From 435b3894e74256cc93772b7e586d848a5c3433ee Mon Sep 17 00:00:00 2001 From: Zhongkun He Date: Thu, 22 Aug 2024 17:26:12 +0800 Subject: [PATCH] mm:page_alloc: fix the NULL ac->nodemask in __alloc_pages_slowpath() should_reclaim_retry() is not ALLOC_CPUSET aware and that means that it considers reclaimability of NUMA nodes which are outside of the cpuset. If other nodes have a lot of reclaimable memory then should_reclaim_retry would instruct page allocator to retry even though there is no memory reclaimable on the cpuset nodemask. This is not really a huge problem because the number of retries without any reclaim progress is bound but it could be certainly improved. This is a cold path so this shouldn't really have a measurable impact on performance on most workloads. 1.Test step and the machines. ------------ root@vm:/sys/fs/cgroup/test# numactl -H | grep size node 0 size: 9477 MB node 1 size: 10079 MB node 2 size: 10079 MB node 3 size: 10078 MB root@vm:/sys/fs/cgroup/test# cat cpuset.mems 2 root@vm:/sys/fs/cgroup/test# stress --vm 1 --vm-bytes 12g --vm-keep stress: info: [33430] dispatching hogs: 0 cpu, 0 io, 1 vm, 0 hdd stress: FAIL: [33430] (425) <-- worker 33431 got signal 9 stress: WARN: [33430] (427) now reaping child worker processes stress: FAIL: [33430] (461) failed run completed in 2s 2. reclaim_retry_zone info: We can only alloc pages from node=2, but the reclaim_retry_zone is node=0 and return true. root@vm:/sys/kernel/debug/tracing# cat trace stress-33431 [001] ..... 13223.617311: reclaim_retry_zone: node=0 zone=Normal order=0 reclaimable=4260 available=1772019 min_wmark=5962 no_progress_loops=1 wmark_check=1 stress-33431 [001] ..... 13223.617682: reclaim_retry_zone: node=0 zone=Normal order=0 reclaimable=4260 available=1772019 min_wmark=5962 no_progress_loops=2 wmark_check=1 stress-33431 [001] ..... 13223.618103: reclaim_retry_zone: node=0 zone=Normal order=0 reclaimable=4260 available=1772019 min_wmark=5962 no_progress_loops=3 wmark_check=1 stress-33431 [001] ..... 13223.618454: reclaim_retry_zone: node=0 zone=Normal order=0 reclaimable=4260 available=1772019 min_wmark=5962 no_progress_loops=4 wmark_check=1 stress-33431 [001] ..... 13223.618770: reclaim_retry_zone: node=0 zone=Normal order=0 reclaimable=4260 available=1772019 min_wmark=5962 no_progress_loops=5 wmark_check=1 stress-33431 [001] ..... 13223.619150: reclaim_retry_zone: node=0 zone=Normal order=0 reclaimable=4260 available=1772019 min_wmark=5962 no_progress_loops=6 wmark_check=1 stress-33431 [001] ..... 13223.619510: reclaim_retry_zone: node=0 zone=Normal order=0 reclaimable=4260 available=1772019 min_wmark=5962 no_progress_loops=7 wmark_check=1 stress-33431 [001] ..... 13223.619850: reclaim_retry_zone: node=0 zone=Normal order=0 reclaimable=4260 available=1772019 min_wmark=5962 no_progress_loops=8 wmark_check=1 stress-33431 [001] ..... 13223.620171: reclaim_retry_zone: node=0 zone=Normal order=0 reclaimable=4260 available=1772019 min_wmark=5962 no_progress_loops=9 wmark_check=1 stress-33431 [001] ..... 13223.620533: reclaim_retry_zone: node=0 zone=Normal order=0 reclaimable=4260 available=1772019 min_wmark=5962 no_progress_loops=10 wmark_check=1 stress-33431 [001] ..... 13223.620894: reclaim_retry_zone: node=0 zone=Normal order=0 reclaimable=4260 available=1772019 min_wmark=5962 no_progress_loops=11 wmark_check=1 stress-33431 [001] ..... 13223.621224: reclaim_retry_zone: node=0 zone=Normal order=0 reclaimable=4260 available=1772019 min_wmark=5962 no_progress_loops=12 wmark_check=1 stress-33431 [001] ..... 13223.621551: reclaim_retry_zone: node=0 zone=Normal order=0 reclaimable=4260 available=1772019 min_wmark=5962 no_progress_loops=13 wmark_check=1 stress-33431 [001] ..... 13223.621847: reclaim_retry_zone: node=0 zone=Normal order=0 reclaimable=4260 available=1772019 min_wmark=5962 no_progress_loops=14 wmark_check=1 stress-33431 [001] ..... 13223.622200: reclaim_retry_zone: node=0 zone=Normal order=0 reclaimable=4260 available=1772019 min_wmark=5962 no_progress_loops=15 wmark_check=1 stress-33431 [001] ..... 13223.622580: reclaim_retry_zone: node=0 zone=Normal order=0 reclaimable=4260 available=1772019 min_wmark=5962 no_progress_loops=16 wmark_check=1 With this patch, we can check the right node and get less retry in __alloc_pages_slowpath() because there is nothing to do. Link: https://lkml.kernel.org/r/20240822092612.3209286-1-hezhongkun.hzk@bytedance.com Signed-off-by: Zhongkun He Suggested-by: Michal Hocko Acked-by: Michal Hocko Cc: Johannes Weiner Cc: Mel Gorman Cc: Zefan Li Signed-off-by: Andrew Morton --- mm/compaction.c | 6 ++++++ mm/page_alloc.c | 5 +++++ 2 files changed, 11 insertions(+) diff --git a/mm/compaction.c b/mm/compaction.c index d1041fbce679..a2b16b08cbbf 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -23,6 +23,7 @@ #include #include #include +#include #include "internal.h" #ifdef CONFIG_COMPACTION @@ -2822,6 +2823,11 @@ enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order, ac->highest_zoneidx, ac->nodemask) { enum compact_result status; + if (cpusets_enabled() && + (alloc_flags & ALLOC_CPUSET) && + !__cpuset_zone_allowed(zone, gfp_mask)) + continue; + if (prio > MIN_COMPACT_PRIORITY && compaction_deferred(zone, order)) { rc = max_t(enum compact_result, COMPACT_DEFERRED, rc); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index da603080214c..6dd0b409e3c2 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -4092,6 +4092,11 @@ should_reclaim_retry(gfp_t gfp_mask, unsigned order, unsigned long min_wmark = min_wmark_pages(zone); bool wmark; + if (cpusets_enabled() && + (alloc_flags & ALLOC_CPUSET) && + !__cpuset_zone_allowed(zone, gfp_mask)) + continue; + available = reclaimable = zone_reclaimable_pages(zone); available += zone_page_state_snapshot(zone, NR_FREE_PAGES);