6.6-stable review patch. If anyone has any objections, please let me know.
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From: Shakeel Butt shakeelb@google.com
commit d4a5b369ad6d8aae552752ff438dddde653a72ec upstream.
One of our workloads (Postgres 14 + sysbench OLTP) regressed on newer upstream kernel and on further investigation, it seems like the cause is the always synchronous rstat flush in the count_shadow_nodes() added by the commit f82e6bf9bb9b ("mm: memcg: use rstat for non-hierarchical stats"). On further inspection it seems like we don't really need accurate stats in this function as it was already approximating the amount of appropriate shadow entries to keep for maintaining the refault information. Since there is already 2 sec periodic rstat flush, we don't need exact stats here. Let's ratelimit the rstat flush in this code path.
Link: https://lkml.kernel.org/r/20231228073055.4046430-1-shakeelb@google.com Fixes: f82e6bf9bb9b ("mm: memcg: use rstat for non-hierarchical stats") Signed-off-by: Shakeel Butt shakeelb@google.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Yosry Ahmed yosryahmed@google.com Cc: Yu Zhao yuzhao@google.com Cc: Michal Hocko mhocko@suse.com Cc: Roman Gushchin roman.gushchin@linux.dev Cc: Muchun Song songmuchun@bytedance.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Jesper Dangaard Brouer hawk@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/workingset.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/workingset.c +++ b/mm/workingset.c @@ -664,7 +664,7 @@ static unsigned long count_shadow_nodes( struct lruvec *lruvec; int i;
- mem_cgroup_flush_stats(); + mem_cgroup_flush_stats_ratelimited(); lruvec = mem_cgroup_lruvec(sc->memcg, NODE_DATA(sc->nid)); for (pages = 0, i = 0; i < NR_LRU_LISTS; i++) pages += lruvec_page_state_local(lruvec,