From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx148.postini.com [74.125.245.148]) by kanga.kvack.org (Postfix) with SMTP id A54646B006C for ; Thu, 14 Jun 2012 04:54:37 -0400 (EDT) Received: from m1.gw.fujitsu.co.jp (unknown [10.0.50.71]) by fgwmail5.fujitsu.co.jp (Postfix) with ESMTP id AB1053EE0BC for ; Thu, 14 Jun 2012 17:54:35 +0900 (JST) Received: from smail (m1 [127.0.0.1]) by outgoing.m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 8F24745DE55 for ; Thu, 14 Jun 2012 17:54:35 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (s1.gw.fujitsu.co.jp [10.0.50.91]) by m1.gw.fujitsu.co.jp (Postfix) with ESMTP id 7765645DE58 for ; Thu, 14 Jun 2012 17:54:35 +0900 (JST) Received: from s1.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id 679E91DB803C for ; Thu, 14 Jun 2012 17:54:35 +0900 (JST) Received: from m107.s.css.fujitsu.com (m107.s.css.fujitsu.com [10.240.81.147]) by s1.gw.fujitsu.co.jp (Postfix) with ESMTP id 1CE5B1DB8043 for ; Thu, 14 Jun 2012 17:54:35 +0900 (JST) Message-ID: <4FD9A625.1050300@jp.fujitsu.com> Date: Thu, 14 Jun 2012 17:51:49 +0900 From: Kamezawa Hiroyuki MIME-Version: 1.0 Subject: Re: [resend][PATCH] mm, vmscan: fix do_try_to_free_pages() livelock References: <1339661592-3915-1-git-send-email-kosaki.motohiro@gmail.com> In-Reply-To: <1339661592-3915-1-git-send-email-kosaki.motohiro@gmail.com> Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: kosaki.motohiro@gmail.com Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, KOSAKI Motohiro , Nick Piggin , Michal Hocko , Johannes Weiner , Mel Gorman , Minchan Kim (2012/06/14 17:13), kosaki.motohiro@gmail.com wrote: > From: KOSAKI Motohiro > > Currently, do_try_to_free_pages() can enter livelock. Because of, > now vmscan has two conflicted policies. > > 1) kswapd sleep when it couldn't reclaim any page when reaching > priority 0. This is because to avoid kswapd() infinite > loop. That said, kswapd assume direct reclaim makes enough > free pages to use either regular page reclaim or oom-killer. > This logic makes kswapd -> direct-reclaim dependency. > 2) direct reclaim continue to reclaim without oom-killer until > kswapd turn on zone->all_unreclaimble. This is because > to avoid too early oom-kill. > This logic makes direct-reclaim -> kswapd dependency. > > In worst case, direct-reclaim may continue to page reclaim forever > when kswapd sleeps forever. > > We can't turn on zone->all_unreclaimable from direct reclaim path > because direct reclaim path don't take any lock and this way is racy. > > Thus this patch removes zone->all_unreclaimable field completely and > recalculates zone reclaimable state every time. > > Note: we can't take the idea that direct-reclaim see zone->pages_scanned > directly and kswapd continue to use zone->all_unreclaimable. Because, it > is racy. commit 929bea7c71 (vmscan: all_unreclaimable() use > zone->all_unreclaimable as a name) describes the detail. > > Reported-by: Aaditya Kumar > Reported-by: Ying Han > Cc: Nick Piggin > Acked-by: Rik van Riel > Cc: Michal Hocko > Cc: Johannes Weiner > Cc: Mel Gorman > Cc: KAMEZAWA Hiroyuki > Cc: Minchan Kim > Signed-off-by: KOSAKI Motohiro I like this. Acked-by: KAMEZAWA Hiroyuki -- 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