From: Andi Kleen <andi@firstfloor.org>
To: Christoph Lameter <cl@linux.com>
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: Thu, 07 Jul 2011 22:23:45 -0700 [thread overview]
Message-ID: <m2box5cplq.fsf@firstfloor.org> (raw)
In-Reply-To: <alpine.DEB.2.00.1107071511010.26083@router.home> (Christoph Lameter's message of "Thu, 7 Jul 2011 15:12:52 -0500 (CDT)")
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.
-Andi
--
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next prev parent reply other threads:[~2011-07-08 5:25 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-26 19:39 [PATCH] slub: reduce overhead of slub_debug 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 [this message]
2011-07-08 17:41 ` Christoph Lameter
2011-07-08 5:38 ` Pekka Enberg
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