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().
Changes:
v6: * Add Reviewed-by from Steven Rostedt.
v5: * Use 'DECLARE_EVENT_CLASS(mm_vmscan_lru_shrink_start_template' to
replace 'RACE_EVENT(mm_vmscan_lru_shrink_inactive/active_start'
* Add the explanation for adding new shrink lru events into 'mm: vmscan: add new event to trace shrink lru'
v4: Add Reviewed-by and Changlog to every patch.
v3: Swap the positions of 'nid' and 'freeable' to prevent the hole in the trace event.
v2: Modify trace_mm_vmscan_lru_shrink_inactive() in evict_folios() at the same time to fix build error.
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 | 80 ++++++++++++++++++++++++++++++++++-
mm/shrinker.c | 4 ++
mm/vmscan.c | 11 +++--
3 files changed, 90 insertions(+), 5 deletions(-)
--
2.17.1
