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Message-ID: <CACSyD1OdKb4n1SrStdTfhwO0F1eBA5mNruxOeYKrhKP6+jTXAg@mail.gmail.com>
Date: Thu, 22 Aug 2024 11:15:34 +0800
From: Zhongkun He <hezhongkun.hzk@...edance.com>
To: Michal Hocko <mhocko@...e.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 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?
Adding checks respectively in the three functions might be safer and
easier to review.
It would be better if you had any suggestions.
Thanks.
> --
> Michal Hocko
> SUSE Labs
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