Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751766AbXBCKQe (ORCPT ); Sat, 3 Feb 2007 05:16:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751670AbXBCKQe (ORCPT ); Sat, 3 Feb 2007 05:16:34 -0500 Received: from pentafluge.infradead.org ([213.146.154.40]:51942 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750863AbXBCKQd (ORCPT ); Sat, 3 Feb 2007 05:16:33 -0500 Date: Sat, 3 Feb 2007 10:16:28 +0000 From: Christoph Hellwig To: Christoph Lameter Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Nick Piggin , KAMEZAWA Hiroyuki , Rik van Riel Subject: Re: [RFC] Tracking mlocked pages and moving them off the LRU Message-ID: <20070203101628.GB28806@infradead.org> Mail-Followup-To: Christoph Hellwig , Christoph Lameter , linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Nick Piggin , KAMEZAWA Hiroyuki , Rik van Riel References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.2i X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1696 Lines: 36 On Fri, Feb 02, 2007 at 10:20:12PM -0800, Christoph Lameter wrote: > This is a new variation on the earlier RFC for tracking mlocked pages. > We now mark a mlocked page with a bit in the page flags and remove > them from the LRU. Pages get moved back when no vma that references > the page has VM_LOCKED set anymore. > > This means that vmscan no longer uselessly cycles over large amounts > of mlocked memory should someone attempt to mlock large amounts of > memory (may even result in a livelock on large systems). > > Synchronization is build around state changes of the PageMlocked bit. > The NR_MLOCK counter is incremented and decremented based on > state transitions of PageMlocked. So the count is accurate. > > There is still some unfinished business: > > 1. We use the 21st page flag and we only have 20 on 32 bit NUMA platforms. > > 2. Since mlocked pages are now off the LRU page migration will no longer > move them. > > 3. Use NR_MLOCK to tune various VM behaviors so that the VM does not > longer fall due to too many mlocked pages in certain areas. This patch seems to not handle the cases where more than one process mlocks a page and you really need a pincount in the page to not release it before all processes have munlock it or died. I did a similar patch a while ago and tried to handle it by overloading the lru lists pointers with a pincount, but at some point I gave up because I couldn't get that part right. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/