linux-kernel - Re: [patch 00/10] [RFC] SLUB patches for more functionality, performance and maintenance

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Date:	Tue, 10 Jul 2007 11:38:02 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
cc:	Martin Bligh <mbligh@...igh.org>, Andi Kleen <andi@...stfloor.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	David Miller <davem@...emloft.net>
Subject: Re: [patch 00/10] [RFC] SLUB patches for more functionality,
 performance and maintenance

On Tue, 10 Jul 2007, Mathieu Desnoyers wrote:

> cmpxchg_local is not available on all archs, but local_cmpxchg is. It
> expects a local_t type which is nothing else than a long. When the local
> atomic operation is not more efficient or not implemented on a given
> architecture, asm-generic/local.h falls back on atomic_long_t. If you
> want, you could work on the local_t type, which you could cast from a
> long to a pointer when you need so, since their size are, AFAIK, always
> the same (and some VM code even assume this is always the case).

It would be cleaner to have cmpxchg_local on all arches. The type 
conversion is hacky. If this is really working then we should also use the 
mechanism for other things like the vm statistics.

> The measurements I get (in cycles):
> 
>              enable interrupts (STI)   disable interrupts (CLI)   local CMPXCHG
> IA32 (P4)    112                        82                         26
> x86_64 AMD64 125                       102                         19

Looks good and seems to indicate that we can at least double the speed of 
slab allocation.
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