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Message-ID: <ZsbZsf2Z93_d9PQR@tiehlicka> Date: Thu, 22 Aug 2024 08:24:49 +0200 From: Michal Hocko <mhocko@...e.com> To: Zhongkun He <hezhongkun.hzk@...edance.com> Cc: akpm@...ux-foundation.org, mgorman@...hsingularity.net, hannes@...xchg.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org, lizefan.x@...edance.com Subject: Re: [External] Re: [PATCH] mm:page_alloc: fix the NULL ac->nodemask in __alloc_pages_slowpath() On Thu 22-08-24 11:15:34, Zhongkun He wrote: > On Wed, Aug 21, 2024 at 11:00 PM Michal Hocko <mhocko@...e.com> wrote: > > > > On Wed 21-08-24 21:59:00, Zhongkun He wrote: > > > I found a problem in my test machine that should_reclaim_retry() do > > > not get the right node if i set the cpuset.mems > > > > > > 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 > > > > OK, so the test gets killed as expected. > > > > > 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 > > > > Are you suggesting that the problem is that should_reclaim_retry is > > iterating nodes which are not allowed by cpusets and that makes the > > retry loop happening more than unnecessary? > > Yes, exactly. > > > > > Is there any reason why you haven't done the same that the page > > allocator does in this case? > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index 28f80daf5c04..cbf09c0e3b8a 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -4098,6 +4098,11 @@ 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); > > > > That was my original version, but I found that the problem exists in > other places. > Please see the function flow below. > > __alloc_pages_slowpath: > > get_page_from_freelist > __cpuset_zone_allowed /* check the node */ > > __alloc_pages_direct_reclaim > shrink_zones > cpuset_zone_allowed（）/* check the node */ > > __alloc_pages_direct_compact > try_to_compact_pages > /* do not check the cpuset_zone_allowed（）*/ > > should_reclaim_retry > /* do not check the cpuset_zone_allowed（）*/ > > should_compact_retry > compaction_zonelist_suitable > /* do not check the cpuset_zone_allowed（）*/ > > Should we add __cpuset_zone_allowed() checks in the three functions > listed above, > or should we set the nodemask in __alloc_pages_slowpath() if it is empty > and the request comes from user space? cpuset integration into the page allocator is rather complex (check ALLOC_CPUSET) use. Reviewing your change is not an easy task to make sure all the subtlety is preserved. Therefore I would suggest addressing the specific issue you have found. -- Michal Hocko SUSE Labs
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