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 8A27E6B004F for ; Mon, 13 Jul 2009 01:20:21 -0400 (EDT) Received: from m3.gw.fujitsu.co.jp ([10.0.50.73]) by fgwmail5.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id n6D5exRS015049 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Mon, 13 Jul 2009 14:41:02 +0900 Received: from smail (m3 [127.0.0.1]) by outgoing.m3.gw.fujitsu.co.jp (Postfix) with ESMTP id B94EA45DE4F for ; Mon, 13 Jul 2009 14:40:59 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (s3.gw.fujitsu.co.jp [10.0.50.93]) by m3.gw.fujitsu.co.jp (Postfix) with ESMTP id 632AF45DE51 for ; Mon, 13 Jul 2009 14:40:59 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id D06241DB8041 for ; Mon, 13 Jul 2009 14:40:58 +0900 (JST) Received: from m108.s.css.fujitsu.com (m108.s.css.fujitsu.com [10.249.87.108]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id E5D561DB8042 for ; Mon, 13 Jul 2009 14:40:57 +0900 (JST) Date: Mon, 13 Jul 2009 14:38:57 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [PATCH] switch free memory back to MIGRATE_MOVABLE Message-Id: <20090713143857.07e81cb1.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20090713031801.GA4778@sli10-desk.sh.intel.com> References: <20090713115803.b78a4f4f.kamezawa.hiroyu@jp.fujitsu.com> <20090713030444.GA2582@sli10-desk.sh.intel.com> <20090713120549.6252.A69D9226@jp.fujitsu.com> <20090713031801.GA4778@sli10-desk.sh.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Shaohua Li Cc: KOSAKI Motohiro , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "mel@csn.ul.ie" , "akpm@linux-foundation.org" List-ID: On Mon, 13 Jul 2009 11:18:01 +0800 Shaohua Li wrote: > On Mon, Jul 13, 2009 at 11:08:14AM +0800, KOSAKI Motohiro wrote: > > > On Mon, Jul 13, 2009 at 10:58:03AM +0800, KAMEZAWA Hiroyuki wrote: > > > > On Mon, 13 Jul 2009 11:47:46 +0900 (JST) > > > > KOSAKI Motohiro wrote: > > > > > > > > > > When page is back to buddy and its order is bigger than pageblock_order, we can > > > > > > switch its type to MIGRATE_MOVABLE. This can reduce fragmentation. The patch > > > > > > has obvious effect when read a block device and then drop caches. > > > > > > > > > > > > Signed-off-by: Shaohua Li > > > > > > > > > > This patch change hot path, but there is no performance mesurement description. > > > > > Also, I don't like modification buddy core for only drop caches. > > > > > > > > > Li, does this patch imply fallback of migration type doesn't work well ? > > > > What is the bad case ? > > > The page is initialized as migrate_movable, and then switch to reclaimable or > > > something else when fallback occurs, but its type remains even the page gets > > > freed. When the page gets freed, its type actually can be switch back to movable, > > > this is what the patch does. > > > > This answer is not actual answer. > > Why do you think __rmqueue_fallback() doesn't works well? Do you have > > any test-case or found a bug by review? > I never said __rmqueue_fallback() doesn't work well. The page is already freed, switching > back the pageblock to movable might make next page allocation (non-movable) skip this > pageblock. So this could potentially reduce fragmentation and improve memory offline. > But your guys are right, I have no number if this will impact performance. > If this is for memory offlining, plz mention that at first ;) IIUC, if this can be a problem, fixing memory offline itself is better. No ? At implementing memory unplug, I had no problems because I assumes ZONE_MOVABLE. But ok, I welcome enhances to memory unplug. If this part is bad for you. 4714 /* 4715 * In future, more migrate types will be able to be isolation target. 4716 */ 4717 if (get_pageblock_migratetype(page) != MIGRATE_MOVABLE) 4718 goto out; plz fix this to do more precise work for zid != ZONE_MOVABLE zones. As I wrote in comments. My codes assumes ZONE_MOVABLE in many parts because I want 100%-success memory offline. 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