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Subject[tip:sched/core] sched/numa: Check current-> mm before allocating NUMA faults
Commit-ID:  9ff1d9ff3c2c8ab3feaeb2e8056a07ca293f7bde
Gitweb: http://git.kernel.org/tip/9ff1d9ff3c2c8ab3feaeb2e8056a07ca293f7bde
Author: Mel Gorman <mgorman@suse.de>
AuthorDate: Mon, 7 Oct 2013 11:29:04 +0100
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 9 Oct 2013 12:40:31 +0200

sched/numa: Check current->mm before allocating NUMA faults

task_numa_placement checks current->mm but after buffers for faults
have already been uselessly allocated. Move the check earlier.

[peterz@infradead.org: Identified the problem]

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/1381141781-10992-27-git-send-email-mgorman@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/sched/fair.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 89eeb89..3383079 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -930,8 +930,6 @@ static void task_numa_placement(struct task_struct *p)
int seq, nid, max_nid = -1;
unsigned long max_faults = 0;

- if (!p->mm) /* for example, ksmd faulting in a user's mm */
- return;
seq = ACCESS_ONCE(p->mm->numa_scan_seq);
if (p->numa_scan_seq == seq)
return;
@@ -998,6 +996,10 @@ void task_numa_fault(int last_nid, int node, int pages, bool migrated)
if (!numabalancing_enabled)
return;

+ /* for example, ksmd faulting in a user's mm */
+ if (!p->mm)
+ return;
+
/* For now, do not attempt to detect private/shared accesses */
priv = 1;


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