellans@nvidia.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Daniel Micay reports that attempting to use MAP_FIXED_NOREPLACE in an
application causes that application to randomly crash. The existing check
for handling MAP_FIXED_NOREPLACE looks up the first VMA that either
overlaps or follows the requested region, and then bails out if that VMA
overlaps *the start* of the requested region. It does not bail out if the
VMA only overlaps another part of the requested region.
Fix it by checking that the found VMA only starts at or after the end of
the requested region, in which case there is no overlap.
Test case:
user@debian:~$ cat mmap_fixed_simple.c
#include <sys/mman.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#ifndef MAP_FIXED_NOREPLACE
#define MAP_FIXED_NOREPLACE 0x100000
#endif
int main(void) {
char *p;
errno = 0;
p = mmap((void*)0x10001000, 0x4000, PROT_NONE,
MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED_NOREPLACE, -1, 0);
printf("p1=%p err=%m\n", p);
errno = 0;
p = mmap((void*)0x10000000, 0x2000, PROT_READ,
MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED_NOREPLACE, -1, 0);
printf("p2=%p err=%m\n", p);
char cmd[100];
sprintf(cmd, "cat /proc/%d/maps", getpid());
system(cmd);
return 0;
}
user@debian:~$ gcc -o mmap_fixed_simple mmap_fixed_simple.c
user@debian:~$ ./mmap_fixed_simple
p1=0x10001000 err=Success
p2=0x10000000 err=Success
10000000-10002000 r--p 00000000 00:00 0
10002000-10005000 ---p 00000000 00:00 0
564a9a06f000-564a9a070000 r-xp 00000000 fe:01 264004
/home/user/mmap_fixed_simple
564a9a26f000-564a9a270000 r--p 00000000 fe:01 264004
/home/user/mmap_fixed_simple
564a9a270000-564a9a271000 rw-p 00001000 fe:01 264004
/home/user/mmap_fixed_simple
564a9a54a000-564a9a56b000 rw-p 00000000 00:00 0 [heap]
7f8eba447000-7f8eba5dc000 r-xp 00000000 fe:01 405885
/lib/x86_64-linux-gnu/libc-2.24.so
7f8eba5dc000-7f8eba7dc000 ---p 00195000 fe:01 405885
/lib/x86_64-linux-gnu/libc-2.24.so
7f8eba7dc000-7f8eba7e0000 r--p 00195000 fe:01 405885
/lib/x86_64-linux-gnu/libc-2.24.so
7f8eba7e0000-7f8eba7e2000 rw-p 00199000 fe:01 405885
/lib/x86_64-linux-gnu/libc-2.24.so
7f8eba7e2000-7f8eba7e6000 rw-p 00000000 00:00 0
7f8eba7e6000-7f8eba809000 r-xp 00000000 fe:01 405876
/lib/x86_64-linux-gnu/ld-2.24.so
7f8eba9e9000-7f8eba9eb000 rw-p 00000000 00:00 0
7f8ebaa06000-7f8ebaa09000 rw-p 00000000 00:00 0
7f8ebaa09000-7f8ebaa0a000 r--p 00023000 fe:01 405876
/lib/x86_64-linux-gnu/ld-2.24.so
7f8ebaa0a000-7f8ebaa0b000 rw-p 00024000 fe:01 405876
/lib/x86_64-linux-gnu/ld-2.24.so
7f8ebaa0b000-7f8ebaa0c000 rw-p 00000000 00:00 0
7ffcc99fa000-7ffcc9a1b000 rw-p 00000000 00:00 0 [stack]
7ffcc9b44000-7ffcc9b47000 r--p 00000000 00:00 0 [vvar]
7ffcc9b47000-7ffcc9b49000 r-xp 00000000 00:00 0 [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0
[vsyscall]
user@debian:~$ uname -a
Linux debian 4.19.0-rc6+ #181 SMP Wed Oct 3 23:43:42 CEST 2018 x86_64 GNU/Linux
user@debian:~$
As you can see, the first page of the mapping at 0x10001000 was clobbered.
Link: http://lkml.kernel.org/r/20181010152736.99475-1-jannh@google.com
Fixes: a4ff8e8620d3 ("mm: introduce MAP_FIXED_NOREPLACE")
Signed-off-by: Jann Horn <jannh@google.com>
Reported-by: Daniel Micay <danielmicay@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: John Hubbard <jhubbard@nvidia.com>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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