From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: broken VM in 2.4.10-pre9 References: From: ebiederm@xmission.com (Eric W. Biederman) Date: 17 Sep 2001 09:45:49 -0600 In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org Return-Path: To: Rik van Riel Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: Rik van Riel writes: > On 17 Sep 2001, Eric W. Biederman wrote: > > > There is an alternative approach to have better aging information. > > [snip incomplete description of data structure] > > What you didn't explain is how your idea is related to > aging. Sorry I thought you had been staring at the problem long enough to see. In any case the problem with the current code is that you can't put all pages in the swap cache immediately because you don't want to allocate the swap space just yet. And without being in the swap cache aging isn't especially effective. By using something like a shared memory segment behind every anonymous page, you can put the page in the swap cache before you allocate swap for it (because it has a persistent identity). Further since you no longer need counts for every swap page. You can deallocate swap space from pages simply by walking through the ``indirect pages'' and removing the reference to swap space. > > > 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? > > Mainly for the side effects, but until somebody comes > up with another idea to achieve all the side effects I'm > not giving up on reverse mappings. If you can achieve > all the good stuff in another way, show it. I think I can I haven't had time to implement it. Given the way Alan and some of the others were talking I though my idea has long ago been thought of and put on the plate for 2.5. If it really is a new idea under the sun I'll look at implementing it as soon as I have a hole in my schedule. Eric -- 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/