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

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Message-ID: <1334657569.28150.81.camel@twins>
Date:	Tue, 17 Apr 2012 12:12:49 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Chen, Dennis (SRDC SW)" <Dennis1.Chen@....com>
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, 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.
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