From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id 7CC6D8D003B for ; Mon, 16 May 2011 11:07:03 -0400 (EDT) From: Mel Gorman Subject: [PATCH 0/2] Eliminate hangs when using frequent high-order allocations V3 Date: Mon, 16 May 2011 16:06:55 +0100 Message-Id: <1305558417-24354-1-git-send-email-mgorman@suse.de> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: James Bottomley , Colin King , Raghavendra D Prabhu , Jan Kara , Chris Mason , Christoph Lameter , Pekka Enberg , Rik van Riel , Johannes Weiner , Minchan Kim , linux-fsdevel , linux-mm , linux-kernel , linux-ext4 , stable , Mel Gorman Changelog since V2 o Drop all SLUB latency-reducing patches. Changelog since V1 o kswapd should sleep if need_resched o Remove __GFP_REPEAT from GFP flags when speculatively using high orders so direct/compaction exits earlier o Remove __GFP_NORETRY for correctness o Correct logic in sleeping_prematurely o Leave SLUB using the default slub_max_order There are a few reports of people experiencing hangs when copying large amounts of data with kswapd using a large amount of CPU which appear to be due to recent reclaim changes. SLUB using high orders is the trigger but not the root cause as SLUB has been using high orders for a while. The root cause was bugs introduced into reclaim which are addressed by the following two patches. Patch 1 corrects logic introduced by commit [1741c877: mm: kswapd: keep kswapd awake for high-order allocations until a percentage of the node is balanced] to allow kswapd to go to sleep when balanced for high orders. Patch 2 notes that even when kswapd is failing to keep up with allocation requests, it should still go to sleep when its quota has expired to prevent it spinning. This version drops the patches whereby SLUB avoids expensive steps in the page allocator, reclaim and compaction due to a lack of agreement on whether it was an appropriate step or not and not being critical to resolve the hang. Chris Wood reports that these two patches in isolation are sufficient to prevent the system hanging. These should be also considered for -stable for 2.6.38. -- 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