From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with SMTP id BFF436B004A for ; Tue, 30 Nov 2010 21:23:15 -0500 (EST) Received: from m6.gw.fujitsu.co.jp ([10.0.50.76]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id oB12NDB4000617 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Wed, 1 Dec 2010 11:23:13 +0900 Received: from smail (m6 [127.0.0.1]) by outgoing.m6.gw.fujitsu.co.jp (Postfix) with ESMTP id E8E0745DE4F for ; Wed, 1 Dec 2010 11:23:12 +0900 (JST) Received: from s6.gw.fujitsu.co.jp (s6.gw.fujitsu.co.jp [10.0.50.96]) by m6.gw.fujitsu.co.jp (Postfix) with ESMTP id CC64945DE4C for ; Wed, 1 Dec 2010 11:23:12 +0900 (JST) Received: from s6.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s6.gw.fujitsu.co.jp (Postfix) with ESMTP id B146E1DB8014 for ; Wed, 1 Dec 2010 11:23:12 +0900 (JST) Received: from m108.s.css.fujitsu.com (m108.s.css.fujitsu.com [10.249.87.108]) by s6.gw.fujitsu.co.jp (Postfix) with ESMTP id 31A6E1DB8015 for ; Wed, 1 Dec 2010 11:23:12 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [PATCH 1/3] mm: kswapd: Stop high-order balancing when any suitable zone is balanced In-Reply-To: <1291169636.12777.43.camel@sli10-conroe> References: <1291137339-6323-2-git-send-email-mel@csn.ul.ie> <1291169636.12777.43.camel@sli10-conroe> Message-Id: <20101201112354.ABA8.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Date: Wed, 1 Dec 2010 11:23:11 +0900 (JST) Sender: owner-linux-mm@kvack.org To: Shaohua Li Cc: kosaki.motohiro@jp.fujitsu.com, Mel Gorman , Simon Kirby , Dave Hansen , linux-mm , linux-kernel List-ID: > On Wed, 2010-12-01 at 01:15 +0800, Mel Gorman wrote: > > When the allocator enters its slow path, kswapd is woken up to balance the > > node. It continues working until all zones within the node are balanced. For > > order-0 allocations, this makes perfect sense but for higher orders it can > > have unintended side-effects. If the zone sizes are imbalanced, kswapd > > may reclaim heavily on a smaller zone discarding an excessive number of > > pages. The user-visible behaviour is that kswapd is awake and reclaiming > > even though plenty of pages are free from a suitable zone. > > > > This patch alters the "balance" logic to stop kswapd if any suitable zone > > becomes balanced to reduce the number of pages it reclaims from other zones. > from my understanding, the patch will break reclaim high zone if a low > zone meets the high order allocation, even the high zone doesn't meet > the high order allocation. This, for example, will make a high order > allocation from a high zone fallback to low zone and quickly exhaust low > zone, for example DMA. This will break some drivers. Have you seen patch [3/3]? I think it migigate your pointed issue. -- 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 policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org