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UPSTREAM: mm: multi-gen LRU: don't spin during memcg release

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When a memcg is in the process of being released mem_cgroup_tryget will
fail because its reference count has already reached 0.  This can happen
during reclaim if the memcg has already been offlined, and we reclaim all
remaining pages attributed to the offlined memcg.  shrink_many attempts to
skip the empty memcg in this case, and continue reclaiming from the
remaining memcgs in the old generation.  If there is only one memcg
remaining, or if all remaining memcgs are in the process of being released
then shrink_many will spin until all memcgs have finished being released.
The release occurs through a workqueue, so it can take a while before
kswapd is able to make any further progress.

This fix results in reductions in kswapd activity and direct reclaim in
a test where 28 apps (working set size > total memory) are repeatedly
launched in a random sequence:

                                       A          B      delta   ratio(%)
           allocstall_movable       5962       3539      -2423     -40.64
            allocstall_normal       2661       2417       -244      -9.17
kswapd_high_wmark_hit_quickly      53152       7594     -45558     -85.71
                   pageoutrun      57365      11750     -45615     -79.52

Bug: 254441685
Link: https://lkml.kernel.org/r/20230814151636.1639123-1-tjmercier@google.com
Fixes: e4dde56cd208 ("mm: multi-gen LRU: per-node lru_gen_folio lists")
Signed-off-by: T.J. Mercier <tjmercier@google.com>
Acked-by: Yu Zhao <yuzhao@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit 6867c7a3320669cbe44b905a3eb35db725c6d470)
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: I37a874d87cf5f2f8fad742f175bc6f603134e660
This commit is contained in:
T.J. Mercier 2023-08-14 15:16:36 +00:00 • committed by Treehugger Robot
parent 3d1b582966
commit e329419f70
1 changed files with 8 additions and 5 deletions
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13
mm/vmscan.c
View file

@ -4804,16 +4804,17 @@ void lru_gen_release_memcg(struct mem_cgroup *memcg)
spin_lock_irq(&pgdat->memcg_lru.lock);
VM_WARN_ON_ONCE(hlist_nulls_unhashed(&lruvec->lrugen.list));
if (hlist_nulls_unhashed(&lruvec->lrugen.list))
goto unlock;
gen = lruvec->lrugen.gen;
hlist_nulls_del_rcu(&lruvec->lrugen.list);
hlist_nulls_del_init_rcu(&lruvec->lrugen.list);
pgdat->memcg_lru.nr_memcgs[gen]--;
if (!pgdat->memcg_lru.nr_memcgs[gen] && gen == get_memcg_gen(pgdat->memcg_lru.seq))
WRITE_ONCE(pgdat->memcg_lru.seq, pgdat->memcg_lru.seq + 1);
unlock:
spin_unlock_irq(&pgdat->memcg_lru.lock);
}
}
@ -5433,8 +5434,10 @@ restart:
rcu_read_lock();
hlist_nulls_for_each_entry_rcu(lrugen, pos, &pgdat->memcg_lru.fifo[gen][bin], list) {
if (op)
if (op) {
lru_gen_rotate_memcg(lruvec, op);
op = 0;
}
mem_cgroup_put(memcg);
@ -5442,7 +5445,7 @@ restart:
memcg = lruvec_memcg(lruvec);
if (!mem_cgroup_tryget(memcg)) {
op = 0;
lru_gen_release_memcg(memcg);
memcg = NULL;
continue;
}