diff options
| author | Ryan Roberts <ryan.roberts@arm.com> | 2024-07-04 10:10:50 +0100 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2024-07-12 15:52:20 -0700 |
| commit | 00f58104202c472e487f0866fbd38832523fd4f9 (patch) | |
| tree | fe8cfb3123a3867e7d0b25a381e0e3c253ac8d89 /mm/huge_memory.c | |
| parent | 823430c8e9d98c5865af518c782d0493b76aa511 (diff) | |
mm: fix khugepaged activation policy
Since the introduction of mTHP, the docuementation has stated that
khugepaged would be enabled when any mTHP size is enabled, and disabled
when all mTHP sizes are disabled. There are 2 problems with this; 1.
this is not what was implemented by the code and 2. this is not the
desirable behavior.
Desirable behavior is for khugepaged to be enabled when any PMD-sized THP
is enabled, anon or file. (Note that file THP is still controlled by the
top-level control so we must always consider that, as well as the PMD-size
mTHP control for anon). khugepaged only supports collapsing to PMD-sized
THP so there is no value in enabling it when PMD-sized THP is disabled.
So let's change the code and documentation to reflect this policy.
Further, per-size enabled control modification events were not previously
forwarded to khugepaged to give it an opportunity to start or stop.
Consequently the following was resulting in khugepaged eroneously not
being activated:
echo never > /sys/kernel/mm/transparent_hugepage/enabled
echo always > /sys/kernel/mm/transparent_hugepage/hugepages-2048kB/enabled
[ryan.roberts@arm.com: v3]
Link: https://lkml.kernel.org/r/20240705102849.2479686-1-ryan.roberts@arm.com
Link: https://lkml.kernel.org/r/20240705102849.2479686-1-ryan.roberts@arm.com
Link: https://lkml.kernel.org/r/20240704091051.2411934-1-ryan.roberts@arm.com
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Fixes: 3485b88390b0 ("mm: thp: introduce multi-size THP sysfs interface")
Closes: https://lore.kernel.org/linux-mm/7a0bbe69-1e3d-4263-b206-da007791a5c4@redhat.com/
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/huge_memory.c')
| -rw-r--r-- | mm/huge_memory.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 17fb072a0ca1..f8b5cbd4dd71 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -502,6 +502,13 @@ static ssize_t thpsize_enabled_store(struct kobject *kobj, } else ret = -EINVAL; + if (ret > 0) { + int err; + + err = start_stop_khugepaged(); + if (err) + ret = err; + } return ret; } |