From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id 042186B004A for ; Thu, 9 Sep 2010 22:57:04 -0400 (EDT) Received: from m5.gw.fujitsu.co.jp ([10.0.50.75]) by fgwmail7.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o8A2v1NI008617 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Fri, 10 Sep 2010 11:57:01 +0900 Received: from smail (m5 [127.0.0.1]) by outgoing.m5.gw.fujitsu.co.jp (Postfix) with ESMTP id E040145DE53 for ; Fri, 10 Sep 2010 11:57:00 +0900 (JST) Received: from s5.gw.fujitsu.co.jp (s5.gw.fujitsu.co.jp [10.0.50.95]) by m5.gw.fujitsu.co.jp (Postfix) with ESMTP id BF5D945DE51 for ; Fri, 10 Sep 2010 11:57:00 +0900 (JST) Received: from s5.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s5.gw.fujitsu.co.jp (Postfix) with ESMTP id 93362E08003 for ; Fri, 10 Sep 2010 11:57:00 +0900 (JST) Received: from ml14.s.css.fujitsu.com (ml14.s.css.fujitsu.com [10.249.87.104]) by s5.gw.fujitsu.co.jp (Postfix) with ESMTP id 4FE6CE08001 for ; Fri, 10 Sep 2010 11:57:00 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [PATCH 3/3] mm: page allocator: Drain per-cpu lists after direct reclaim allocation fails In-Reply-To: <20100909150558.GB340@csn.ul.ie> References: <20100909150558.GB340@csn.ul.ie> Message-Id: <20100910115503.C95E.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Date: Fri, 10 Sep 2010 11:56:59 +0900 (JST) Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: kosaki.motohiro@jp.fujitsu.com, Christoph Lameter , Andrew Morton , Linux Kernel List , linux-mm@kvack.org, Rik van Riel , Johannes Weiner , Minchan Kim , KAMEZAWA Hiroyuki List-ID: > On Thu, Sep 09, 2010 at 09:32:52AM -0500, Christoph Lameter wrote: > > On Thu, 9 Sep 2010, Mel Gorman wrote: > > > > > > This will have the effect of never sending IPIs for slab allocations since > > > > they do not do allocations for orders > PAGE_ALLOC_COSTLY_ORDER. > > > > > > > > > > The question is how severe is that? There is somewhat of an expectation > > > that the lower orders free naturally so it the IPI justified? That said, > > > our historical behaviour would have looked like > > > > > > if (!page && !drained && order) { > > > drain_all_pages(); > > > draiained = true; > > > goto retry; > > > } > > > > > > Play it safe for now and go with that? > > > > I am fine with no IPIs for order <= COSTLY. Just be aware that this is > > a change that may have some side effects. > > I made the choice consciously. I felt that if slab or slub were depending on > IPIs to make successful allocations in low-memory conditions that it would > experience varying stalls on bigger machines due to increased interrupts that > might be difficult to diagnose while not necessarily improving allocation > success rates. I also considered that if the machine is under pressure then > slab and slub may also be releasing pages of the same order and effectively > recycling their pages without depending on IPIs. +1. In these days, average numbers of CPUs are increasing. So we need to be afraid IPI storm than past. -- 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/ . Don't email: email@kvack.org