Commit a479b078 authored by Li Zhijian's avatar Li Zhijian Committed by Andrew Morton
Browse files

mm/vmscan: accumulate nr_demoted for accurate demotion statistics 

In shrink_folio_list(), demote_folio_list() can be called 2 times. 
Currently stat->nr_demoted will only store the last nr_demoted( the later
nr_demoted is always zero, the former nr_demoted will get lost), as a
result number of demoted pages is not accurate.

Accumulate the nr_demoted count across multiple calls to
demote_folio_list(), ensuring accurate reporting of demotion statistics.

[lizhijian@fujitsu.com: introduce local nr_demoted to fix nr_reclaimed double counting]
  Link: https://lkml.kernel.org/r/20250111015253.425693-1-lizhijian@fujitsu.com
Link: https://lkml.kernel.org/r/20250110122133.423481-1-lizhijian@fujitsu.com


Fixes: f77f0c75 ("mm,memcg: provide per-cgroup counters for NUMA balancing operations")
Signed-off-by: default avatarLi Zhijian <lizhijian@fujitsu.com>
Acked-by: default avatarKaiyang Zhao <kaiyang2@cs.cmu.edu>
Tested-by: default avatarDonet Tom <donettom@linux.ibm.com>
Reviewed-by: default avatarDonet Tom <donettom@linux.ibm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent f921da2c

mm/vmscan.c

+4 −3
Original line number Diff line number Diff line
@@ -1086,7 +1086,7 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, 
	struct folio_batch free_folios;

	LIST_HEAD(ret_folios);

	LIST_HEAD(demote_folios);

	unsigned int nr_reclaimed = 0;

	unsigned int nr_reclaimed = 0, nr_demoted = 0;

	unsigned int pgactivate = 0;

	bool do_demote_pass;

	struct swap_iocb *plug = NULL;
@@ -1550,8 +1550,9 @@ static unsigned int shrink_folio_list(struct list_head *folio_list, 
	/* 'folio_list' is always empty here */



	/* Migrate folios selected for demotion */

	stat->nr_demoted = demote_folio_list(&demote_folios, pgdat);

	nr_reclaimed += stat->nr_demoted;

	nr_demoted = demote_folio_list(&demote_folios, pgdat);

	nr_reclaimed += nr_demoted;

	stat->nr_demoted += nr_demoted;

	/* Folios that could not be demoted are still in @demote_folios */

	if (!list_empty(&demote_folios)) {

		/* Folios which weren't demoted go back on @folio_list */