Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755027Ab1CXGQb (ORCPT ); Thu, 24 Mar 2011 02:16:31 -0400 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:36626 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753772Ab1CXGQa (ORCPT ); Thu, 24 Mar 2011 02:16:30 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 From: KOSAKI Motohiro To: Minchan Kim Subject: Re: [PATCH 1/5] vmscan: remove all_unreclaimable check from direct reclaim path completely Cc: kosaki.motohiro@jp.fujitsu.com, linux-kernel@vger.kernel.org, Andrew Morton , David Rientjes , Linus Torvalds , Rik van Riel , Oleg Nesterov , linux-mm , Andrey Vagin , Hugh Dickins , KAMEZAWA Hiroyuki , Nick Piggin , Johannes Weiner In-Reply-To: References: <20110324143541.CC78.A69D9226@jp.fujitsu.com> Message-Id: <20110324151701.CC7F.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Mailer: Becky! ver. 2.56.05 [ja] Date: Thu, 24 Mar 2011 15:16:25 +0900 (JST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1807 Lines: 57 Hi > Thanks for your effort, Kosaki. > But I still doubt this patch is good. > > This patch makes early oom killing in hibernation as it skip > all_unreclaimable check. > Normally, hibernation needs many memory so page_reclaim pressure > would be big in small memory system. So I don't like early give up. Wait. When occur big pressure? hibernation reclaim pressure (sc->nr_to_recliam) depend on physical memory size. therefore a pressure seems to don't depend on the size. > Do you think my patch has a problem? Personally, I think it's very > simple and clear. :) To be honest, I dislike following parts. It's madness on madness. static bool zone_reclaimable(struct zone *zone) { if (zone->all_unreclaimable) return false; return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; } The function require a reviewer know o pages_scanned and all_unreclaimable are racy o at hibernation, zone->all_unreclaimable can be false negative, but can't be false positive. And, a function comment of all_unreclaimable() says /* * As hibernation is going on, kswapd is freezed so that it can't mark * the zone into all_unreclaimable. It can't handle OOM during hibernation. * So let's check zone's unreclaimable in direct reclaim as well as kswapd. */ But, now it is no longer copy of kswapd algorithm. If you strongly prefer this idea even if you hear above explanation, please consider to add much and much comments. I can't say current your patch is enough readable/reviewable. Thanks. -- 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/