The patch titled
Subject: memcg: add flush tracepoint
has been added to the -mm mm-unstable branch. Its filename is
memcg-add-flush-tracepoint.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/memcg-add-flush-tracepoint.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: JP Kobryn <inwardvessel@xxxxxxxxx>
Subject: memcg: add flush tracepoint
Date: Mon, 28 Oct 2024 19:11:06 -0700
This tracepoint gives visibility on how often the flushing of memcg stats
occurs and contains info on whether it was forced, skipped, and the value
of stats updated. It can help with understanding how readers are affected
by having to perform the flush, and the effectiveness of the flush by
inspecting the number of stats updated. Paired with the recently added
tracepoints for tracing rstat updates, it can also help show correlation
where stats exceed thresholds frequently.
Link: https://lkml.kernel.org/r/20241029021106.25587-3-inwardvessel@xxxxxxxxx
Signed-off-by: JP Kobryn <inwardvessel@xxxxxxxxx>
Reviewed-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Shakeel Butt <shakeel.butt@xxxxxxxxx>
Cc: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/trace/events/memcg.h | 25 +++++++++++++++++++++++++
mm/memcontrol.c | 7 ++++++-
2 files changed, 31 insertions(+), 1 deletion(-)
--- a/include/trace/events/memcg.h~memcg-add-flush-tracepoint
+++ a/include/trace/events/memcg.h
@@ -74,6 +74,31 @@ DEFINE_EVENT(memcg_rstat_events, count_m
TP_ARGS(memcg, item, val)
);
+TRACE_EVENT(memcg_flush_stats,
+
+ TP_PROTO(struct mem_cgroup *memcg, s64 stats_updates,
+ bool force, bool needs_flush),
+
+ TP_ARGS(memcg, stats_updates, force, needs_flush),
+
+ TP_STRUCT__entry(
+ __field(u64, id)
+ __field(s64, stats_updates)
+ __field(bool, force)
+ __field(bool, needs_flush)
+ ),
+
+ TP_fast_assign(
+ __entry->id = cgroup_id(memcg->css.cgroup);
+ __entry->stats_updates = stats_updates;
+ __entry->force = force;
+ __entry->needs_flush = needs_flush;
+ ),
+
+ TP_printk("memcg_id=%llu stats_updates=%lld force=%d needs_flush=%d",
+ __entry->id, __entry->stats_updates,
+ __entry->force, __entry->needs_flush)
+);
#endif /* _TRACE_MEMCG_H */
--- a/mm/memcontrol.c~memcg-add-flush-tracepoint
+++ a/mm/memcontrol.c
@@ -596,7 +596,12 @@ static inline void memcg_rstat_updated(s
static void __mem_cgroup_flush_stats(struct mem_cgroup *memcg, bool force)
{
- if (!force && !memcg_vmstats_needs_flush(memcg->vmstats))
+ bool needs_flush = memcg_vmstats_needs_flush(memcg->vmstats);
+
+ trace_memcg_flush_stats(memcg, atomic64_read(&memcg->vmstats->stats_updates),
+ force, needs_flush);
+
+ if (!force && !needs_flush)
return;
if (mem_cgroup_is_root(memcg))
_
Patches currently in -mm which might be from inwardvessel@xxxxxxxxx are
memcg-rename-do_flush_stats-and-add-force-flag.patch
memcg-add-flush-tracepoint.patch
