Messages in this thread | | | Subject | Re: WARNINGs in set_task_reclaim_state with memory cgroup and full memory usage | From | Yang Shi <> | Date | Tue, 27 Aug 2019 10:12:07 -0700 |
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On 8/27/19 3:43 AM, Michal Hocko wrote: > If there are no objection to the patch I will post it as a standalong > one. > > On Mon 26-08-19 12:55:21, Michal Hocko wrote: >> From 59d128214a62bf2d83c2a2a9cde887b4817275e7 Mon Sep 17 00:00:00 2001 >> From: Michal Hocko <mhocko@suse.com> >> Date: Mon, 26 Aug 2019 12:43:15 +0200 >> Subject: [PATCH] mm, memcg: do not set reclaim_state on soft limit reclaim >> >> Adric Blake has noticed the following warning: >> [38491.963105] WARNING: CPU: 7 PID: 175 at mm/vmscan.c:245 set_task_reclaim_state+0x1e/0x40 >> [...] >> [38491.963239] Call Trace: >> [38491.963246] mem_cgroup_shrink_node+0x9b/0x1d0 >> [38491.963250] mem_cgroup_soft_limit_reclaim+0x10c/0x3a0 >> [38491.963254] balance_pgdat+0x276/0x540 >> [38491.963258] kswapd+0x200/0x3f0 >> [38491.963261] ? wait_woken+0x80/0x80 >> [38491.963265] kthread+0xfd/0x130 >> [38491.963267] ? balance_pgdat+0x540/0x540 >> [38491.963269] ? kthread_park+0x80/0x80 >> [38491.963273] ret_from_fork+0x35/0x40 >> [38491.963276] ---[ end trace 727343df67b2398a ]--- >> >> which tells us that soft limit reclaim is about to overwrite the >> reclaim_state configured up in the call chain (kswapd in this case but >> the direct reclaim is equally possible). This means that reclaim stats >> would get misleading once the soft reclaim returns and another reclaim >> is done. >> >> Fix the warning by dropping set_task_reclaim_state from the soft reclaim >> which is always called with reclaim_state set up.
This is exactly what I thought. Looks good to me. Acked-by: Yang Shi <yang.shi@linux.alibaba.com>
>> >> Reported-by: Adric Blake <promarbler14@gmail.com> >> Signed-off-by: Michal Hocko <mhocko@suse.com> >> --- >> mm/vmscan.c | 5 +++-- >> 1 file changed, 3 insertions(+), 2 deletions(-) >> >> diff --git a/mm/vmscan.c b/mm/vmscan.c >> index c77d1e3761a7..a6c5d0b28321 100644 >> --- a/mm/vmscan.c >> +++ b/mm/vmscan.c >> @@ -3220,6 +3220,7 @@ unsigned long try_to_free_pages(struct zonelist *zonelist, int order, >> >> #ifdef CONFIG_MEMCG >> >> +/* Only used by soft limit reclaim. Do not reuse for anything else. */ >> unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg, >> gfp_t gfp_mask, bool noswap, >> pg_data_t *pgdat, >> @@ -3235,7 +3236,8 @@ unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg, >> }; >> unsigned long lru_pages; >> >> - set_task_reclaim_state(current, &sc.reclaim_state); >> + WARN_ON_ONCE(!current->reclaim_state); >> + >> sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | >> (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); >> >> @@ -3253,7 +3255,6 @@ unsigned long mem_cgroup_shrink_node(struct mem_cgroup *memcg, >> >> trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); >> >> - set_task_reclaim_state(current, NULL); >> *nr_scanned = sc.nr_scanned; >> >> return sc.nr_reclaimed; >> -- >> 2.20.1 >> >> -- >> Michal Hocko >> SUSE Labs
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