[PATCH 04/10] mm, page_alloc: Remove unnecessary taking of a seqlock when cpusets are disabled

From: Mel Gorman
Date: Wed Aug 12 2015 - 06:48:38 EST


There is a seqcounter that protects against spurious allocation failures
when a task is changing the allowed nodes in a cpuset. There is no need
to check the seqcounter until a cpuset exists.

Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
---
include/linux/cpuset.h | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index 1b357997cac5..6eb27cb480b7 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -104,6 +104,9 @@ extern void cpuset_print_task_mems_allowed(struct task_struct *p);
*/
static inline unsigned int read_mems_allowed_begin(void)
{
+ if (!cpusets_enabled())
+ return 0;
+
return read_seqcount_begin(&current->mems_allowed_seq);
}

@@ -115,6 +118,9 @@ static inline unsigned int read_mems_allowed_begin(void)
*/
static inline bool read_mems_allowed_retry(unsigned int seq)
{
+ if (!cpusets_enabled())
+ return false;
+
return read_seqcount_retry(&current->mems_allowed_seq, seq);
}

--
2.4.6

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