linux-kernel - Re: [patch 9/9] Scheduler profiling

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Message-ID: <20070531223322.GC7217@one.firstfloor.org>
Date:	Fri, 1 Jun 2007 00:33:22 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	Andi Kleen <andi@...stfloor.org>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 9/9] Scheduler profiling - Use conditional calls

> I see your point, but there is a level of control on the branch I would
> lack by doing so: the ability to put the call in either the if or else
> branch. It is an optimization on i386.

What does it optimize exactly?

> Also, I live in the expectation that, someday, the gcc guys will be nice
> enough to add some kind of support for a nop-based jump that would
> require code patching to put a jump instead. If it ever happens, my
> macro could evolve into this for newer compiler versions, which I could
> not do with the if() statement you are proposing.

If that ever happens we couldn't use it anyways because Linux still
has to support old compilers for a long time. And when those are dropped the
code could be updated.

-Andi
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