From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755183Ab1IFPwK (ORCPT ); Tue, 6 Sep 2011 11:52:10 -0400 Received: from mail-yi0-f46.google.com ([209.85.218.46]:42367 "EHLO mail-yi0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755113Ab1IFPwF (ORCPT ); Tue, 6 Sep 2011 11:52:05 -0400 Date: Wed, 7 Sep 2011 00:51:41 +0900 From: Minchan Kim To: Mel Gorman Cc: Johannes Weiner , Andrew Morton , linux-mm , LKML , Rik van Riel , KOSAKI Motohiro Subject: Re: [PATCH] vmscan: Do reclaim stall in case of mlocked page. Message-ID: <20110906155141.GB1589@barrios-fedora.local> References: <1321285043-3470-1-git-send-email-minchan.kim@gmail.com> <20110831173031.GA21571@redhat.com> <20110905083321.GA15935@redhat.com> <20110906151140.GA1589@barrios-fedora.local> <20110906153903.GU14369@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110906153903.GU14369@suse.de> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 06, 2011 at 04:39:03PM +0100, Mel Gorman wrote: > On Wed, Sep 07, 2011 at 12:11:40AM +0900, Minchan Kim wrote: > > > > > > > > If we consider that, we have to fix other reset_reclaim_mode cases as > > > > well as mlocked pages. > > > > Or > > > > fix isolataion logic for the lumpy? (When we find the page isn't able > > > > to isolate, rollback the pages in the lumpy block to the LRU) > > > > Or > > > > Nothing and wait to remove lumpy completely. > > > > > > > > What do you think about it? > > > > > > The rollback may be overkill and we already abort clustering the > > > isolation when one of the pages fails. > > > > I think abort isn't enough > > Because we know the chace to make a bigger page is gone when we isolate page. > > But we still try to reclaim pages to make bigger space in a vain. > > It causes unnecessary unmap operation by try_to_unmap which is costly operation > > , evict some working set pages and make reclaim latency long. > > > > As a matter of fact, I though as follows patch to solve this problem(Totally, untested) > > > > I confess I haven't read this patch carefully or given it much > thought. I agree with you in principal that it would be preferred if > lumpy reclaim disrupted the LRU lists as little as possible but I'm > wary about making lumpy reclaim more complex when it is preferred that > compaction is used and we expect lumpy reclaim to go away eventually. Agreed. But I think the concept of the patch could be applied to compaction for high order pages. If we know some block has a pinned page when we do compaction for high order pages, migration of the pages isolated in the block is pointless. > > > > > > > > > > I would go with the last option. Lumpy reclaim is on its way out and > > > already disabled for a rather common configuration, so I would defer > > > non-obvious fixes like these until actual bug reports show up. > > > > It's hard to report above problem as it might not make big difference on normal worklaod. > > I doubt it makes a noticable difference as lumpy reclaim disrupts > the system quite heavily. Yes. I don't know such workload but I think it apparently could make relcaim latency long with be not able to make bigger page. > > > But I agree last option, too. Then, when does we suppose to remove lumpy? > > Mel, Could you have a any plan? > > > > I think it should be removed after all the major distributions release > with a kernel with compaction enabled. At that point, we'll know > that lumpy reclaim is not being depended upon. It does make sense. > > -- > Mel Gorman > SUSE Labs