[-next,0/2] Make memory reclamation measurable

Message

Bixuan Cui Dec. 12, 2023, 3:26 a.m. UTC

From: cuibixuan <[e-mail]>

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().

cuibixuan (2):
  mm: shrinker: add new event to trace shrink count
  mm: vmscan: add new event to trace shrink lru

 include/trace/events/vmscan.h | 87 ++++++++++++++++++++++++++++++++++-
 mm/shrinker.c                 |  4 ++
 mm/vmscan.c                   |  8 +++-
 3 files changed, 95 insertions(+), 4 deletions(-)