linux-kernel - RE: A quick view of the performance benchmark for semaphore-like and mutex

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Message-ID: <491D6B4EAD0A714894D8AD22F4BDE043B15E04@SCYBEXDAG03.amd.com>
Date:	Tue, 17 Apr 2012 11:52:26 +0000
From:	"Chen, Dennis (SRDC SW)" <Dennis1.Chen@....com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	"paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: RE: A quick view of the performance benchmark for semaphore-like
 and mutex

On Tue, Apr 17, 2012 at 6:12 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Tue, 2012-04-17 at 09:36 +0000, Chen, Dennis (SRDC SW) wrote:
>>
>> Interesting!! Semaphore-like is almost 8s slower than mutex... Also, the Events sycles of perf
>> reported is different
>
> I suspect that if you were to use actual semaphores it would be even
> worse, the semaphore implementation doesn't do lock-stealing nor does it
> have fancy assembly fast paths.
>
> In fact, I don't know why you even bother with sems, they're a
> deprecated serialization primitive that really shouldn't be used
> anymore.

Yes, I am also apt to believe that...Actually I never been bothered by sems in my real life, just 
for fun! I enjoy the data :-)

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