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 Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Bixuan Cui <cuibixuan@xxxxxxxx> Subject: mm: shrinker: add new event to trace shrink count Date: Tue, 19 Dec 2023 17:21:22 -0800 Patch series "Make memory reclamation measurable", v4. 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 4): 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/20231220012123.2787-1-cuibixuan@xxxxxxxx Link: https://lkml.kernel.org/r/20231220012123.2787-2-cuibixuan@xxxxxxxx Signed-off-by: Bixuan Cui <cuibixuan@xxxxxxxx> Reviewed-by: Steven Rostedt <rostedt@xxxxxxxxxxx> Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx> Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> 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(long, freeable) + __field(int, nid) + ), + + TP_fast_assign( + __entry->shr = shr; + __entry->shrink = shr->count_objects; + __entry->freeable = freeable; + __entry->nid = sc->nid; + ), + + 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