linux-kernel - Re: [PATCH] slub: reduce overhead of slub

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 07 Jul 2011 22:23:45 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Pekka Enberg <penberg@...nel.org>,
	David Miller <davem@...emloft.net>, marcin.slusarz@...il.com,
	mpm@...enic.com, linux-kernel@...r.kernel.org, rientjes@...gle.com,
	linux-mm@...ck.org
Subject: Re: [PATCH] slub: reduce overhead of slub_debug

Christoph Lameter <cl@...ux.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

-- 
ak@...ux.intel.com -- Speaking for myself only
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/