On Wed, May 3, 2023 at 1:50 AM Michal Hocko <mhocko@xxxxxxxx> wrote:
>
> On Fri 28-04-23 13:24:06, Yosry Ahmed wrote:
> > Commit c8713d0b2312 ("mm: memcontrol: dump memory.stat during cgroup
> > OOM") made sure we dump all the stats in memory.stat during a cgroup
> > OOM, but it also introduced a slight behavioral change. The code used to
> > print the non-hierarchical v1 cgroup stats for the entire cgroup
> > subtree, now it only prints the v2 cgroup stats for the cgroup under
> > OOM.
> >
> > For cgroup v1 users, this introduces a few problems:
> > (a) The non-hierarchical stats of the memcg under OOM are no longer
> > shown.
> > (b) A couple of v1-only stats (e.g. pgpgin, pgpgout) are no longer
> > shown.
> > (c) We show the list of cgroup v2 stats, even in cgroup v1. This list of
> > stats is not tracked with v1 in mind. While most of the stats seem to be
> > working on v1, there may be some stats that are not fully or correctly
> > tracked.
> >
> > Although OOM log is not set in stone, we should not change it for no
> > reason. When upgrading the kernel version to a version including
> > commit c8713d0b2312 ("mm: memcontrol: dump memory.stat during cgroup
> > OOM"), these behavioral changes are noticed in cgroup v1.
> >
> > The fix is simple. Commit c8713d0b2312 ("mm: memcontrol: dump memory.stat
> > during cgroup OOM") separated stats formatting from stats display for
> > v2, to reuse the stats formatting in the OOM logs. Do the same for v1.
> >
> > Move the v2 specific formatting from memory_stat_format() to
> > memcg_stat_format(), add memcg1_stat_format() for v1, and make
> > memory_stat_format() select between them based on cgroup version.
> > Since memory_stat_show() now works for both v1 & v2, drop
> > memcg_stat_show().
> >
> > Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
>
> Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> Thanks
Thanks Michal!
>
> > ---
> > mm/memcontrol.c | 60 ++++++++++++++++++++++++++++---------------------
> > 1 file changed, 35 insertions(+), 25 deletions(-)
> >
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index 5922940f92c9..2b492f8d540c 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -1551,7 +1551,7 @@ static inline unsigned long memcg_page_state_output(struct mem_cgroup *memcg,
> > return memcg_page_state(memcg, item) * memcg_page_state_unit(item);
> > }
> >
> > -static void memory_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
> > +static void memcg_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
> > {
> > int i;
> >
> > @@ -1604,6 +1604,17 @@ static void memory_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
> > WARN_ON_ONCE(seq_buf_has_overflowed(s));
> > }
> >
> > +static void memcg1_stat_format(struct mem_cgroup *memcg, struct seq_buf *s);
> > +
> > +static void memory_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
> > +{
> > + if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
> > + memcg_stat_format(memcg, s);
> > + else
> > + memcg1_stat_format(memcg, s);
> > + WARN_ON_ONCE(seq_buf_has_overflowed(s));
> > +}
> > +
> > #define K(x) ((x) << (PAGE_SHIFT-10))
> > /**
> > * mem_cgroup_print_oom_context: Print OOM information relevant to
> > @@ -4078,9 +4089,8 @@ static const unsigned int memcg1_events[] = {
> > PGMAJFAULT,
> > };
> >
> > -static int memcg_stat_show(struct seq_file *m, void *v)
> > +static void memcg1_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
> > {
> > - struct mem_cgroup *memcg = mem_cgroup_from_seq(m);
> > unsigned long memory, memsw;
> > struct mem_cgroup *mi;
> > unsigned int i;
> > @@ -4095,18 +4105,18 @@ static int memcg_stat_show(struct seq_file *m, void *v)
> > if (memcg1_stats[i] == MEMCG_SWAP && !do_memsw_account())
> > continue;
> > nr = memcg_page_state_local(memcg, memcg1_stats[i]);
> > - seq_printf(m, "%s %lu\n", memcg1_stat_names[i],
> > + seq_buf_printf(s, "%s %lu\n", memcg1_stat_names[i],
> > nr * memcg_page_state_unit(memcg1_stats[i]));
> > }
> >
> > for (i = 0; i < ARRAY_SIZE(memcg1_events); i++)
> > - seq_printf(m, "%s %lu\n", vm_event_name(memcg1_events[i]),
> > - memcg_events_local(memcg, memcg1_events[i]));
> > + seq_buf_printf(s, "%s %lu\n", vm_event_name(memcg1_events[i]),
> > + memcg_events_local(memcg, memcg1_events[i]));
> >
> > for (i = 0; i < NR_LRU_LISTS; i++)
> > - seq_printf(m, "%s %lu\n", lru_list_name(i),
> > - memcg_page_state_local(memcg, NR_LRU_BASE + i) *
> > - PAGE_SIZE);
> > + seq_buf_printf(s, "%s %lu\n", lru_list_name(i),
> > + memcg_page_state_local(memcg, NR_LRU_BASE + i) *
> > + PAGE_SIZE);
> >
> > /* Hierarchical information */
> > memory = memsw = PAGE_COUNTER_MAX;
> > @@ -4114,11 +4124,11 @@ static int memcg_stat_show(struct seq_file *m, void *v)
> > memory = min(memory, READ_ONCE(mi->memory.max));
> > memsw = min(memsw, READ_ONCE(mi->memsw.max));
> > }
> > - seq_printf(m, "hierarchical_memory_limit %llu\n",
> > - (u64)memory * PAGE_SIZE);
> > + seq_buf_printf(s, "hierarchical_memory_limit %llu\n",
> > + (u64)memory * PAGE_SIZE);
> > if (do_memsw_account())
> > - seq_printf(m, "hierarchical_memsw_limit %llu\n",
> > - (u64)memsw * PAGE_SIZE);
> > + seq_buf_printf(s, "hierarchical_memsw_limit %llu\n",
> > + (u64)memsw * PAGE_SIZE);
> >
> > for (i = 0; i < ARRAY_SIZE(memcg1_stats); i++) {
> > unsigned long nr;
> > @@ -4126,19 +4136,19 @@ static int memcg_stat_show(struct seq_file *m, void *v)
> > if (memcg1_stats[i] == MEMCG_SWAP && !do_memsw_account())
> > continue;
> > nr = memcg_page_state(memcg, memcg1_stats[i]);
> > - seq_printf(m, "total_%s %llu\n", memcg1_stat_names[i],
> > + seq_buf_printf(s, "total_%s %llu\n", memcg1_stat_names[i],
> > (u64)nr * memcg_page_state_unit(memcg1_stats[i]));
> > }
> >
> > for (i = 0; i < ARRAY_SIZE(memcg1_events); i++)
> > - seq_printf(m, "total_%s %llu\n",
> > - vm_event_name(memcg1_events[i]),
> > - (u64)memcg_events(memcg, memcg1_events[i]));
> > + seq_buf_printf(s, "total_%s %llu\n",
> > + vm_event_name(memcg1_events[i]),
> > + (u64)memcg_events(memcg, memcg1_events[i]));
> >
> > for (i = 0; i < NR_LRU_LISTS; i++)
> > - seq_printf(m, "total_%s %llu\n", lru_list_name(i),
> > - (u64)memcg_page_state(memcg, NR_LRU_BASE + i) *
> > - PAGE_SIZE);
> > + seq_buf_printf(s, "total_%s %llu\n", lru_list_name(i),
> > + (u64)memcg_page_state(memcg, NR_LRU_BASE + i) *
> > + PAGE_SIZE);
> >
> > #ifdef CONFIG_DEBUG_VM
> > {
> > @@ -4153,12 +4163,10 @@ static int memcg_stat_show(struct seq_file *m, void *v)
> > anon_cost += mz->lruvec.anon_cost;
> > file_cost += mz->lruvec.file_cost;
> > }
> > - seq_printf(m, "anon_cost %lu\n", anon_cost);
> > - seq_printf(m, "file_cost %lu\n", file_cost);
> > + seq_buf_printf(s, "anon_cost %lu\n", anon_cost);
> > + seq_buf_printf(s, "file_cost %lu\n", file_cost);
> > }
> > #endif
> > -
> > - return 0;
> > }
> >
> > static u64 mem_cgroup_swappiness_read(struct cgroup_subsys_state *css,
> > @@ -4998,6 +5006,8 @@ static int mem_cgroup_slab_show(struct seq_file *m, void *p)
> > }
> > #endif
> >
> > +static int memory_stat_show(struct seq_file *m, void *v);
> > +
> > static struct cftype mem_cgroup_legacy_files[] = {
> > {
> > .name = "usage_in_bytes",
> > @@ -5030,7 +5040,7 @@ static struct cftype mem_cgroup_legacy_files[] = {
> > },
> > {
> > .name = "stat",
> > - .seq_show = memcg_stat_show,
> > + .seq_show = memory_stat_show,
> > },
> > {
> > .name = "force_empty",
> > --
> > 2.40.1.495.gc816e09b53d-goog
>
> --
> Michal Hocko
> SUSE Labs
