On Sat 12-03-22 07:16:23, Wei Yang wrote: > When memory reclaim failed for a maximum number of attempts and we bail > out of the reclaim loop, we forgot to put the target mem_cgroup chosen > for next reclaim back to the soft limit tree. This prevented pages in > the mem_cgroup from being reclaimed in the future even though the > mem_cgroup exceeded its soft limit. > > Let's say there are two mem_cgroup and both of them exceed the soft > limit, while the first one is more active then the second. Since we add > a mem_cgroup to soft limit tree every 1024 event, the second one just > get a rare chance to be put on soft limit tree even it exceeds the > limit. yes, 1024 could be just 4MB of memory or 2GB if all the charged pages are THPs. So the excess can build up considerably. > As time goes on, the first mem_cgroup was kept close to its soft limit > due to reclaim activities, while the memory usage of the second > mem_cgroup keeps growing over the soft limit for a long time due to its > relatively rare occurrence. > > This patch adds next_mz back to prevent this sceanrio. > > Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx> Even though your changelog is different the change itself is identical to https://lore.kernel.org/linux-mm/8d35206601ccf0e1fe021d24405b2a0c2f4e052f.1613584277.git.tim.c.chen@xxxxxxxxxxxxxxx/ In those cases I would preserve the the original authorship by From: Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx> and add his s-o-b before yours. Acked-by: Michal Hocko <mhocko@xxxxxxxx> Thanks! > --- > mm/memcontrol.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 344a7e891bc5..e803ff02aae2 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -3493,8 +3493,13 @@ unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order, > loop > MEM_CGROUP_MAX_SOFT_LIMIT_RECLAIM_LOOPS)) > break; > } while (!nr_reclaimed); > - if (next_mz) > + if (next_mz) { > + spin_lock_irq(&mctz->lock); > + excess = soft_limit_excess(next_mz->memcg); > + __mem_cgroup_insert_exceeded(next_mz, mctz, excess); > + spin_unlock_irq(&mctz->lock); > css_put(&next_mz->memcg->css); > + } > return nr_reclaimed; > } > > -- > 2.33.1 -- Michal Hocko SUSE Labs
