linux-kernel - Re: [PATCH] x86: eliminate redundant/contradicting cache line size config options

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]

Message-Id: <4B0512060200007800020C42@vpn.id2.novell.com>
Date:	Thu, 19 Nov 2009 08:38:14 +0000
From:	"Jan Beulich" <JBeulich@...ell.com>
To:	"Nick Piggin" <npiggin@...e.de>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Arjan van de Ven" <arjan@...radead.org>, <tglx@...utronix.de>,
	"Shai Fultheim" <shai@...lemp.com>,
	"Ravikiran Thirumalai" <kiran@...lex86.org>,
	<linux-kernel@...r.kernel.org>, <hpa@...or.com>
Subject: Re: [PATCH] x86: eliminate redundant/contradicting cache line
	 size config options

>>> Nick Piggin <npiggin@...e.de> 19.11.09 09:13 >>>
>On Wed, Nov 18, 2009 at 08:52:40PM -0800, Arjan van de Ven wrote:
>Basically what I think we should do is consider L1_CACHE_BYTES to be
>*the* correct default value to use for 1) avoiding false sharing (which
>seems to be the most common use), and 2) optimal and repeatable per-object
>packing into cachelines (which is more of a micro-optimization to be
>applied carefully to really critical structures).

But then this really shouldn't be called L1_CACHE_... Though I realize
that the naming seems to already be broken - looking over the cache
line specifiers for CPUID leaf 2, there's really no L1 with 128 byte lines,
just two L2s.

One question however is whether e.g. cache line ping-pong between
L3s is really costing that much on non-NUMA, as opposed to it
happening between L1s.

Jan

--
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/