From f77f0c7514789577125c1b2df145703161736359 Mon Sep 17 00:00:00 2001 From: Kaiyang Zhao Date: Wed, 14 Aug 2024 17:42:27 +0000 Subject: mm,memcg: provide per-cgroup counters for NUMA balancing operations The ability to observe the demotion and promotion decisions made by the kernel on a per-cgroup basis is important for monitoring and tuning containerized workloads on machines equipped with tiered memory. Different containers in the system may experience drastically different memory tiering actions that cannot be distinguished from the global counters alone. For example, a container running a workload that has a much hotter memory accesses will likely see more promotions and fewer demotions, potentially depriving a colocated container of top tier memory to such an extent that its performance degrades unacceptably. For another example, some containers may exhibit longer periods between data reuse, causing much more numa_hint_faults than numa_pages_migrated. In this case, tuning hot_threshold_ms may be appropriate, but the signal can easily be lost if only global counters are available. In the long term, we hope to introduce per-cgroup control of promotion and demotion actions to implement memory placement policies in tiering. This patch set adds seven counters to memory.stat in a cgroup: numa_pages_migrated, numa_pte_updates, numa_hint_faults, pgdemote_kswapd, pgdemote_khugepaged, pgdemote_direct and pgpromote_success. pgdemote_* and pgpromote_success are also available in memory.numa_stat. count_memcg_events_mm() is added to count multiple event occurrences at once, and get_mem_cgroup_from_folio() is added because we need to get a reference to the memcg of a folio before it's migrated to track numa_pages_migrated. The accounting of PGDEMOTE_* is moved to shrink_inactive_list() before being changed to per-cgroup. [kaiyang2@cs.cmu.edu: add documentation of the memcg counters in cgroup-v2.rst] Link: https://lkml.kernel.org/r/20240814235122.252309-1-kaiyang2@cs.cmu.edu Link: https://lkml.kernel.org/r/20240814174227.30639-1-kaiyang2@cs.cmu.edu Signed-off-by: Kaiyang Zhao Cc: David Rientjes Cc: Johannes Weiner Cc: Michal Hocko Cc: Muchun Song Cc: Roman Gushchin Cc: Shakeel Butt Cc: Wei Xu Signed-off-by: Andrew Morton --- mm/vmscan.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'mm/vmscan.c') diff --git a/mm/vmscan.c b/mm/vmscan.c index 1b6542aaf81e..1b1fad0c1e11 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1016,9 +1016,6 @@ static unsigned int demote_folio_list(struct list_head *demote_folios, (unsigned long)&mtc, MIGRATE_ASYNC, MR_DEMOTION, &nr_succeeded); - mod_node_page_state(pgdat, PGDEMOTE_KSWAPD + reclaimer_offset(), - nr_succeeded); - return nr_succeeded; } @@ -1516,7 +1513,8 @@ keep: /* 'folio_list' is always empty here */ /* Migrate folios selected for demotion */ - nr_reclaimed += demote_folio_list(&demote_folios, pgdat); + stat->nr_demoted = demote_folio_list(&demote_folios, pgdat); + nr_reclaimed += stat->nr_demoted; /* Folios that could not be demoted are still in @demote_folios */ if (!list_empty(&demote_folios)) { /* Folios which weren't demoted go back on @folio_list */ @@ -1982,6 +1980,8 @@ static unsigned long shrink_inactive_list(unsigned long nr_to_scan, spin_lock_irq(&lruvec->lru_lock); move_folios_to_lru(lruvec, &folio_list); + __mod_lruvec_state(lruvec, PGDEMOTE_KSWAPD + reclaimer_offset(), + stat.nr_demoted); __mod_node_page_state(pgdat, NR_ISOLATED_ANON + file, -nr_taken); item = PGSTEAL_KSWAPD + reclaimer_offset(); if (!cgroup_reclaim(sc)) -- cgit v1.2.3