mm: memcg: only evict file pages when we have plenty

mm: memcg: only evict file pages when we have plenty

e986850 ("mm, vmscan: only evict file pages when we have plenty") makes a
point of not going for anonymous memory while there is still enough
inactive cache around.

The check was added only for global reclaim, but it is just as useful to
reduce swapping in memory cgroup reclaim:

200M-memcg-defconfig-j2

                                 vanilla                   patched
Real time              454.06 (  +0.00%)         453.71 (  -0.08%)
User time              668.57 (  +0.00%)         668.73 (  +0.02%)
System time            128.92 (  +0.00%)         129.53 (  +0.46%)
Swap in               1246.80 (  +0.00%)         814.40 ( -34.65%)
Swap out              1198.90 (  +0.00%)         827.00 ( -30.99%)
Pages allocated   16431288.10 (  +0.00%)    16434035.30 (  +0.02%)
Major faults           681.50 (  +0.00%)         593.70 ( -12.86%)
THP faults             237.20 (  +0.00%)         242.40 (  +2.18%)
THP collapse           241.20 (  +0.00%)         248.50 (  +3.01%)
THP splits             157.30 (  +0.00%)         161.40 (  +2.59%)

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Satoru Moriya <satoru.moriya@hds.com>
Cc: Simon Jeons <simon.jeons@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>