sched/numa: Skip some page migrations after a shared fault
authorRik van Riel <riel@redhat.com>
Mon, 7 Oct 2013 10:29:39 +0000 (11:29 +0100)
committerIngo Molnar <mingo@kernel.org>
Wed, 9 Oct 2013 12:48:21 +0000 (14:48 +0200)
commitde1c9ce6f07fec0381a39a9d0b379ea35aa1167f
treed96bf1a2b25dfa84d3fe5f6fe00fb780800e3ef3
parent1e3646ffc64b232cb14a5ef01d7b98997c1b73f9
sched/numa: Skip some page migrations after a shared fault

Shared faults can lead to lots of unnecessary page migrations,
slowing down the system, and causing private faults to hit the
per-pgdat migration ratelimit.

This patch adds sysctl numa_balancing_migrate_deferred, which specifies
how many shared page migrations to skip unconditionally, after each page
migration that is skipped because it is a shared fault.

This reduces the number of page migrations back and forth in
shared fault situations. It also gives a strong preference to
the tasks that are already running where most of the memory is,
and to moving the other tasks to near the memory.

Testing this with a much higher scan rate than the default
still seems to result in fewer page migrations than before.

Memory seems to be somewhat better consolidated than previously,
with multi-instance specjbb runs on a 4 node system.

Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1381141781-10992-62-git-send-email-mgorman@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Documentation/sysctl/kernel.txt
include/linux/sched.h
kernel/sched/fair.c
kernel/sysctl.c
mm/mempolicy.c