From owner-cvs-src@FreeBSD.ORG Thu Mar 27 11:05:14 2003 Return-Path: Delivered-To: cvs-src@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id C76BF37B40B; Thu, 27 Mar 2003 11:05:13 -0800 (PST) Received: from cirb503493.alcatel.com.au (c18609.belrs1.nsw.optusnet.com.au [210.49.80.204]) by mx1.FreeBSD.org (Postfix) with ESMTP id 98EFD43FBF; Thu, 27 Mar 2003 11:05:07 -0800 (PST) (envelope-from peterjeremy@optushome.com.au) Received: from cirb503493.alcatel.com.au (localhost.alcatel.com.au [127.0.0.1])h2RJ56M2019963; Fri, 28 Mar 2003 06:05:06 +1100 (EST) (envelope-from jeremyp@cirb503493.alcatel.com.au) Received: (from jeremyp@localhost) by cirb503493.alcatel.com.au (8.12.8/8.12.8/Submit) id h2RJ54Z7019962; Fri, 28 Mar 2003 06:05:04 +1100 (EST) Date: Fri, 28 Mar 2003 06:05:04 +1100 From: Peter Jeremy To: Dag-Erling =?iso-8859-1?Q?Sm=F8rgrav?= Message-ID: <20030327190504.GD11307@cirb503493.alcatel.com.au> References: <20030326225530.G2075@odysseus.silby.com> <20030327180247.D1825@gamplex.bde.org> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.4.1i X-Spam-Status: No, hits=-29.7 required=5.0 tests=AWL,EMAIL_ATTRIBUTION,IN_REP_TO,REFERENCES, REPLY_WITH_QUOTES,USER_AGENT_MUTT version=2.50 X-Spam-Level: X-Spam-Checker-Version: SpamAssassin 2.50 (1.173-2003-02-20-exp) cc: cvs-src@freebsd.org cc: src-committers@freebsd.org cc: cvs-all@freebsd.org Subject: Re: Checksum/copy X-BeenThere: cvs-src@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: CVS commit messages for the src tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 27 Mar 2003 19:05:17 -0000 [I think this is getting somewhat off topic for the CVS lists] On Thu, Mar 27, 2003 at 09:57:35AM +0100, Dag-Erling Smørgrav wrote: >Might it be a good idea to have separate b{copy,zero} implementations >for special purposes like pmap_{copy,zero}_page? Since these cases >copy or zero a fixed and relatively large amount of data, they should >lend themselves well to optimization. I think it would be useful - even ignoring SSE, most of the fast b{zero,copy} implementations include a fair amount of special code to handle alignment issues and the odd few bytes at the beginning/end that don't fit into the main loop's work unit. Having a known size and alignment simplifies the code a lot. > Zeroing a 4096-byte page on an >SSE-enabled i386 should take no more than 35 SSE instructions The downside is that we need multiple implementations to take advantage of features available in different CPUs. I guess it's a "put up your patches and benchmark results" issue. Peter