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 B15C66B0089 for ; Sun, 24 Oct 2010 22:57:06 -0400 (EDT) Date: Mon, 25 Oct 2010 10:57:03 +0800 From: Wu Fengguang Subject: Re: [PATCH] do_migrate_range: avoid failure as much as possible Message-ID: <20101025025703.GA13858@localhost> References: <1287974851-4064-1-git-send-email-lliubbo@gmail.com> <20101025114017.86ee5e54.kamezawa.hiroyu@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20101025114017.86ee5e54.kamezawa.hiroyu@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org To: KAMEZAWA Hiroyuki Cc: Bob Liu , "akpm@linux-foundation.org" , "linux-mm@kvack.org" , "mel@csn.ul.ie" , "kosaki.motohiro@jp.fujitsu.com" List-ID: 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. 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; } /* drain all zone's lru pagevec, this is asyncronous... */ lru_add_drain_all(); Thanks, Fengguang > > --- > > mm/memory_hotplug.c | 12 ------------ > > 1 files changed, 0 insertions(+), 12 deletions(-) > > > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > > index a4cfcdc..b64cc9b 100644 > > --- a/mm/memory_hotplug.c > > +++ b/mm/memory_hotplug.c > > @@ -687,7 +687,6 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) > > unsigned long pfn; > > struct page *page; > > int move_pages = NR_OFFLINE_AT_ONCE_PAGES; > > - int not_managed = 0; > > int ret = 0; > > LIST_HEAD(source); > > > > @@ -709,10 +708,6 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) > > page_is_file_cache(page)); > > > > } else { > > - /* Becasue we don't have big zone->lock. we should > > - check this again here. */ > > - if (page_count(page)) > > - not_managed++; > > #ifdef CONFIG_DEBUG_VM > > printk(KERN_ALERT "removing pfn %lx from LRU failed\n", > > pfn); > > @@ -720,13 +715,6 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) > > #endif > > } > > } > > - ret = -EBUSY; > > - if (not_managed) { > > - if (!list_empty(&source)) > > - putback_lru_pages(&source); > > - goto out; > > - } > > - ret = 0; > > if (list_empty(&source)) > > goto out; > > /* this function returns # of failed pages */ > > -- > > 1.6.3.3 > > > > -- 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