From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263861AbUBDT4o (ORCPT ); Wed, 4 Feb 2004 14:56:44 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263880AbUBDT4o (ORCPT ); Wed, 4 Feb 2004 14:56:44 -0500 Received: from e5.ny.us.ibm.com ([32.97.182.105]:56793 "EHLO e5.ny.us.ibm.com") by vger.kernel.org with ESMTP id S263861AbUBDT4m (ORCPT ); Wed, 4 Feb 2004 14:56:42 -0500 Subject: Re: Active Memory Defragmentation: Our implementation & problems From: Dave Hansen To: Alok Mooley Cc: linux-kernel , linux-mm In-Reply-To: <20040204185446.91810.qmail@web9705.mail.yahoo.com> References: <20040204185446.91810.qmail@web9705.mail.yahoo.com> Content-Type: text/plain Organization: Message-Id: <1075924593.27981.458.camel@nighthawk> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.2.4 Date: 04 Feb 2004 11:56:33 -0800 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2004-02-04 at 10:54, Alok Mooley wrote: > --- Dave Hansen wrote: > > > The "work until we get interrupted and restart if > > something changes > > state" approach is very, very common. Can you give > > some more examples > > of just how a page fault would ruin the defrag > > process? > > > > What I mean to say is that if we have identified some > pages for movement, & we get preempted, the pages > identified as movable may not remain movable any more > when we are rescheduled. We are left with the task of > identifying new movable pages. Depending on the quantity of work that you're trying to do at once, this might be unavoidable. I know it's a difficult thing to think about, but I still don't understand the precise cases that you're concerned about. Page faults to me seem like the least of your problems. A bigger issue would be if the page is written to by userspace after you copy, but before you install the new pte. Did I miss the code in your patch that invalidated the old tlb entries? --dave