Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753242AbZFHGqR (ORCPT ); Mon, 8 Jun 2009 02:46:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751501AbZFHGqH (ORCPT ); Mon, 8 Jun 2009 02:46:07 -0400 Received: from TYO202.gate.nec.co.jp ([202.32.8.206]:45054 "EHLO tyo202.gate.nec.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751493AbZFHGqG (ORCPT ); Mon, 8 Jun 2009 02:46:06 -0400 Date: Mon, 8 Jun 2009 15:39:16 +0900 From: Daisuke Nishimura To: KOSAKI Motohiro Cc: LKML , linux-mm , Andrew Morton , Johannes Weiner , Balbir Singh , KAMEZAWA Hiroyuki , Daisuke Nishimura Subject: Re: [PATCH mmotm] vmscan: fix may_swap handling for memcg Message-Id: <20090608153916.3ccaeb9a.nishimura@mxp.nes.nec.co.jp> In-Reply-To: <20090608121848.4370.A69D9226@jp.fujitsu.com> References: <20090608120228.cb70e569.nishimura@mxp.nes.nec.co.jp> <20090608121848.4370.A69D9226@jp.fujitsu.com> Organization: NEC Soft, Ltd. X-Mailer: Sylpheed 2.6.0 (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: 2326 Lines: 60 On Mon, 8 Jun 2009 12:20:54 +0900 (JST), KOSAKI Motohiro wrote: > Hi > Hi, thank you for your comment. > > From: Daisuke Nishimura > > > > Commit 2e2e425989080cc534fc0fca154cae515f971cf5 ("vmscan,memcg: reintroduce > > sc->may_swap) add may_swap flag and handle it at get_scan_ratio(). > > > > But the result of get_scan_ratio() is ignored when priority == 0, and this > > means, when memcg hits the mem+swap limit, anon pages can be swapped > > just in vain. Especially when memcg causes oom by mem+swap limit, > > we can see many and many pages are swapped out. > > > > Instead of not scanning anon lru completely when priority == 0, this patch adds > > a hook to handle may_swap flag in shrink_page_list() to avoid using useless swaps, > > and calls try_to_free_swap() if needed because it can reduce > > both mem.usage and memsw.usage if the page(SwapCache) is unused anymore. > > > > Such unused-but-managed-under-memcg SwapCache can be made in some paths, > > for example trylock_page() failure in free_swap_cache(). > > > > Signed-off-by: Daisuke Nishimura > > I think root cause is following branch, right? yes. > if so, Why can't we handle this issue on shrink_zone()? > Just because priority==0 means oom is about to happen and I don't want to see oom if possible. So I thought it would be better to reclaim as much pages(memsw.usage) as possible in this case. > > --------------------------------------------------------------- > static void shrink_zone(int priority, struct zone *zone, > struct scan_control *sc) > { > get_scan_ratio(zone, sc, percent); > > for_each_evictable_lru(l) { > int file = is_file_lru(l); > unsigned long scan; > > scan = zone_nr_pages(zone, sc, l); > if (priority) { // !!here!! > scan >>= priority; > scan = (scan * percent[file]) / 100; > } > > > > -- 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/