From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta12.messagelabs.com (mail6.bemta12.messagelabs.com [216.82.250.247]) by kanga.kvack.org (Postfix) with ESMTP id D03A2900225 for ; Fri, 24 Jun 2011 09:43:22 -0400 (EDT) From: Mel Gorman Subject: [PATCH 0/4] Stop kswapd consuming 100% CPU when highest zone is small Date: Fri, 24 Jun 2011 14:43:14 +0100 Message-Id: <1308922998-15529-1-git-send-email-mgorman@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: 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 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 3.0-rc4 and 2.6.38.8 for certain and is expected to affect 2.6.39 as well. If accepted, they need to go to -stable to be picked up by distros. 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 | 57 ++++++++++++++++++++++++++++++++++----------------------- 1 files changed, 34 insertions(+), 23 deletions(-) -- 1.7.3.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org