From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id 8D85E6B01AE for ; Thu, 25 Mar 2010 21:06:57 -0400 (EDT) Received: from m2.gw.fujitsu.co.jp ([10.0.50.72]) by fgwmail7.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o2Q16tLe029065 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Fri, 26 Mar 2010 10:06:55 +0900 Received: from smail (m2 [127.0.0.1]) by outgoing.m2.gw.fujitsu.co.jp (Postfix) with ESMTP id 01A7645DE4F for ; Fri, 26 Mar 2010 10:06:55 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (s2.gw.fujitsu.co.jp [10.0.50.92]) by m2.gw.fujitsu.co.jp (Postfix) with ESMTP id CDC6945DE4E for ; Fri, 26 Mar 2010 10:06:54 +0900 (JST) Received: from s2.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id B6F971DB8038 for ; Fri, 26 Mar 2010 10:06:54 +0900 (JST) Received: from ml14.s.css.fujitsu.com (ml14.s.css.fujitsu.com [10.249.87.104]) by s2.gw.fujitsu.co.jp (Postfix) with ESMTP id 5CAA6E38004 for ; Fri, 26 Mar 2010 10:06:51 +0900 (JST) Date: Fri, 26 Mar 2010 10:03:08 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [PATCH 10/11] Direct compact when a high-order allocation fails Message-Id: <20100326100308.564ebb7b.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20100325101653.GN2024@csn.ul.ie> References: <1269347146-7461-1-git-send-email-mel@csn.ul.ie> <1269347146-7461-11-git-send-email-mel@csn.ul.ie> <20100324101927.0d54f4ad.kamezawa.hiroyu@jp.fujitsu.com> <20100324114056.GE21147@csn.ul.ie> <20100325093006.cd0361e6.kamezawa.hiroyu@jp.fujitsu.com> <20100325094826.GM2024@csn.ul.ie> <20100325185021.63e16884.kamezawa.hiroyu@jp.fujitsu.com> <20100325101653.GN2024@csn.ul.ie> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: Andrew Morton , Andrea Arcangeli , Christoph Lameter , Adam Litke , Avi Kivity , David Rientjes , Minchan Kim , KOSAKI Motohiro , Rik van Riel , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Thu, 25 Mar 2010 10:16:54 +0000 Mel Gorman wrote: > On Thu, Mar 25, 2010 at 06:50:21PM +0900, KAMEZAWA Hiroyuki wrote: > > On Thu, 25 Mar 2010 09:48:26 +0000 > > Mel Gorman wrote: > > > > > > In that case, compact_finished() can't > > > > find there is a free chunk and do more work. How about using a function like > > > > free_pcppages_bulk(zone, pcp->batch, pcp); > > > > to bypass pcp list and freeing pages at once ? > > > > > > > > > > I think you mean to drain the PCP lists while compaction is happening > > > but is it justified? It's potentially a lot of IPI calls just to check > > > if compaction can finish a little earlier. If the pages on the PCP lists > > > are making that much of a difference to high-order page availability, it > > > implies that the zone is pretty full and it's likely that compaction was > > > avoided and we direct reclaimed. > > > > > Ah, sorry for my short word again. I mean draining "local" pcp list because > > a thread which run direct-compaction freed pages. IPI is not necessary and > > overkill. > > > > Ah, I see now. There are two places that pages get freed. release_freepages() > at the end of compaction when it's too late for compact_finished() to be > helped and within migration itself. Migration frees with either > free_page() or more commonly put_page() with put_page() being the most > frequently used. As free_page() is called on failure to migrate (rare), > there is little help in changing it and I'd rather not modify how > put_page() works. > > I could add a variant of drain_local_pages() that drains just the local PCP of > a given zone before compact_finished() is called. The cost would be a doubling > of the number of times zone->lock is taken to do the drain. Is it > justified? It seems overkill to me to take the zone->lock just in case > compaction can finish a little earlier. It feels like it would be adding > a guaranteed cost for a potential saving. > If you want to keep code comapct, I don't ask more. I worried about that just because memory hot-unplug were suffered by pagevec and pcp list before using MIGRATE_ISOLATE and proper lru_add_drain(). Thanks, -Kame -- 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