On Fri, Mar 31, 2023 at 1:08 AM Yosry Ahmed <yosryahmed@xxxxxxxxxx> wrote: ... > diff --git a/mm/vmscan.c b/mm/vmscan.c > index a3e38851b34ac..bf9d8e175e92a 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -533,7 +533,35 @@ EXPORT_SYMBOL(mm_account_reclaimed_pages); > static void flush_reclaim_state(struct scan_control *sc, > struct reclaim_state *rs) > { > - if (rs) { > + /* > + * Currently, reclaim_state->reclaimed includes three types of pages > + * freed outside of vmscan: > + * (1) Slab pages. > + * (2) Clean file pages from pruned inodes. > + * (3) XFS freed buffer pages. > + * > + * For all of these cases, we have no way of finding out whether these > + * pages were related to the memcg under reclaim. For example, a freed > + * slab page could have had only a single object charged to the memcg > + * under reclaim. Also, populated inodes are not on shrinker LRUs > + * anymore except on highmem systems. > + * > + * Instead of over-reporting the reclaimed pages in a memcg reclaim, > + * only count such pages in system-wide reclaim. This prevents > + * unnecessary retries during memcg charging and false positive from > + * proactive reclaim (memory.reclaim). What happens when writing to the root memory.reclaim? > + * > + * For uncommon cases were the freed pages were actually significantly > + * charged to the memcg under reclaim, and we end up under-reporting, it > + * should be fine. The freed pages will be uncharged anyway, even if > + * they are not reported properly, and we will be able to make forward > + * progress in charging (which is usually in a retry loop). > + * > + * We can go one step further, and report the uncharged objcg pages in > + * memcg reclaim, to make reporting more accurate and reduce > + * under-reporting, but it's probably not worth the complexity for now. > + */ > + if (rs && !cgroup_reclaim(sc)) { To answer the question above, global_reclaim() would be preferred.