Sometimes we'd like to avoid swapping out anonymous memory
in particular, avoid swapping out pages of important process or
process groups while there is a reasonable amount of pagecache
on RAM so that we can satisfy our customers' requirements.
OTOH, we can control how aggressive the kernel will swap memory pages
with /proc/sys/vm/swappiness for global and
/sys/fs/cgroup/memory/memory.swappiness for each memcg.
But with current reclaim implementation, the kernel may swap out
even if we set swappiness==0 and there is pagecache on RAM.
This patch changes the behavior with swappiness==0. If we set
swappiness==0, the kernel does not swap out completely
(for global reclaim until the amount of free pages and filebacked
pages in a zone has been reduced to something very very small
(nr_free + nr_filebacked < high watermark)).
Any comments are welcome.
Regards,
Satoru Moriya
Signed-off-by: Satoru Moriya <satoru.moriya@xxxxxxx>
---
mm/vmscan.c | 6 +++---
1 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index c52b235..27dc3e8 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1983,10 +1983,10 @@ static void get_scan_count(struct mem_cgroup_zone *mz, struct scan_control *sc,
* proportional to the fraction of recently scanned pages on
* each list that were recently referenced and in active use.
*/
- ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1);
+ ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1);
ap /= reclaim_stat->recent_rotated[0] + 1;
- fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1);
+ fp = file_prio * (reclaim_stat->recent_scanned[1] + 1);
fp /= reclaim_stat->recent_rotated[1] + 1;
spin_unlock_irq(&mz->zone->lru_lock);
@@ -1999,7 +1999,7 @@ out:
unsigned long scan;
scan = zone_nr_lru_pages(mz, lru);
- if (priority || noswap) {
+ if (priority || noswap || !vmscan_swappiness(mz, sc)) {
scan >>= priority;
if (!scan && force_scan)
scan = SWAP_CLUSTER_MAX;
--
1.7.6.4
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