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From: Arjan van de Ven <arjan@infradead.org>
To: Folkert van Heusden <folkert@vanheusden.com>
Cc: "Robert P. J. Day" <rpjday@mindspring.com>,
	Denis Vlasenko <vda.linux@googlemail.com>,
	Linux kernel mailing list <linux-kernel@vger.kernel.org>
Subject: Re: replace "memset(...,0,PAGE_SIZE)" calls with "clear_page()"?
Date: Sun, 31 Dec 2006 14:45:34 +0100	[thread overview]
Message-ID: <1167572735.20929.750.camel@laptopd505.fenrus.org> (raw)
In-Reply-To: <20061231133902.GA13521@vanheusden.com>

On Sun, 2006-12-31 at 14:39 +0100, Folkert van Heusden wrote:
> > > 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? :-)


it's only one example. clear_page() working only on a full page is a
nice restriction that allows the implementation to be optimized (again
the x86 hardware that had a hardware page zeroer comes to mind, the hw
is only 4 years old or so... and future hw may have it again)

clear_page() is more restricted than memset(). And that's good, it
allows for a more focused implementation. Otherwise there'd be no reason
to HAVE a clear_page(), if it just was a memset wrapper entirely.



-- 
if you want to mail me at work (you don't), use arjan (at) linux.intel.com
Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org


  reply	other threads:[~2006-12-31 13:45 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-12-29  6:16 Robert P. J. Day
2006-12-30 20:49 ` Denis Vlasenko
2006-12-30 22:08   ` Robert P. J. Day
2006-12-30 22:40     ` Denis Vlasenko
2007-01-03  6:23       ` dean gaudet
2006-12-30 22:45     ` Arjan van de Ven
2006-12-30 23:04       ` Robert P. J. Day
2006-12-31 18:39         ` Paul Mundt
2006-12-31 19:04           ` Robert P. J. Day
2007-01-01  1:59             ` Folkert van Heusden
2007-01-01  8:33               ` Robert P. J. Day
2007-01-01 10:14                 ` Arjan van de Ven
2007-01-01 10:27                   ` Robert P. J. Day
2007-01-01 19:05                     ` Dave Jones
2007-01-01  8:42               ` Paul Mundt
2007-01-01 17:09                 ` Randy Dunlap
2006-12-31 13:39       ` Folkert van Heusden
2006-12-31 13:45         ` Arjan van de Ven [this message]
2006-12-31 16:39           ` Robert P. J. Day
2006-12-31 17:43             ` Arjan van de Ven
2007-01-03 13:20               ` Robert P. J. Day

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