Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932396Ab0BPAZV (ORCPT ); Mon, 15 Feb 2010 19:25:21 -0500 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:54472 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932313Ab0BPAZT (ORCPT ); Mon, 15 Feb 2010 19:25:19 -0500 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Date: Tue, 16 Feb 2010 09:21:47 +0900 From: KAMEZAWA Hiroyuki To: David Rientjes Cc: Andrew Morton , Rik van Riel , Nick Piggin , Andrea Arcangeli , Balbir Singh , 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 Message-Id: <20100216092147.85ef7619.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: References: <20100216085706.c7af93e1.kamezawa.hiroyu@jp.fujitsu.com> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 2.7.1 (GTK+ 2.10.14; i686-pc-mingw32) 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 Content-Length: 3289 Lines: 74 On Mon, 15 Feb 2010 16:10:15 -0800 (PST) David Rientjes wrote: > On Tue, 16 Feb 2010, KAMEZAWA Hiroyuki wrote: > > > > If memory has been depleted in lowmem zones even with the protection > > > afforded to it by /proc/sys/vm/lowmem_reserve_ratio, it is unlikely that > > > killing current users will help. The memory is either reclaimable (or > > > migratable) already, in which case we should not invoke the oom killer at > > > all, or it is pinned by an application for I/O. Killing such an > > > application may leave the hardware in an unspecified state and there is > > > no guarantee that it will be able to make a timely exit. > > > > > > Lowmem allocations are now failed in oom conditions so that the task can > > > perhaps recover or try again later. Killing current is an unnecessary > > > result for simply making a GFP_DMA or GFP_DMA32 page allocation and no > > > lowmem allocations use the now-deprecated __GFP_NOFAIL bit so retrying is > > > unnecessary. > > > > > > Previously, the heuristic provided some protection for those tasks with > > > CAP_SYS_RAWIO, but this is no longer necessary since we will not be > > > killing tasks for the purposes of ISA allocations. > > > > > > high_zoneidx is gfp_zone(gfp_flags), meaning that ZONE_NORMAL will be the > > > default for all allocations that are not __GFP_DMA, __GFP_DMA32, > > > __GFP_HIGHMEM, and __GFP_MOVABLE on kernels configured to support those > > > flags. Testing for high_zoneidx being less than ZONE_NORMAL will only > > > return true for allocations that have either __GFP_DMA or __GFP_DMA32. > > > > > > Acked-by: Rik van Riel > > > Reviewed-by: KOSAKI Motohiro > > > Signed-off-by: David Rientjes > > > --- > > > mm/page_alloc.c | 3 +++ > > > 1 files changed, 3 insertions(+), 0 deletions(-) > > > > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > > --- a/mm/page_alloc.c > > > +++ b/mm/page_alloc.c > > > @@ -1914,6 +1914,9 @@ rebalance: > > > * running out of options and have to consider going OOM > > > */ > > > if (!did_some_progress) { > > > + /* The oom killer won't necessarily free lowmem */ > > > + if (high_zoneidx < ZONE_NORMAL) > > > + goto nopage; > > > if ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY)) { > > > if (oom_killer_disabled) > > > goto nopage; > > > > WARN_ON((high_zoneidx < ZONE_NORMAL) && (gfp_mask & __GFP_NOFAIL)) > > plz. > > > > As I already explained when you first brought this up, the possibility of > not invoking the oom killer is not unique to GFP_DMA, it is also possible > for GFP_NOFS. Since __GFP_NOFAIL is deprecated and there are no current > users of GFP_DMA | __GFP_NOFAIL, that warning is completely unnecessary. > We're not adding any additional __GFP_NOFAIL allocations. > Please add documentation about that to gfp.h before doing this. Doing this without writing any documenation is laziness. (WARNING is a style of documentation.) Thanks, -Kame -- 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/