linux-kernel - Re: [PATCH 1/2] tracing/function-return-tracer: Make the function return tracer lockless

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Message-ID: <20081113185515.GA3810@one.firstfloor.org>
Date:	Thu, 13 Nov 2008 19:55:15 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] tracing/function-return-tracer: Make the function return tracer lockless

> Now tell me again how local_* is more efficient than barrier?

Look at the generated assembler, not the source. The M386 check is two instructions
with the i386 stuff just moved away somewhere out of line that is
about never taken. The rest is short and straight forward in asm too.
And a lot of kernels are not compiled with 386 support anyways.

-Andi

-- 
ak@...ux.intel.com
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