diff options
| author | Minchan Kim <minchan@kernel.org> | 2022-05-19 14:08:54 -0700 |
|---|---|---|
| committer | akpm <akpm@linux-foundation.org> | 2022-05-19 14:08:54 -0700 |
| commit | 6d4675e601357834dadd2ba1d803f6484596015c (patch) | |
| tree | 4cb1490901fa887fcb0d7ecc34629baa16a4ad18 /mm/vmscan.c | |
| parent | f4840ccfca25db225b3371a8f7b5770febee87c5 (diff) | |
mm: don't be stuck to rmap lock on reclaim path
The rmap locks(i_mmap_rwsem and anon_vma->root->rwsem) could be contended
under memory pressure if processes keep working on their vmas(e.g., fork,
mmap, munmap). It makes reclaim path stuck. In our real workload traces,
we see kswapd is waiting the lock for 300ms+(worst case, a sec) and it
makes other processes entering direct reclaim, which were also stuck on
the lock.
This patch makes lru aging path try_lock mode like shink_page_list so the
reclaim context will keep working with next lru pages without being stuck.
if it found the rmap lock contended, it rotates the page back to head of
lru in both active/inactive lrus to make them consistent behavior, which
is basic starting point rather than adding more heristic.
Since this patch introduces a new "contended" field as out-param along
with try_lock in-param in rmap_walk_control, it's not immutable any longer
if the try_lock is set so remove const keywords on rmap related functions.
Since rmap walking is already expensive operation, I doubt the const
would help sizable benefit( And we didn't have it until 5.17).
In a heavy app workload in Android, trace shows following statistics. It
almost removes rmap lock contention from reclaim path.
Martin Liu reported:
Before:
max_dur(ms) min_dur(ms) max-min(dur)ms avg_dur(ms) sum_dur(ms) count blocked_function
1632 0 1631 151.542173 31672 209 page_lock_anon_vma_read
601 0 601 145.544681 28817 198 rmap_walk_file
After:
max_dur(ms) min_dur(ms) max-min(dur)ms avg_dur(ms) sum_dur(ms) count blocked_function
NaN NaN NaN NaN NaN 0.0 NaN
0 0 0 0.127645 1 12 rmap_walk_file
[minchan@kernel.org: add comment, per Matthew]
Link: https://lkml.kernel.org/r/YnNqeB5tUf6LZ57b@google.com
Link: https://lkml.kernel.org/r/20220510215423.164547-1-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: John Dias <joaodias@google.com>
Cc: Tim Murray <timmurray@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Martin Liu <liumartin@google.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/vmscan.c')
| -rw-r--r-- | mm/vmscan.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c index 24dbe04520cb..887edcd93a40 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1391,6 +1391,10 @@ static enum page_references folio_check_references(struct folio *folio, if (vm_flags & VM_LOCKED) return PAGEREF_ACTIVATE; + /* rmap lock contention: rotate */ + if (referenced_ptes == -1) + return PAGEREF_KEEP; + if (referenced_ptes) { /* * All mapped folios start out with page table @@ -2499,8 +2503,9 @@ static void shrink_active_list(unsigned long nr_to_scan, } } + /* Referenced or rmap lock contention: rotate */ if (folio_referenced(folio, 0, sc->target_mem_cgroup, - &vm_flags)) { + &vm_flags) != 0) { /* * Identify referenced, file-backed active pages and * give them one more trip around the active list. So |