Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759504Ab1FXOpE (ORCPT ); Fri, 24 Jun 2011 10:45:04 -0400 Received: from cantor2.suse.de ([195.135.220.15]:38985 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753973Ab1FXOpB (ORCPT ); Fri, 24 Jun 2011 10:45:01 -0400 From: Mel Gorman To: Andrew Morton Cc: =?UTF-8?q?P=C3=A1draig=20Brady?= , James Bottomley , Colin King , Minchan Kim , Andrew Lutomirski , Rik van Riel , Johannes Weiner , linux-mm , linux-kernel , Mel Gorman Subject: [PATCH 0/4] Stop kswapd consuming 100% CPU when highest zone is small Date: Fri, 24 Jun 2011 15:44:53 +0100 Message-Id: <1308926697-22475-1-git-send-email-mgorman@suse.de> X-Mailer: git-send-email 1.7.3.4 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2098 Lines: 48 (Built this time and passed a basic sniff-test.) During allocator-intensive workloads, kswapd will be woken frequently causing free memory to oscillate between the high and min watermark. This is expected behaviour. Unfortunately, if the highest zone is small, a problem occurs. This seems to happen most with recent sandybridge laptops but it's probably a co-incidence as some of these laptops just happen to have a small Normal zone. The reproduction case is almost always during copying large files that kswapd pegs at 100% CPU until the file is deleted or cache is dropped. The problem is mostly down to sleeping_prematurely() keeping kswapd awake when the highest zone is small and unreclaimable and compounded by the fact we shrink slabs even when not shrinking zones causing a lot of time to be spent in shrinkers and a lot of memory to be reclaimed. Patch 1 corrects sleeping_prematurely to check the zones matching the classzone_idx instead of all zones. Patch 2 avoids shrinking slab when we are not shrinking a zone. Patch 3 notes that sleeping_prematurely is checking lower zones against a high classzone which is not what allocators or balance_pgdat() is doing leading to an artifical believe that kswapd should be still awake. Patch 4 notes that when balance_pgdat() gives up on a high zone that the decision is not communicated to sleeping_prematurely() This problem affects 2.6.38.8 for certain and is expected to affect 2.6.39 and 3.0-rc4 as well. If accepted, they need to go to -stable to be picked up by distros and this series is against 3.0-rc4. I've cc'd people that reported similar problems recently to see if they still suffer from the problem and if this fixes it. mm/vmscan.c | 59 +++++++++++++++++++++++++++++++++++------------------------ 1 files changed, 35 insertions(+), 24 deletions(-) -- 1.7.3.4 -- 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/