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

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Message-Id: <1218593399.7576.428.camel@calx>
Date:	Tue, 12 Aug 2008 21:09:59 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	Eduard - Gabriel Munteanu <eduard.munteanu@...ux360.ro>
Cc:	Pekka Enberg <penberg@...helsinki.fi>,
	Christoph Lameter <cl@...ux-foundation.org>,
	mathieu.desnoyers@...ymtl.ca, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, rdunlap@...otime.net,
	rostedt@...dmis.org, tglx@...utronix.de
Subject: Re: [PATCH 4/5] kmemtrace: SLUB hooks.


On Tue, 2008-08-12 at 18:29 +0300, Eduard - Gabriel Munteanu wrote:
> On Mon, Aug 11, 2008 at 05:22:37PM +0300, Pekka Enberg wrote:
> > On Mon, 2008-08-11 at 09:21 -0500, Christoph Lameter wrote:
> > > Pekka Enberg wrote:
> > > 
> > > > The function call is supposed to go away when we convert kmemtrace to
> > > > use Mathieu's markers but I suppose even then we have a problem with
> > > > inlining?
> > > 
> > > The function calls are overwritten with NOPs? Or how does that work?
> > 
> > I have no idea. Mathieu, Eduard?
> 
> Yes, the code is patched at runtime. But AFAIK markers already provide
> this stuff (called "immediate values"). Mathieu's tracepoints also do
> it. But it's not available on all arches. x86 and x86-64 work as far as
> I remember.

Did we ever see size(1) numbers for kernels with and without this
support? I'm still a bit worried about adding branches to such a popular
inline. Simply multiplying the branch test by the number of locations is
pretty substantial, never mind the unlikely part of the branch.

-- 
Mathematics is the supreme nostalgia of our time.

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