lkml.org 
[lkml]   [2014]   [Mar]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] mm: Only force scan in reclaim when none of the LRUs are big enough.
On 03/15/2014 11:36 PM, Hugh Dickins wrote:
> From: Suleiman Souhlal <suleiman@google.com>
>
> Prior to this change, we would decide whether to force scan a LRU
> during reclaim if that LRU itself was too small for the current
> priority. However, this can lead to the file LRU getting force
> scanned even if there are a lot of anonymous pages we can reclaim,
> leading to hot file pages getting needlessly reclaimed.
>
> To address this, we instead only force scan when none of the
> reclaimable LRUs are big enough.
>
> Gives huge improvements with zswap. For example, when doing -j20
> kernel build in a 500MB container with zswap enabled, runtime (in
> seconds) is greatly reduced:
>
> x without this change
> + with this change
> N Min Max Median Avg Stddev
> x 5 700.997 790.076 763.928 754.05 39.59493
> + 5 141.634 197.899 155.706 161.9 21.270224
> Difference at 95.0% confidence
> -592.15 +/- 46.3521
> -78.5293% +/- 6.14709%
> (Student's t, pooled s = 31.7819)
>
> Should also give some improvements in regular (non-zswap) swap cases.
>
> Yes, hughd found significant speedup using regular swap, with several
> memcgs under pressure; and it should also be effective in the non-memcg
> case, whenever one or another zone LRU is forced too small.
>
> Signed-off-by: Suleiman Souhlal <suleiman@google.com>
> Signed-off-by: Hugh Dickins <hughd@google.com>

Acked-by: Rik van Riel <riel@redhat.com>



\
 
 \ /
  Last update: 2014-03-27 22:21    [W:0.042 / U:2.012 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site