From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail190.messagelabs.com (mail190.messagelabs.com [216.82.249.51]) by kanga.kvack.org (Postfix) with SMTP id 5F8306B009B for ; Sun, 24 Oct 2010 23:11:18 -0400 (EDT) Received: from m5.gw.fujitsu.co.jp ([10.0.50.75]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id o9P3BFrA023354 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Mon, 25 Oct 2010 12:11:16 +0900 Received: from smail (m5 [127.0.0.1]) by outgoing.m5.gw.fujitsu.co.jp (Postfix) with ESMTP id A674645DE57 for ; Mon, 25 Oct 2010 12:11:15 +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 7D30945DE56 for ; Mon, 25 Oct 2010 12:11:15 +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 58BBA1DB8043 for ; Mon, 25 Oct 2010 12:11:15 +0900 (JST) Received: from ml13.s.css.fujitsu.com (ml13.s.css.fujitsu.com [10.249.87.103]) by s5.gw.fujitsu.co.jp (Postfix) with ESMTP id 0909C1DB803F for ; Mon, 25 Oct 2010 12:11:15 +0900 (JST) Date: Mon, 25 Oct 2010 12:05:50 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [PATCH] do_migrate_range: avoid failure as much as possible Message-Id: <20101025120550.45745c3d.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20101025025703.GA13858@localhost> References: <1287974851-4064-1-git-send-email-lliubbo@gmail.com> <20101025114017.86ee5e54.kamezawa.hiroyu@jp.fujitsu.com> <20101025025703.GA13858@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Wu Fengguang Cc: Bob Liu , "akpm@linux-foundation.org" , "linux-mm@kvack.org" , "mel@csn.ul.ie" , "kosaki.motohiro@jp.fujitsu.com" List-ID: On Mon, 25 Oct 2010 10:57:03 +0800 Wu Fengguang wrote: > On Mon, Oct 25, 2010 at 10:40:17AM +0800, KAMEZAWA Hiroyuki wrote: > > On Mon, 25 Oct 2010 10:47:31 +0800 > > Bob Liu wrote: > > > > > It's normal for isolate_lru_page() to fail at times. The failures are > > > typically temporal and may well go away when offline_pages() retries > > > the call. So it seems more reasonable to migrate as much as possible > > > to increase the chance of complete success in next retry. > > > > > > This patch remove page_count() check and remove putback_lru_pages() and > > > call migrate_pages() regardless of not_managed to reduce failure as much > > > as possible. > > > > > > Signed-off-by: Bob Liu > > > > -EBUSY should be returned. > > It does return -EBUSY when ALL pages cannot be isolated from LRU (or > is non-LRU pages at all). That means offline_pages() will repeat calls > to do_migrate_range() as fast as possible as long as it can make > progress. > I read the patch wrong ? "ret = -EBUSY" is dropped and "ret" will be 0 or just a return code of migrate_page(). > Is that behavior good enough? It does need some comment for this > non-obvious return value. > > btw, the caller side code can be simplified (no behavior change). > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index dd186c1..606d358 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -848,17 +848,13 @@ repeat: > pfn = scan_lru_pages(start_pfn, end_pfn); > if (pfn) { /* We have page on LRU */ > ret = do_migrate_range(pfn, end_pfn); > - if (!ret) { > - drain = 1; > - goto repeat; > - } else { > - if (ret < 0) > - if (--retry_max == 0) > - goto failed_removal; > + if (ret < 0) { > + if (--retry_max <= 0) > + goto failed_removal; > yield(); > - drain = 1; > - goto repeat; > } > + drain = 1; > + goto repeat; > } This changes behavior. This "ret" can be > 0 because migrate_page()'s return code is "Return: Number of pages not migrated or error code." Then, ret < 0 ===> maybe ebusy ret > 0 ===> some pages are not migrated. maybe PG_writeback or some ret == 0 ===> ok, all condition green. try next chunk soon. Then, I added "yield()" and --retrym_max for !ret cases. 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