From: Christoph Lameter <cl@linux.com>
To: Andi Kleen <andi@firstfloor.org>
Cc: Pekka Enberg <penberg@kernel.org>,
David Miller <davem@davemloft.net>,
marcin.slusarz@gmail.com, mpm@selenic.com,
linux-kernel@vger.kernel.org, rientjes@google.com,
linux-mm@kvack.org
Subject: Re: [PATCH] slub: reduce overhead of slub_debug
Date: Fri, 8 Jul 2011 12:41:24 -0500 (CDT) [thread overview]
Message-ID: <alpine.DEB.2.00.1107081240010.23187@router.home> (raw)
In-Reply-To: <m2box5cplq.fsf@firstfloor.org>
On Thu, 7 Jul 2011, Andi Kleen wrote:
> Christoph Lameter <cl@linux.com> writes:
>
>
> > +#ifdef __HAVE_ARCH_INV_MEMSCAN
> > +void *inv_memscan(void *addr, int c, size_t size)
> > +{
> > + if (!size)
> > + return addr;
> > + asm volatile("repz; scasb\n\t"
>
> This will just do the slow byte accesses again internally.
> scasb is not normally very optimized in microcode as far
> as I know.
>
> Also rep has quite some startup overhead which makes
> it a bad idea for small sizes (<16-20 or so)
>
> I would stay with the C version. I bet that one is
> faster.
If the c code is such an improvement then memscan and other
implementations can be accellerated in the same way. That would be useful
in general. We can get rid of the implementation for memscan and friends
in x86 arch code.
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next prev parent reply other threads:[~2011-07-08 17:41 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-26 19:39 Marcin Slusarz
2011-06-28 19:32 ` Christoph Lameter
2011-06-28 19:40 ` David Daney
2011-06-28 20:58 ` David Rientjes
2011-06-28 21:04 ` Ben Greear
2011-06-28 21:10 ` David Rientjes
2011-06-28 21:16 ` Dave Jones
2011-07-07 18:07 ` Pekka Enberg
2011-07-07 18:17 ` Christoph Lameter
2011-07-07 18:30 ` Ben Greear
2011-07-07 18:42 ` Christoph Lameter
2011-07-07 18:54 ` Ben Greear
2011-07-07 18:30 ` Matt Mackall
2011-07-07 18:52 ` Pekka Enberg
2011-07-07 18:55 ` Matt Mackall
2011-07-07 19:12 ` Christoph Lameter
2011-07-07 19:21 ` David Miller
2011-07-07 19:49 ` Pekka Enberg
2011-07-07 20:12 ` Christoph Lameter
2011-07-08 5:23 ` Andi Kleen
2011-07-08 17:41 ` Christoph Lameter [this message]
2011-07-08 5:38 ` Pekka Enberg
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