Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752469AbZFHDVH (ORCPT ); Sun, 7 Jun 2009 23:21:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751073AbZFHDUz (ORCPT ); Sun, 7 Jun 2009 23:20:55 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:46002 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750950AbZFHDUz (ORCPT ); Sun, 7 Jun 2009 23:20:55 -0400 From: KOSAKI Motohiro To: Daisuke Nishimura Subject: Re: [PATCH mmotm] vmscan: fix may_swap handling for memcg Cc: kosaki.motohiro@jp.fujitsu.com, LKML , linux-mm , Andrew Morton , Johannes Weiner , Balbir Singh , KAMEZAWA Hiroyuki In-Reply-To: <20090608120228.cb70e569.nishimura@mxp.nes.nec.co.jp> References: <20090608120228.cb70e569.nishimura@mxp.nes.nec.co.jp> Message-Id: <20090608121848.4370.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: Mon, 8 Jun 2009 12:20:54 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1907 Lines: 50 Hi > 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? if so, Why can't we handle this issue on shrink_zone()? --------------------------------------------------------------- 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/