On 1/11/25 07:22, Li Zhijian wrote:
In the shrink_folio_list() function, 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.
Fixes: f77f0c751478 ("mm,memcg: provide per-cgroup counters for NUMA balancing operations")
Signed-off-by: Li Zhijian <lizhijian@xxxxxxxxxxx>
---
Cc: Kaiyang Zhao <kaiyang2@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Kaiyang, I removed you ACKED tag for V1, please review again
Andrew, Please drop the v1 from the mm-hotfixs-unstable if V2 is
accepted.
V2:
Introudce a local nr_demoted to fix it's counted 2 times by nr_reclaimed wrongly.
---
mm/vmscan.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9a859b7d18d7..7f0624b98aa8 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1053,7 +1053,7 @@ 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;
@@ -1522,8 +1522,9 @@ 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 */
This patch looks good to me.
I tested this patch with the stat fix [1] I could see the demotion
counts are coming correctly.
pgdemote_kswapd 60517
pgdemote_direct 6737
pgdemote_khugepaged 0
[1]
https://lore.kernel.org/linux-mm/20250109060540.451261-1-donettom@xxxxxxxxxxxxx/
Feel free to add
Tested-by: Donet Tom <donettom@xxxxxxxxxxxxx>
Reviewed-by: Donet Tom <donettom@xxxxxxxxxxxxx>
