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@xxxxxxxx>
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@xxxxxxxx
Signed-off-by: Bixuan Cui <cuibixuan@xxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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@xxxxxxxx are
mm-shrinker-add-new-event-to-trace-shrink-count.patch
mm-vmscan-add-new-event-to-trace-shrink-lru.patch
