linux-kernel - Re: [PATCH 0/3] tracepoints: delay argument evaluation

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Message-Id: <20090520091817.8E3EEFC38D@magilla.sf.frob.com>
Date:	Wed, 20 May 2009 02:18:17 -0700 (PDT)
From:	Roland McGrath <roland@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Jason Baron <jbaron@...hat.com>, linux-kernel@...r.kernel.org,
	fweisbec@...il.com, mingo@...e.hu, laijs@...fujitsu.com,
	rostedt@...dmis.org, mathieu.desnoyers@...ymtl.ca,
	jiayingz@...gle.com, mbligh@...gle.com, fche@...hat.com
Subject: Re: [PATCH 0/3] tracepoints: delay argument evaluation

> But I think we should be asking GCC to get fixed. Since inline functions
> don't act like a compiler barrier anyway, they might as well not force
> argument evaluation either.

I quite agree.  I'm all for better compilation.  However, usual practice
in the kernel has been to complain about introducing C code sequences
that add a few instructions when compiled by compilers over 5 years old,
let alone the very latest one.  I think it was the expectation of that
sort of sensitive reaction to the hot-path impact of unused tracepoints
that motivated Jason's attempt at microoptimization.

Thanks,
Roland
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