From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 17 Sep 2001 04:15:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 17 Sep 2001 04:15:24 -0400 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:47952 "EHLO flinx.biederman.org") by vger.kernel.org with ESMTP id ; Mon, 17 Sep 2001 04:15:14 -0400 To: Rik van Riel Cc: , Subject: Re: broken VM in 2.4.10-pre9 In-Reply-To: From: ebiederm@xmission.com (Eric W. Biederman) Date: 17 Sep 2001 02:06:46 -0600 In-Reply-To: Message-ID: User-Agent: Gnus/5.0808 (Gnus v5.8.8) Emacs/20.5 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Rik van Riel writes: > On 16 Sep 2001, Michael Rothwell wrote: > > > Is there a way to tell the VM to prune its cache? Or a way to limit > > the amount of cache it uses? > > Not yet, I'll make a quick hack for this when I get back next > week. It's pretty obvious now that the 2.4 kernel cannot get > enough information to select the right pages to evict from > memory. Hmm. Perhaps or perhaps it is using the information poorly. There is an alternative approach to have better aging information. An address_space can be allocated per mm_struct. And all of the anonymous pages can be allocated to that address_space. The address_space can then have an array or better a tree of extents that list which indexes correspond to which swap pages. With some pages not being backed. Getting the allocation of indices correct so that merging will work is a little trickier then now, as is the case of a private writeable mapping of a file. But in a lot of other ways the logic becomes simpler. > For 2.5 I'm making a VM subsystem with reverse mappings, the > first iterations are giving very sweet performance so I will > continue with this project regardless of what other kernel > hackers might say ;) Do you have any arguments for the reverse mappings or just for some of the other side effects that go along with them? Eric