Date: Thu, 27 Mar 2003 23:32:35 +0100 From: des@ofug.org (Dag-Erling =?iso-8859-1?q?Sm=F8rgrav?=) To: David Malone <dwmalone@maths.tcd.ie> Cc: cvs-all@FreeBSD.org Subject: Re: Checksum/copy Message-ID: <xzpr88sv3ss.fsf@flood.ping.uio.no> In-Reply-To: <20030327212647.GA64029@walton.maths.tcd.ie> (David Malone's message of "Thu, 27 Mar 2003 21:26:47 %2B0000") References: <Pine.BSF.4.21.0303260956250.27748-100000@root.org> <20030326225530.G2075@odysseus.silby.com> <20030327180247.D1825@gamplex.bde.org> <xzp7kalw5j4.fsf@flood.ping.uio.no> <20030327212647.GA64029@walton.maths.tcd.ie>
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David Malone <dwmalone@maths.tcd.ie> writes:
> On Thu, Mar 27, 2003 at 09:57:35AM +0100, des@ofug.org wrote:
> > Might it be a good idea to have separate b{copy,zero} implementations
> > for special purposes like pmap_{copy,zero}_page?
> We do have a i686_pagezero already, which seems to be used in
> pmap_zero_page - I guess it may not be well tuned to modern processors,
> as it is almost 5 years old.
i686_pagezero uses 'rep stosl' after an initial 'rep scasl' to check
if the page was already zero (which is a pessimization unless we zero
a lot of pages that are already zeroed). SSE can do far better than
that.
DES
--=20
Dag-Erling Sm=F8rgrav - des@ofug.org
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