From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757400AbZGPDwE (ORCPT ); Wed, 15 Jul 2009 23:52:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757390AbZGPDwD (ORCPT ); Wed, 15 Jul 2009 23:52:03 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:44018 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757368AbZGPDwB (ORCPT ); Wed, 15 Jul 2009 23:52:01 -0400 Date: Wed, 15 Jul 2009 20:51:09 -0700 From: Andrew Morton To: Rik van Riel Cc: KOSAKI Motohiro , LKML , linux-mm , Wu Fengguang Subject: Re: [PATCH -mm] throttle direct reclaim when too many pages are isolated already Message-Id: <20090715205109.5f86e416.akpm@linux-foundation.org> In-Reply-To: <4A5EA1A4.1080502@redhat.com> References: <20090715223854.7548740a@bree.surriel.com> <20090715194820.237a4d77.akpm@linux-foundation.org> <4A5E9A33.3030704@redhat.com> <20090715202114.789d36f7.akpm@linux-foundation.org> <4A5E9E4E.5000308@redhat.com> <20090715203854.336de2d5.akpm@linux-foundation.org> <4A5EA1A4.1080502@redhat.com> X-Mailer: Sylpheed 2.4.8 (GTK+ 2.12.5; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 15 Jul 2009 23:42:28 -0400 Rik van Riel wrote: > Andrew Morton wrote: > > On Wed, 15 Jul 2009 23:28:14 -0400 Rik van Riel wrote: > > >> If we are stuck at this point in the page reclaim code, > >> it is because too many other tasks are reclaiming pages. > >> > >> That makes it fairly safe to just return SWAP_CLUSTER_MAX > >> here and hope that __alloc_pages() can get a page. > >> > >> After all, if __alloc_pages() thinks it made progress, > >> but still cannot make the allocation, it will call the > >> pageout code again. > > > > Which will immediately return because the caller still has > > fatal_signal_pending()? > > Other processes are in the middle of freeing pages at > this point, so we should succeed in __alloc_pages() > fairly quickly (and then die and free all our memory). What if it's a uniprocessor machine and all those processes are scheduled out? We sit there chewing 100% CPU and not doing anything afaict. Even if it _is_ SMP, we could still chew decent-sized blips of CPU time rattling around waiting for something to happen.