Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760710AbXHTTA7 (ORCPT ); Mon, 20 Aug 2007 15:00:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753515AbXHTTAv (ORCPT ); Mon, 20 Aug 2007 15:00:51 -0400 Received: from netops-testserver-4-out.sgi.com ([192.48.171.29]:44831 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753491AbXHTTAt (ORCPT ); Mon, 20 Aug 2007 15:00:49 -0400 Date: Mon, 20 Aug 2007 12:00:49 -0700 (PDT) From: Christoph Lameter X-X-Sender: clameter@schroedinger.engr.sgi.com To: Pavel Machek cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, dkegel@google.com, Peter Zijlstra , David Miller , Nick Piggin Subject: Re: [RFC 2/9] Use NOMEMALLOC reclaim to allow reclaim if PF_MEMALLOC is set In-Reply-To: <20070818071035.GA4667@ucw.cz> Message-ID: References: <20070814153021.446917377@sgi.com> <20070814153501.305923060@sgi.com> <20070818071035.GA4667@ucw.cz> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1294 Lines: 28 On Sat, 18 Aug 2007, Pavel Machek wrote: > > The reclaim is of particular important to stacked filesystems that may > > do a lot of allocations in the write path. Reclaim will be working > > as long as there are clean file backed pages to reclaim. > > I don't get it. Lets say that we have stacked filesystem that needs > it. That filesystem is broken today. > > Now you give it second chance by reclaiming clean pages, but there are > no guarantees that we have any.... so that filesystem is still broken > with your patch...? There is a guarantee that we have some because the user space program is executing. Meaning the executable pages can be retrieved. The amount dirty memory in the system is limited by the dirty_ratio. So the VM can only get into trouble if there is a sufficient amount of anonymous pages and all executables have been reclaimed. That is pretty rare. Plus the same issue can happen today. Writes are usually not completed during reclaim. If the writes are sufficiently deferred then you have the same issue now. - 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/