Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755398Ab0FPCYy (ORCPT ); Tue, 15 Jun 2010 22:24:54 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:52795 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754875Ab0FPCYw (ORCPT ); Tue, 15 Jun 2010 22:24:52 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Date: Wed, 16 Jun 2010 11:20:24 +0900 From: KAMEZAWA Hiroyuki To: KAMEZAWA Hiroyuki Cc: Rik van Riel , Mel Gorman , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Dave Chinner , Chris Mason , Nick Piggin , Johannes Weiner , Christoph Hellwig , Andrew Morton Subject: Re: [PATCH 12/12] vmscan: Do not writeback pages in direct reclaim Message-Id: <20100616112024.5b093905.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20100616104036.b45d352b.kamezawa.hiroyu@jp.fujitsu.com> References: <1276514273-27693-1-git-send-email-mel@csn.ul.ie> <1276514273-27693-13-git-send-email-mel@csn.ul.ie> <4C16A567.4080000@redhat.com> <20100615114510.GE26788@csn.ul.ie> <4C17815A.8080402@redhat.com> <20100615135928.GK26788@csn.ul.ie> <4C178868.2010002@redhat.com> <20100615141601.GL26788@csn.ul.ie> <20100616091755.7121c7d3.kamezawa.hiroyu@jp.fujitsu.com> <4C181AFD.5060503@redhat.com> <20100616093958.00673123.kamezawa.hiroyu@jp.fujitsu.com> <4C182097.2070603@redhat.com> <20100616104036.b45d352b.kamezawa.hiroyu@jp.fujitsu.com> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 3.0.2 (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: 2052 Lines: 78 On Wed, 16 Jun 2010 10:40:36 +0900 KAMEZAWA Hiroyuki wrote: > On Tue, 15 Jun 2010 20:53:43 -0400 > Rik van Riel wrote: > > > On 06/15/2010 08:39 PM, KAMEZAWA Hiroyuki wrote: > > > > > Hmm, or do you recommend no-dirty-page-writeback when a memcg hits limit ? > > > Maybe we'll see much swaps. > > > > > > I want to go with this for a while, changing memcg's behavior will took > > > some amounts of time, there are only a few developpers. > > > > One thing we can do, for kswapd, memcg and direct reclaim alike, > > is to tell the flusher threads to flush pages related to a pageout > > candidate page to disk. > > > > That way the reclaiming processes can wait on some disk IO to > > finish, while the flusher thread takes care of the actual flushing. > > > > That should also fix the "kswapd filesystem IO has really poor IO > > patterns" issue. > > > > There's no reason not to fix this issue the right way. > > > yes. but this patch just stops writeback. I think it's sane to ask > not to change behavior until there are some useful changes in flusher > threads. > > IMO, until flusher threads can work with I/O cgroup, memcg shoudln't > depend on it because writeback allows stealing resource without it. > BTW, copy_from_user/copy_to_user is _real_ problem, I'm afraid following much more than memcg. handle_mm_fault() -> handle_pte_fault() -> do_wp_page() -> balance_dirty_page_rate_limited() -> balance_dirty_pages() -> writeback_inodes_wbc() -> writeback_inodes_wb() -> writeback_sb_inodes() -> writeback_single_inode() -> do_writepages() -> generic_write_pages() -> write_cache_pages() // use on-stack pagevec. -> writepage() maybe much more stack consuming than memcg->writeback after vmscan.c diet. Bye. -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/