sched/numa: Use {cpu, pid} to create task groups for shared faults
authorPeter Zijlstra <peterz@infradead.org>
Mon, 7 Oct 2013 10:29:21 +0000 (11:29 +0100)
committerIngo Molnar <mingo@kernel.org>
Wed, 9 Oct 2013 12:47:47 +0000 (14:47 +0200)
commit8c8a743c5087bac9caac8155b8f3b367e75cdd0b
treed5cc5c5f4368cf7d3deb627388c869dbea2e83f2
parent90572890d202527c366aa9489b32404e88a7c020
sched/numa: Use {cpu, pid} to create task groups for shared faults

While parallel applications tend to align their data on the cache
boundary, they tend not to align on the page or THP boundary.
Consequently tasks that partition their data can still "false-share"
pages presenting a problem for optimal NUMA placement.

This patch uses NUMA hinting faults to chain tasks together into
numa_groups. As well as storing the NID a task was running on when
accessing a page a truncated representation of the faulting PID is
stored. If subsequent faults are from different PIDs it is reasonable
to assume that those two tasks share a page and are candidates for
being grouped together. Note that this patch makes no scheduling
decisions based on the grouping information.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1381141781-10992-44-git-send-email-mgorman@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
include/linux/mm.h
include/linux/sched.h
kernel/sched/core.c
kernel/sched/fair.c
kernel/sched/sched.h
mm/memory.c