+ mm-shrinker-add-new-event-to-trace-shrink-count.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: shrinker: add new event to trace shrink count
has been added to the -mm mm-unstable branch.  Its filename is
     mm-shrinker-add-new-event-to-trace-shrink-count.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-shrinker-add-new-event-to-trace-shrink-count.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: Bixuan Cui <cuibixuan@vivo.com>
Subject: mm: shrinker: add new event to trace shrink count
Date: Mon, 11 Dec 2023 19:26:39 -0800

Patch series "Make memory reclamation measurable".

When the system memory is low, kswapd reclaims the memory. The key steps
of memory reclamation include
1.shrink_lruvec
  * shrink_active_list, moves folios from the active LRU to the inactive LRU
  * shrink_inactive_list, shrink lru from inactive LRU list
2.shrink_slab
  * shrinker->count_objects(), calculates the freeable memory
  * shrinker->scan_objects(), reclaims the slab memory

The existing tracers in the vmscan are as follows:

--do_try_to_free_pages
--shrink_zones
--trace_mm_vmscan_node_reclaim_begin (tracer)
--shrink_node
--shrink_node_memcgs
  --trace_mm_vmscan_memcg_shrink_begin (tracer)
  --shrink_lruvec
    --shrink_list
      --shrink_active_list
	  --trace_mm_vmscan_lru_shrink_active (tracer)
      --shrink_inactive_list
	  --trace_mm_vmscan_lru_shrink_inactive (tracer)
    --shrink_active_list
  --shrink_slab
    --do_shrink_slab
    --shrinker->count_objects()
    --trace_mm_shrink_slab_start (tracer)
    --shrinker->scan_objects()
    --trace_mm_shrink_slab_end (tracer)
  --trace_mm_vmscan_memcg_shrink_end (tracer)
--trace_mm_vmscan_node_reclaim_end (tracer)

If we get the duration and quantity of shrink lru and slab,
then we can measure the memory recycling, as follows

Measuring memory reclamation with bpf:
  LRU FILE:
	CPU COMM 	ShrinkActive(us) ShrinkInactive(us)  Reclaim(page)
	7   kswapd0	 	26		51		32
	7   kswapd0		52		47		13
  SLAB:
	CPU COMM 		OBJ_NAME		Count_Dur(us) Freeable(page) Scan_Dur(us) Reclaim(page)
	 1  kswapd0		super_cache_scan.cfi_jt     2		    341		   3225		128
	 7  kswapd0		super_cache_scan.cfi_jt     0		    2247	   8524		1024
	 7  kswapd0	        super_cache_scan.cfi_jt     2367	    0		   0		0

For this, add the new tracer to shrink_active_list/shrink_inactive_list
and shrinker->count_objects().


This patch (of 2):

do_shrink_slab() calculates the freeable memory through
shrinker->count_objects(), and then reclaims the memory through
shrinker->scan_objects().  When reclaiming memory,
shrinker->count_objects() takes a certain amount of time:

	Fun               spend(us)
	ext4_es_count     4302
	ext4_es_scan      12
	super_cache_count 4195
	super_cache_scan  2103

Therefore, adding the trace event to count_objects() can more accurately
obtain the time taken for slab memory recycling.

Example of output:
         kswapd0-103     [003] .....  1098.317942: mm_shrink_count_start: kfree_rcu_shrink_count.cfi_jt+0x0/0x8 00000000c540ff51: nid: 0
         kswapd0-103     [003] .....  1098.317951: mm_shrink_count_end: kfree_rcu_shrink_count.cfi_jt+0x0/0x8 00000000c540ff51: nid: 0 freeable:36

Link: https://lkml.kernel.org/r/20231212032640.6968-2-cuibixuan@vivo.com
Signed-off-by: Bixuan Cui <cuibixuan@vivo.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/trace/events/vmscan.h |   49 ++++++++++++++++++++++++++++++++
 mm/shrinker.c                 |    4 ++
 2 files changed, 53 insertions(+)

--- a/include/trace/events/vmscan.h~mm-shrinker-add-new-event-to-trace-shrink-count
+++ a/include/trace/events/vmscan.h
@@ -196,6 +196,55 @@ DEFINE_EVENT(mm_vmscan_direct_reclaim_en
 );
 #endif /* CONFIG_MEMCG */
 
+TRACE_EVENT(mm_shrink_count_start,
+	TP_PROTO(struct shrinker *shr, struct shrink_control *sc),
+
+	TP_ARGS(shr, sc),
+
+	TP_STRUCT__entry(
+		__field(struct shrinker *, shr)
+		__field(void *, shrink)
+		__field(int, nid)
+	),
+
+	TP_fast_assign(
+		__entry->shr = shr;
+		__entry->shrink = shr->count_objects;
+		__entry->nid = sc->nid;
+	),
+
+	TP_printk("%pS %p: nid: %d",
+		__entry->shrink,
+		__entry->shr,
+		__entry->nid)
+);
+
+TRACE_EVENT(mm_shrink_count_end,
+	TP_PROTO(struct shrinker *shr, struct shrink_control *sc, long freeable),
+
+	TP_ARGS(shr, sc, freeable),
+
+	TP_STRUCT__entry(
+		__field(struct shrinker *, shr)
+		__field(void *, shrink)
+		__field(int, nid)
+		__field(long, freeable)
+	),
+
+	TP_fast_assign(
+		__entry->shr = shr;
+		__entry->shrink = shr->count_objects;
+		__entry->nid = sc->nid;
+		__entry->freeable = freeable;
+	),
+
+	TP_printk("%pS %p: nid: %d freeable:%ld",
+		__entry->shrink,
+		__entry->shr,
+		__entry->nid,
+		__entry->freeable)
+);
+
 TRACE_EVENT(mm_shrink_slab_start,
 	TP_PROTO(struct shrinker *shr, struct shrink_control *sc,
 		long nr_objects_to_shrink, unsigned long cache_items,
--- a/mm/shrinker.c~mm-shrinker-add-new-event-to-trace-shrink-count
+++ a/mm/shrinker.c
@@ -379,7 +379,11 @@ static unsigned long do_shrink_slab(stru
 					  : SHRINK_BATCH;
 	long scanned = 0, next_deferred;
 
+	trace_mm_shrink_count_start(shrinker, shrinkctl);
+
 	freeable = shrinker->count_objects(shrinker, shrinkctl);
+
+	trace_mm_shrink_count_end(shrinker, shrinkctl, freeable);
 	if (freeable == 0 || freeable == SHRINK_EMPTY)
 		return freeable;
 
_

Patches currently in -mm which might be from cuibixuan@vivo.com are

mm-shrinker-add-new-event-to-trace-shrink-count.patch
mm-vmscan-add-new-event-to-trace-shrink-lru.patch