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SubjectRe: [PATCH] vmscan: do not evict inactive pages when skipping an active list scan
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> In AIM7 runs, recent kernels start swapping out anonymous pages
> well before they should. This is due to shrink_list falling
> through to shrink_inactive_list if !inactive_anon_is_low(zone, sc),
> when all we really wanted to do is pre-age some anonymous pages to
> give them extra time to be referenced while on the inactive list.
>
> The obvious fix is to make sure that shrink_list does not fall
> through to scanning/reclaiming inactive pages when we called it
> to scan one of the active lists.
>
> This change should be safe because the loop in shrink_zone ensures
> that we will still shrink the anon and file inactive lists whenever
> we should.

Good catch!


>
> Reported-by: Larry Woodman <lwoodman@redhat.com>
> Signed-off-by: Rik van Riel <riel@redhat.com>
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 777af57..ec4dfda 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1469,13 +1469,15 @@ static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
> {
> int file = is_file_lru(lru);
>
> - if (lru == LRU_ACTIVE_FILE && inactive_file_is_low(zone, sc)) {
> - shrink_active_list(nr_to_scan, zone, sc, priority, file);
> + if (lru == LRU_ACTIVE_FILE) {
> + if (inactive_file_is_low(zone, sc))
> + shrink_active_list(nr_to_scan, zone, sc, priority, file);
> return 0;
> }
>
> - if (lru == LRU_ACTIVE_ANON && inactive_anon_is_low(zone, sc)) {
> - shrink_active_list(nr_to_scan, zone, sc, priority, file);
> + if (lru == LRU_ACTIVE_ANON) {
> + if (inactive_file_is_low(zone, sc))

This inactive_file_is_low() should be inactive_anon_is_low().
cut-n-paste programming often makes similar mistake. probaby we need make
more cleanup to this function.

How about this? (this is incremental patch from you)


Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
---
mm/vmscan.c | 17 ++++++++++-------
1 files changed, 10 insertions(+), 7 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index a8f61c0..80e94a2 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1467,22 +1467,25 @@ static int inactive_file_is_low(struct zone *zone, struct scan_control *sc)
return low;
}

+static int inactive_list_is_low(struct zone *zone, struct scan_control *sc, int file)
+{
+ if (file)
+ return inactive_file_is_low(zone, sc);
+ else
+ return inactive_anon_is_low(zone, sc);
+}
+
static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan,
struct zone *zone, struct scan_control *sc, int priority)
{
int file = is_file_lru(lru);

- if (lru == LRU_ACTIVE_FILE) {
- if (inactive_file_is_low(zone, sc))
+ if (is_active_lru(lru)) {
+ if (inactive_list_is_low(zone, sc, file))
shrink_active_list(nr_to_scan, zone, sc, priority, file);
return 0;
}

- if (lru == LRU_ACTIVE_ANON) {
- if (inactive_file_is_low(zone, sc))
- shrink_active_list(nr_to_scan, zone, sc, priority, file);
- return 0;
- }
return shrink_inactive_list(nr_to_scan, zone, sc, priority, file);
}

--
1.6.5.2







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