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mm/vmscan: accumulate nr_demoted for accurate demotion statistics

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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: f77f0c7514 ("mm,memcg: provide per-cgroup counters for NUMA balancing operations")
Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
Acked-by: Kaiyang Zhao <kaiyang2@cs.cmu.edu>
Tested-by: Donet Tom <donettom@linux.ibm.com>
Reviewed-by: Donet Tom <donettom@linux.ibm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Li Zhijian 2025-01-10 20:21:32 +08:00 • committed by Andrew Morton
parent f921da2c34
commit a479b078fd
1 changed files with 4 additions and 3 deletions
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7
mm/vmscan.c
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@ -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 @@ keep:
/* '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 */