linux-kernel - Re: [PATCH 0/5] branch hint tweaks

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Message-ID: <4B0C2445.2000008@klingt.org>
Date:	Tue, 24 Nov 2009 19:21:57 +0100
From:	Tim Blechmann <tim@...ngt.org>
To:	Brian Gerst <brgerst@...il.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5] branch hint tweaks

> Did you run profiling tests again after making these changes to see if
> they had any effect?  likely() and unlikely() are only hints.  GCC
> doesn't have to follow them, or it could be broken in recent GCC
> versions.

i know, the compiler doesn't have to follow the hint ... but with the
likely/unlikely profiling, not the execution time is profiled, but
whether the branch hint is pointing to the right direction on my machine
... if the assembly is actually affected does probably depend on the
compiler version, instruction set, cpu tuning ...

tim

-- 
tim@...ngt.org
http://tim.klingt.org

The aim of education is the knowledge, not of facts, but of values
  William S. Burroughs

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