Messages in this thread | | | Subject | Re: [PATCH 04/10] mm, page_alloc: Remove unnecessary taking of a seqlock when cpusets are disabled | From | Vlastimil Babka <> | Date | Tue, 28 Jul 2015 14:32:09 +0200 |
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On 07/20/2015 10:00 AM, Mel Gorman wrote: > From: Mel Gorman <mgorman@suse.de> > > There is a seqcounter that protects spurious allocation fails when a task > is changing the allowed nodes in a cpuset. There is no need to check the > seqcounter until a cpuset exists.
If cpusets become enabled betwen _begin and _retry, then it will retry due to comparing with 0, but not crash, so it's safe.
> Signed-off-by: Mel Gorman <mgorman@sujse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
> --- > 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(¤t->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(¤t->mems_allowed_seq, seq); > } > >
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