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sched/numa: Use {cpu, pid} to create task groups for shared faults

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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>
This commit is contained in:
Peter Zijlstra
2013-10-07 11:29:21 +01:00
committed by Ingo Molnar
parent 90572890d2
commit 8c8a743c50
6 changed files with 182 additions and 13 deletions
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3
include/linux/sched.h
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@@ -1347,6 +1347,9 @@ struct task_struct {
u64 node_stamp; /* migration stamp */
struct callback_head numa_work;
struct list_head numa_entry;
struct numa_group *numa_group;
/*
* Exponential decaying average of faults on a per-node basis.
* Scheduling placement decisions are made based on the these counts.