Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753779Ab0BWVMp (ORCPT ); Tue, 23 Feb 2010 16:12:45 -0500 Received: from smtp-out.google.com ([216.239.33.17]:43454 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753496Ab0BWVMo (ORCPT ); Tue, 23 Feb 2010 16:12:44 -0500 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=date:from:x-x-sender:to:cc:subject:in-reply-to:message-id: references:user-agent:mime-version:content-type:x-system-of-record; b=LbdCwtAE8GQI9Jq0YxepNgShvI9nNFU0M9q2RB1wfF1z5T4wjV9FyMNgH1T1pJj+X Uh3vCKX9BUcrMvLlvv/RQ== Date: Tue, 23 Feb 2010 13:12:29 -0800 (PST) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Balbir Singh cc: KAMEZAWA Hiroyuki , Nick Piggin , Andrew Morton , Rik van Riel , Andrea Arcangeli , Lubos Lunak , KOSAKI Motohiro , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [patch -mm 8/9 v2] oom: avoid oom killer for lowmem allocations In-Reply-To: <20100223112431.GA8871@balbir.in.ibm.com> Message-ID: References: <20100216085706.c7af93e1.kamezawa.hiroyu@jp.fujitsu.com> <20100216064402.GC5723@laptop> <20100216075330.GJ5723@laptop> <20100217084858.fd72ec4f.kamezawa.hiroyu@jp.fujitsu.com> <20100217090303.6bd64209.kamezawa.hiroyu@jp.fujitsu.com> <20100223112431.GA8871@balbir.in.ibm.com> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1618 Lines: 34 On Tue, 23 Feb 2010, Balbir Singh wrote: > > out_of_memory() doesn't return a value to specify whether the page > > allocator should retry the allocation or just return NULL, all that policy > > is kept in mm/page_alloc.c. For highzone_idx < ZONE_NORMAL, we want to > > fail the allocation when !(gfp_mask & __GFP_NOFAIL) and call the oom > > killer when it's __GFP_NOFAIL. > > --- > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -1696,6 +1696,9 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order, > > /* The OOM killer will not help higher order allocs */ > > if (order > PAGE_ALLOC_COSTLY_ORDER) > > goto out; > > + /* The OOM killer does not needlessly kill tasks for lowmem */ > > + if (high_zoneidx < ZONE_NORMAL) > > + goto out; > > I am not sure if this is a good idea, ZONE_DMA could have a lot of > memory on some architectures. IIUC, we return NULL for allocations > from ZONE_DMA? What is the reason for the heuristic? > As the patch description says, we would otherwise needlessly kill tasks that may not be consuming any lowmem since there is no way to determine its usage and typically the memory in lowmem will either be reclaimable (or migratable via memory compaction) if it is not pinned for I/O in which case we shouldn't kill for it anyway at this point. -- 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/