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authorMel Gorman <mgorman@suse.de>2013-10-07 11:28:59 +0100
committerIngo Molnar <mingo@kernel.org>2013-10-09 12:40:25 +0200
commit745d61476ddb737aad3495fa6d9a8f8c2ee59f86 (patch)
treeae6ebeefdcee8b5615f21e2f8a960f92fbdd2f71 /kernel/sched/core.c
parent688b7585d16ab57a17aa4422a3b290b3a55fa679 (diff)
downloadblackbird-op-linux-745d61476ddb737aad3495fa6d9a8f8c2ee59f86.tar.gz
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sched/numa: Update NUMA hinting faults once per scan
NUMA hinting fault counts and placement decisions are both recorded in the same array which distorts the samples in an unpredictable fashion. The values linearly accumulate during the scan and then decay creating a sawtooth-like pattern in the per-node counts. It also means that placement decisions are time sensitive. At best it means that it is very difficult to state that the buffer holds a decaying average of past faulting behaviour. At worst, it can confuse the load balancer if it sees one node with an artifically high count due to very recent faulting activity and may create a bouncing effect. This patch adds a second array. numa_faults stores the historical data which is used for placement decisions. numa_faults_buffer holds the fault activity during the current scan window. When the scan completes, numa_faults decays and the values from numa_faults_buffer are copied across. 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> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1381141781-10992-22-git-send-email-mgorman@suse.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched/core.c')
-rw-r--r--kernel/sched/core.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d15cd70f85b5..064a0af44540 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1636,6 +1636,7 @@ static void __sched_fork(struct task_struct *p)
p->numa_preferred_nid = -1;
p->numa_work.next = &p->numa_work;
p->numa_faults = NULL;
+ p->numa_faults_buffer = NULL;
#endif /* CONFIG_NUMA_BALANCING */
}
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