Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756071Ab1DZGN4 (ORCPT ); Tue, 26 Apr 2011 02:13:56 -0400 Received: from mga01.intel.com ([192.55.52.88]:44834 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755335Ab1DZGNz (ORCPT ); Tue, 26 Apr 2011 02:13:55 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.64,267,1301900400"; d="scan'208";a="914417217" Date: Tue, 26 Apr 2011 14:13:53 +0800 From: Wu Fengguang To: Dave Young Cc: linux-mm , Linux Kernel Mailing List Subject: Re: readahead and oom Message-ID: <20110426061353.GA19717@localhost> References: <20110426055521.GA18473@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1646 Lines: 48 On Tue, Apr 26, 2011 at 02:05:12PM +0800, Dave Young wrote: > On Tue, Apr 26, 2011 at 1:55 PM, Wu Fengguang wrote: > > On Tue, Apr 26, 2011 at 01:49:25PM +0800, Dave Young wrote: > >> Hi, > >> > >> When memory pressure is high, readahead could cause oom killing. > >> IMHO we should stop readaheading under such circumstances。If it's true > >> how to fix it? > > > > Good question. Before OOM there will be readahead thrashings, which > > can be addressed by this patch: > > > > http://lkml.org/lkml/2010/2/2/229 > > Hi, I'm not clear about the patch, could be regard as below cases? > 1) readahead alloc fail due to low memory such as other large allocation > 2) readahead thrashing caused by itself When memory pressure goes up (not as much as allocation failures and OOM), the readahead pages may be reclaimed before they are read() accessed by the user space. At the time read() asks for the page, it will have to be read from disk _again_. This is called readahead thrashing. What the patch does is to automatically detect readahead thrashing and shrink the readahead size adaptively, which will the reduce memory consumption by readahead buffers. Thanks, Fengguang > > > > However there seems no much interest on that feature.. I can separate > > that out and resubmit it standalone if necessary. > > > > Thanks, > > Fengguang > > > > > > -- > Regards > dave -- 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/