linux-kernel - Re: [patch] x86, mm: pass in 'total' to __copy_from_user

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: <200903021718.12402.nickpiggin@yahoo.com.au>
Date:	Mon, 2 Mar 2009 17:18:11 +1100
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Arjan van de Ven <arjan@...radead.org>,
	Andi Kleen <andi@...stfloor.org>,
	David Miller <davem@...emloft.net>,
	torvalds@...ux-foundation.org, mingo@...e.hu, sqazi@...gle.com,
	linux-kernel@...r.kernel.org, tglx@...utronix.de
Subject: Re: [patch] x86, mm: pass in 'total' to __copy_from_user_*nocache()

On Monday 02 March 2009 15:46:03 H. Peter Anvin wrote:
> Nick Piggin wrote:
> > I would expect any high performance CPU these days to combine entries
> > in the store queue, even for normal store instructions (especially for
> > linear memcpy patterns). Isn't this likely to be the case?
>
> Actually, that is often not the case simply because it doesn't buy that
> much.  The big win comes when you don't read a whole cache line in from
> memory, but that is a property of the cache, not the store queue.

Hm, maybe I'm confused. As far as I thought, you could avoid the
RMW write allocate behaviour by bypassing the cache on a store
miss, or combining stores into cacheline blocks before they leave
the store queue.

--
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/