From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758524AbZFPMak (ORCPT ); Tue, 16 Jun 2009 08:30:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757680AbZFPMaY (ORCPT ); Tue, 16 Jun 2009 08:30:24 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:59525 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755204AbZFPMaW (ORCPT ); Tue, 16 Jun 2009 08:30:22 -0400 From: KOSAKI Motohiro To: Mel Gorman Subject: Re: [PATCH 0/3] Fix malloc() stall in zone_reclaim() and bring behaviour more in line with expectations V3 Cc: kosaki.motohiro@jp.fujitsu.com, Christoph Lameter , Andrew Morton , riel@redhat.com, fengguang.wu@intel.com, linuxram@us.ibm.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Johannes Weiner In-Reply-To: <20090616122056.GC14241@csn.ul.ie> References: <20090616202210.99B2.A69D9226@jp.fujitsu.com> <20090616122056.GC14241@csn.ul.ie> Message-Id: <20090616212935.99B8.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Becky! ver. 2.50.07 [ja] Date: Tue, 16 Jun 2009 21:30:21 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Tue, Jun 16, 2009 at 09:08:47PM +0900, KOSAKI Motohiro wrote: > > > On Mon, Jun 15, 2009 at 11:01:41AM -0400, Christoph Lameter wrote: > > > > On Mon, 15 Jun 2009, Mel Gorman wrote: > > > > > > > > > > May I ask your worry? > > > > > > > > > > > > > > > > Simply that I believe the intention of PF_SWAPWRITE here was to allow > > > > > zone_reclaim() to aggressively reclaim memory if the reclaim_mode allowed > > > > > it as it was a statement that off-node accesses are really not desired. > > > > > > > > Right. > > > > > > > > > Ok. I am not fully convinced but I'll not block it either if believe it's > > > > > necessary. My current understanding is that this patch only makes a difference > > > > > if the server is IO congested in which case the system is struggling anyway > > > > > and an off-node access is going to be relatively small penalty overall. > > > > > Conceivably, having PF_SWAPWRITE set makes things worse in that situation > > > > > and the patch makes some sense. > > > > > > > > We could drop support for RECLAIM_SWAP if that simplifies things. > > > > > > > > > > I don't think that is necessary. While I expect it's very rarely used, I > > > imagine a situation where it would be desirable on a system that had large > > > amounts of tmpfs pages but where it wasn't critical they remain in-memory. > > > > > > Removing PF_SWAPWRITE would make it less aggressive and if you were > > > happy with that, then that would be good enough for me. > > > > I surprised this a bit. I've imazined Christoph never agree to remove it. > > Currently, trouble hitting user of mine don't use this feature. Thus, if it can be > > removed, I don't need to worry abusing this again and I'm happy. > > > > Mel, Have you seen actual user of this? > > > > No, but then again the usage for it is quite specific. Namely for use on > systems that uses a large amount of tmpfs where the remote NUMA penalty is > high and it's acceptable to swap tmpfs pages to avoid remote accesses. I > don't see the harm in having the option available. ok. I understand your opinion. Thanks.