From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 23 Oct 2002 00:23:19 +0200 From: bert hubert Subject: Re: vm scenario tool / mincore(2) functionality for regular pages? Message-ID: <20021022222319.GA18272@outpost.ds9a.nl> References: <20021022184313.GA12081@outpost.ds9a.nl> <3DB5BBFC.479BE5DD@digeo.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3DB5BBFC.479BE5DD@digeo.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Ingo Molnar List-ID: On Tue, Oct 22, 2002 at 01:58:36PM -0700, Andrew Morton wrote: > mincore needs to be taught to walk pagetables and to look up > stuff in swapcache. As mincore appears to be entirely unstandardized, we can get away with extending its functionality. > Also it currently assumes that vma->vm_file is mapped linearly, > so it will return incorrect results with Ingo's nonlinear mapping > extensions. It also appears to fail if the memory range it is offered lives in multiple vmas. I'm unsure if this is possible, but I recall reading about mozilla needing 'vma merging', which seems to imply that a process can have more of them. > But if we were to use Ingo's "file pte's" for all mmappings, mincore > only needs to do the pte->pagecache lookup, so it can lose the > "vma is linear" arithmetic. The pagetable walking and swapcache lookup is orthogonal to this? By the way, version 0.1 which is mildly functional is on http://ds9a.nl/vmloader-0.1.tar.gz , it currently does mincore only for mmapped files. Use 'mkfile name 100' to create a 100mb file, 'map name' to map it. It is interesting to note that 2.4.20-pre9 allows me to allocate 250 megabytes and touch it sequentially without dire behaviour on a 186 megabyte (or so) machine. RSS is a reasonable 153MB afterwards. Reading that 250 megabytes from the start again however causes massive swapping and takes way longer than the initial touching. Probably some kind of 'use once' heuristic that is suddenly disabled. Regards, bert -- http://www.PowerDNS.com Versatile DNS Software & Services http://lartc.org Linux Advanced Routing & Traffic Control HOWTO -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/