linux-kernel - Re: [PATCH] SLUB use cmpxchg

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Date:	Mon, 27 Aug 2007 18:27:15 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Christoph Lameter <clameter@....com>
Cc:	Peter Zijlstra <peterz@...radead.org>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, mingo@...hat.com
Subject: Re: [PATCH] SLUB use cmpxchg_local

* Christoph Lameter (clameter@....com) wrote:
> On Mon, 27 Aug 2007, Mathieu Desnoyers wrote:
> 
> > > The slow path would require disable preemption and two interrupt disables.
> > If the slow path have to call new_slab, then yes. But it seems that not
> > every slow path must call it, so for the other slow paths, only one
> > interrupt disable would be required.
> 
> If we include new_slab then we get to 3 times:
> 
> 1. In the cmpxchg_local emulation that fails
> 
> 2. For the slow path
> 
> 3. When calling the page allocator.
> 

Hrm, I just want to certify one thing: A lot of code paths seems to go
to the slow path without requiring cmpxchg_local to execute at all. So
is the slow path more likely to be triggered by the (!object),
(!node_match) tests or by these same tests done in the redo after the
initial cmpxchg_local ?

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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