From mboxrd@z Thu Jan 1 00:00:00 1970 From: Grant Grundler Subject: Re: copy_user_page_asm suggested 64bit improvment [Was: [parisc-linux] clear user page test] Date: Fri, 31 Dec 2004 13:56:22 -0700 Message-ID: <20041231205622.GA24116@colo.lackof.org> References: <418A80E8000124B5@mail-6-bnl.tiscali.it> <41CFE6B1.6010707@tiscali.be> <1104160093.5295.8.camel@mulgrave> <200412311426.13425.mszick@wolfbutter.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: parisc-linux@lists.parisc-linux.org To: "Michael S. Zick" Return-Path: In-Reply-To: <200412311426.13425.mszick@wolfbutter.com> List-Id: parisc-linux developers list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: parisc-linux-bounces@lists.parisc-linux.org On Fri, Dec 31, 2004 at 02:26:13PM -0600, Michael S. Zick wrote: > This path should not be within the set of user observable execution times. ... > NOTE: Zeroing a page on return to (any) free pool is not 'user observable' only > the 'add to free pool incoming queue' is in the 'user observable' code path. > > NOTE: Pages handled by this daemon may have both d-cache and i-cache > representations. But the code which deals with this situation is not 'user > observable' because the entire 'return to free pool' operation is not 'user > observable'. ... > Q.E.D: Zeroing a page with the destination of user space assignment need not > be a 'user observable' execution time. Mike, The copy_user_page and zero_page functions *are* observable since they affect metrics reported by "time" and readprofile. I don't care if they are in invoked in the application context or some other context. Certainly, it would reduce startup latency to pre-zero the pages in the kernel (daemon) and have them ready when apps want them. But on a loaded system, I expect this will be slightly less efficient and more complex since one doesn't know how many need to be pre-zero'd or when to steal pre-zero'd pages for other uses (e.g. load in an executable). > There should be additional gains made in 'copy-[to|from]-user' when these four > conditions are enforced. I read the conditions and thought "neat". I don't pretend to understand all of them or what they mean. But instead of trying to explain them, could you send me a patch that works? Maybe something that has a chance of going back upstream to linus? thanks, grant > > Mike > _______________________________________________ > parisc-linux mailing list > parisc-linux@lists.parisc-linux.org > http://lists.parisc-linux.org/mailman/listinfo/parisc-linux _______________________________________________ parisc-linux mailing list parisc-linux@lists.parisc-linux.org http://lists.parisc-linux.org/mailman/listinfo/parisc-linux