memcg-add-tracing-for-memcg-stat-updates.patch removed from -mm tree

merged mm-stable Andrew Morton 1 participant 1 message Nov 6, 2024

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Andrew Morton

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2024-11-06 00:59 UTC #0 lore raw

The quilt patch titled
Subject: memcg: add tracing for memcg stat updates
has been removed from the -mm tree. Its filename was
memcg-add-tracing-for-memcg-stat-updates.patch

This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Shakeel Butt <[email protected]>
Subject: memcg: add tracing for memcg stat updates
Date: Wed, 9 Oct 2024 17:35:50 -0700

The memcg stats are maintained in rstat infrastructure which provides very fast updates side and reasonable read side. However memcg added plethora of stats and made the read side, which is cgroup rstat flush, very slow. To solve that, threshold was added in the memcg stats read side i.e. no need to flush the stats if updates are within the threshold.

This threshold based improvement worked for sometime but more stats were added to memcg and also the read codepath was getting triggered in the performance sensitive paths which made threshold based ratelimiting ineffective. We need more visibility into the hot and cold stats i.e. stats with a lot of updates. Let's add trace to get that visibility.

[[email protected]: use unsigned long type for memcg_rstat_events, per Yosry]

Link https://lkml.kernel.org/r/[email protected] open here

Signed-off-by Shakeel Butt <[email protected]>

Acked-by Roman Gushchin <[email protected]>

Reviewed-by Yosry Ahmed <[email protected]>

Acked-by Johannes Weiner <[email protected]>

Reviewed-by T.J. Mercier <[email protected]>

Cc Michal Hocko <[email protected]>

Cc Muchun Song <[email protected]>

Cc JP Kobryn <[email protected]>

Cc Steven Rostedt (Google) <[email protected]>

Signed-off-by Andrew Morton <[email protected]>

---

 include/trace/events/memcg.h |   81 +++++++++++++++++++++++++++++++++
 mm/memcontrol.c              |   13 ++++-
 2 files changed, 92 insertions(+), 2 deletions(-)

include/trace/events/memcg.h new file +81 -0

new file mode 100644
@@ -0,0 +1,81 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM memcg
+
+#if !defined(_TRACE_MEMCG_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_MEMCG_H
+
+#include <linux/memcontrol.h>
+#include <linux/tracepoint.h>
+
+
+DECLARE_EVENT_CLASS(memcg_rstat_stats,
+
+	TP_PROTO(struct mem_cgroup *memcg, int item, int val),
+
+	TP_ARGS(memcg, item, val),
+
+	TP_STRUCT__entry(
+		__field(u64, id)
+		__field(int, item)
+		__field(int, val)
+	),
+
+	TP_fast_assign(
+		__entry->id = cgroup_id(memcg->css.cgroup);
+		__entry->item = item;
+		__entry->val = val;
+	),
+
+	TP_printk("memcg_id=%llu item=%d val=%d",
+		  __entry->id, __entry->item, __entry->val)
+);
+
+DEFINE_EVENT(memcg_rstat_stats, mod_memcg_state,
+
+	TP_PROTO(struct mem_cgroup *memcg, int item, int val),
+
+	TP_ARGS(memcg, item, val)
+);
+
+DEFINE_EVENT(memcg_rstat_stats, mod_memcg_lruvec_state,
+
+	TP_PROTO(struct mem_cgroup *memcg, int item, int val),
+
+	TP_ARGS(memcg, item, val)
+);
+
+DECLARE_EVENT_CLASS(memcg_rstat_events,
+
+	TP_PROTO(struct mem_cgroup *memcg, int item, unsigned long val),
+
+	TP_ARGS(memcg, item, val),
+
+	TP_STRUCT__entry(
+		__field(u64, id)
+		__field(int, item)
+		__field(unsigned long, val)
+	),
+
+	TP_fast_assign(
+		__entry->id = cgroup_id(memcg->css.cgroup);
+		__entry->item = item;
+		__entry->val = val;
+	),
+
+	TP_printk("memcg_id=%llu item=%d val=%lu",
+		  __entry->id, __entry->item, __entry->val)
+);
+
+DEFINE_EVENT(memcg_rstat_events, count_memcg_events,
+
+	TP_PROTO(struct mem_cgroup *memcg, int item, unsigned long val),
+
+	TP_ARGS(memcg, item, val)
+);
+
+
+#endif /* _TRACE_MEMCG_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>

mm/memcontrol.c renamed from mm/memcontrol.c~memcg-add-tracing-for-memcg-stat-updates +11 -2

@@ -71,6 +71,10 @@
 
 #include <linux/uaccess.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/memcg.h>
+#undef CREATE_TRACE_POINTS
+
 #include <trace/events/vmscan.h>
 
 struct cgroup_subsys memory_cgrp_subsys __read_mostly;

@@ -682,7 +686,9 @@ void __mod_memcg_state(struct mem_cgroup
 		return;
 
 	__this_cpu_add(memcg->vmstats_percpu->state[i], val);
-	memcg_rstat_updated(memcg, memcg_state_val_in_pages(idx, val));
+	val = memcg_state_val_in_pages(idx, val);
+	memcg_rstat_updated(memcg, val);
+	trace_mod_memcg_state(memcg, idx, val);
 }
 
 /* idx can be of type enum memcg_stat_item or node_stat_item. */

@@ -741,7 +747,9 @@ static void __mod_memcg_lruvec_state(str
 	/* Update lruvec */
 	__this_cpu_add(pn->lruvec_stats_percpu->state[i], val);
 
-	memcg_rstat_updated(memcg, memcg_state_val_in_pages(idx, val));
+	val = memcg_state_val_in_pages(idx, val);
+	memcg_rstat_updated(memcg, val);
+	trace_mod_memcg_lruvec_state(memcg, idx, val);
 	memcg_stats_unlock();
 }

@@ -832,6 +840,7 @@ void __count_memcg_events(struct mem_cgr
 	memcg_stats_lock();
 	__this_cpu_add(memcg->vmstats_percpu->events[i], count);
 	memcg_rstat_updated(memcg, count);
+	trace_count_memcg_events(memcg, idx, count);
 	memcg_stats_unlock();
 }

Patches currently in -mm which might be from [email protected] are