linux-kernel - Re: [PATCH 4/5] kmemtrace: SLUB hooks.

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Message-ID: <20080811182938.GD32207@Krystal>
Date:	Mon, 11 Aug 2008 14:29:38 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	rdunlap@...otime.net, mpm@...enic.com, tglx@...utronix.de
Subject: Re: [PATCH 4/5] kmemtrace: SLUB hooks.

* Christoph Lameter (cl@...ux-foundation.org) wrote:
> Steven Rostedt wrote:
> 
> > The kmemtrace_mark_alloc_node itself is an inline function, which calls 
> > another inline function "trace_mark" which is designed to test a 
> > read_mostly variable, and will do an "unlikely" jmp if the variable is 
> > set (which it is when tracing is enabled), to the actual function call.
> > 
> > There should be no extra function calls when this is configured on but 
> > tracing disabled. We try very hard to keep the speed of the tracer as 
> > close to a non tracing kernel as possible when tracing is disabled.
> 
> Makes sense. But then we have even more code bloat because of the tests that
> are inserted in all call sites of kmalloc.
> 

The long-term goal is to turn the tests into NOPs, but only once we get
gcc support.

Mathieu

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Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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