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Message-ID: <1334657569.28150.81.camel@twins>
Subject: Re: A quick view of the performance benchmark for semaphore-like
 and mutex
From: Peter Zijlstra <peterz@infradead.org>
To: "Chen, Dennis (SRDC SW)" <Dennis1.Chen@amd.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        "paulmck@linux.vnet.ibm.com" <paulmck@linux.vnet.ibm.com>,
        Paul Mackerras <paulus@samba.org>,
        Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Date: Tue, 17 Apr 2012 12:12:49 +0200
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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.