linux-kernel - Re: replace "memset(...,0,PAGE_SIZE)" calls with "clear

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Date:	Sun, 31 Dec 2006 14:39:02 +0100
From:	Folkert van Heusden <folkert@...heusden.com>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	"Robert P. J. Day" <rpjday@...dspring.com>,
	Denis Vlasenko <vda.linux@...glemail.com>,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: replace "memset(...,0,PAGE_SIZE)" calls with "clear_page()"?

> > i don't see how that can be true, given that most of the definitions
> > of the clear_page() macro are simply invocations of memset().  see for
> > yourself:
> *MOST*. Not all.
> For example an SSE version will at least assume 16 byte alignment, etc
> etc.

What about an if (adress & 15) { memset } else { sse stuff }
or is that too obvious? :-)

> clear_page() is supposed to be for full real pages only... for example
> it allows the architecture to optimize for alignment, cache aliasing etc
> etc. (and if there are cpus that get a "clear an entire page"
> instruction.... there has been hardware like that in the past, even on
> x86, just it's no longer sold afaik)


Folkert van Heusden

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