| From | Greg Kroah-Hartman <> | Subject | [ 203/218] mm: avoid swapping out with swappiness==0 | Date | Fri, 28 Sep 2012 13:17:00 -0700 |
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3.4-stable review patch. If anyone has any objections, please let me know.
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From: Satoru Moriya <satoru.moriya@hds.com>
commit fe35004fbf9eaf67482b074a2e032abb9c89b1dd upstream.
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 in 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)).
Signed-off-by: Satoru Moriya <satoru.moriya@hds.com> Acked-by: Minchan Kim <minchan@kernel.org> Reviewed-by: Rik van Riel <riel@redhat.com> Acked-by: Jerome Marchand <jmarchan@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- mm/vmscan.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1983,10 +1983,10 @@ static void get_scan_count(struct mem_cg * 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;
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