Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756806Ab2FOMbw (ORCPT ); Fri, 15 Jun 2012 08:31:52 -0400 Received: from mail-vb0-f46.google.com ([209.85.212.46]:37099 "EHLO mail-vb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756725Ab2FOMbv convert rfc822-to-8bit (ORCPT ); Fri, 15 Jun 2012 08:31:51 -0400 MIME-Version: 1.0 In-Reply-To: <4FDAE3CC.60801@kernel.org> References: <1339661592-3915-1-git-send-email-kosaki.motohiro@gmail.com> <20120614145716.GA2097@barrios> <4FDAE3CC.60801@kernel.org> Date: Fri, 15 Jun 2012 20:31:50 +0800 Message-ID: Subject: Re: [resend][PATCH] mm, vmscan: fix do_try_to_free_pages() livelock From: Hillf Danton To: Minchan Kim Cc: KOSAKI Motohiro , linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, Nick Piggin , Michal Hocko , Johannes Weiner , Mel Gorman , KAMEZAWA Hiroyuki Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2806 Lines: 70 Hi Minchan and KOSAKI On Fri, Jun 15, 2012 at 3:27 PM, Minchan Kim wrote: > On 06/15/2012 01:10 AM, KOSAKI Motohiro wrote: > >> On Thu, Jun 14, 2012 at 10:57 AM, Minchan Kim wrote: >>> Hi KOSAKI, >>> >>> Sorry for late response. >>> Let me ask a question about description. >>> >>> On Thu, Jun 14, 2012 at 04:13:12AM -0400, 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. >>> >>> I have tried imagined scenario you mentioned above with code level but >>> unfortunately I got failed. >>> If kswapd can't meet high watermark on order-0, it doesn't sleep if I don't miss something. >> >> pgdat_balanced() doesn't recognized zone. Therefore kswapd may sleep >> if node has multiple zones. Hm ok, I realized my descriptions was >> slightly misleading. priority 0 is not needed. bakance_pddat() calls >> pgdat_balanced() >> every priority. Most easy case is, movable zone has a lot of free pages and >> normal zone has no reclaimable page. >> >> btw, current pgdat_balanced() logic seems not correct. kswapd should >> sleep only if every zones have much free pages than high water mark >> _and_ 25% of present pages in node are free. >> > > > Sorry. I can't understand your point. > Current kswapd doesn't sleep if relevant zones don't have free pages above high watermark. > It seems I am missing your point. > Please anybody correct me. > Who left comment on unreclaimable there, and why? /* * balance_pgdat() skips over all_unreclaimable after * DEF_PRIORITY. Effectively, it considers them balanced so * they must be considered balanced here as well if kswapd * is to sleep */ BTW, are you still using prefetch_prev_lru_page? Good Weekend Hillf -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/