From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id 1D64B6B004F for ; Sun, 12 Jul 2009 22:58:08 -0400 (EDT) Date: Mon, 13 Jul 2009 11:18:01 +0800 From: Shaohua Li Subject: Re: [PATCH] switch free memory back to MIGRATE_MOVABLE Message-ID: <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090713120549.6252.A69D9226@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: KAMEZAWA Hiroyuki , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "mel@csn.ul.ie" , "akpm@linux-foundation.org" List-ID: 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. Thanks, Shaohua -- 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