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From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Christoph Lameter <clameter@sgi.com>, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] Implement slub fastpath with sequence number
Date: Tue, 11 Mar 2008 20:41:09 +1100	[thread overview]
Message-ID: <200803112041.09217.nickpiggin@yahoo.com.au> (raw)
In-Reply-To: <20080311093144.GB30220@Krystal>

On Tuesday 11 March 2008 20:31, Mathieu Desnoyers wrote:
> Here is a new version that works. tested on x86. tweaked the bitmasks
> into unions to remove operations from the critical path, but I tried to
> keep that clean. It applies on vm.git HEAD.
>
> It allows the cmpxchg_local to detect object re-use by keeping a counter in
> the freeoffset MSBs.
>
> Whenever an object is freed in the cpu slab cache, the counter is
> incremented. Whenever the alloc/free slow paths are modifying the offset or
> freebase, the sequence counter is also incremented. It is used to make sure
> we know if freebase has been modified in an interrupt nested over the fast
> path.

Wow. I applaud the effort to micro optimise things ;)

But I hope this doesn't get merged until macro-regressions in SLUB
are verified to be fixed. It's pretty clear that SLUB's problem is
not fastpath performance, so I think this would be premature
optimisation.


  reply	other threads:[~2008-03-11  9:41 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-03-11  9:31 Mathieu Desnoyers
2008-03-11  9:41 ` Nick Piggin [this message]
2008-03-11 14:45   ` Pekka Enberg
2008-03-11 23:13     ` Nick Piggin
2008-03-12  4:14       ` Christoph Lameter
2008-03-11 14:34 ` Peter Zijlstra
2008-03-12  4:15   ` Christoph Lameter
2008-03-12 22:17   ` Mathieu Desnoyers
2008-03-13  1:20     ` Mathieu Desnoyers
2008-03-13  1:35       ` Mathieu Desnoyers

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