From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763222AbZFKLT7 (ORCPT ); Thu, 11 Jun 2009 07:19:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761825AbZFKLTv (ORCPT ); Thu, 11 Jun 2009 07:19:51 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:60244 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757681AbZFKLTu (ORCPT ); Thu, 11 Jun 2009 07:19:50 -0400 Message-ID: <9d4a7c0691aa5e13247f694f2dfe55ad.squirrel@webmail-b.css.fujitsu.com> In-Reply-To: <28c262360906110237u1f3d1877hae54a51575955549@mail.gmail.com> References: <20090611165535.cf46bf29.kamezawa.hiroyu@jp.fujitsu.com> <20090611170152.7a43b13b.kamezawa.hiroyu@jp.fujitsu.com> <20090611172249.6D3C.A69D9226@jp.fujitsu.com> <20090611173819.0f76e431.kamezawa.hiroyu@jp.fujitsu.com> <28c262360906110237u1f3d1877hae54a51575955549@mail.gmail.com> Date: Thu, 11 Jun 2009 20:19:45 +0900 (JST) Subject: Re: [PATCH 2/3] check unevictable flag in lumy reclaim v2 From: "KAMEZAWA Hiroyuki" To: "Minchan Kim" Cc: "KAMEZAWA Hiroyuki" , "KOSAKI Motohiro" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "nishimura@mxp.nes.nec.co.jp" , "balbir@linux.vnet.ibm.com" , "akpm@linux-foundation.org" , apw@canonical.com, riel@redhat.com, mel@csn.ul.ie User-Agent: SquirrelMail/1.4.16 MIME-Version: 1.0 Content-Type: text/plain;charset=iso-2022-jp Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) Importance: Normal Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Minchan Kim さん wrote: > On Thu, Jun 11, 2009 at 5:38 PM, KAMEZAWA > Hiroyuki wrote: >> How about this ? >> >> From: KAMEZAWA Hiroyuki >> >> Lumpy reclaim check pages from their pfn. Then, it can find unevictable >> pages >> in its loop. >> Abort lumpy reclaim when we find Unevictable page, we never get a lump >> of pages for requested order. >> >> Changelog: v1->v2 >> ?- rewrote commet. >> >> Signed-off-by: KAMEZAWA Hiroyuki >> --- >> ?mm/vmscan.c | ? ?9 +++++++++ >> ?1 file changed, 9 insertions(+) >> >> Index: lumpy-reclaim-trial/mm/vmscan.c >> =================================================================== >> --- lumpy-reclaim-trial.orig/mm/vmscan.c >> +++ lumpy-reclaim-trial/mm/vmscan.c >> @@ -936,6 +936,15 @@ static unsigned long isolate_lru_pages(u >> ? ? ? ? ? ? ? ? ? ? ? ?/* Check that we have not crossed a zone >> boundary. */ >> ? ? ? ? ? ? ? ? ? ? ? ?if (unlikely(page_zone_id(cursor_page) != >> zone_id)) >> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?continue; >> + ? ? ? ? ? ? ? ? ? ? ? /* >> + ? ? ? ? ? ? ? ? ? ? ? ?* We tries to free all pages in this range to >> create >> + ? ? ? ? ? ? ? ? ? ? ? ?* a free large page. Then, if the range >> includes a page >> + ? ? ? ? ? ? ? ? ? ? ? ?* never be reclaimed, we have no reason to do >> more. >> + ? ? ? ? ? ? ? ? ? ? ? ?* PageUnevictable page is not a page which can >> be >> + ? ? ? ? ? ? ? ? ? ? ? ?* easily freed. Abort this scan now. >> + ? ? ? ? ? ? ? ? ? ? ? ?*/ >> + ? ? ? ? ? ? ? ? ? ? ? if (unlikely(PageUnevictable(cursor_page))) >> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? break; > > __isolate_lru_pages already checked PageUnevictable to return error. > I want to remove repeated check although it is trivial. > > By your patch, It seems to remove PageUnevictable check in > __isolate_lru_pages. > yes. > But I know that. If we remove PageUnevictable check in > __isolate_lru_pages, it can't go into BUG in non-lumpy case. ( I > mentioned following as code) > In non-lumpy case, we'll never see Unevictable, maybe. > case -EBUSY: > /* else it is being freed elsewhere */ > list_move(&page->lru, src); > continue; > > default: > BUG(); > } > > > It means we can remove BUG in non-lumpy case and then add BUG into > __isolate_lru_pages directly. > > If we can do it, we can remove unnecessary PageUnevictable check in > __isolate_lru_page. > Hmm, but Unevicable check had tons of troubles at its implementation and I don't want to do it at once. > I am not sure this is right in case of memcg. > I think we don't see Unevictable in memcg's path if my memcg-lru code works as designed. I'll postpone this patch for a while until my brain works well. Thanks, -Kame