From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761384AbZFKWzu (ORCPT ); Thu, 11 Jun 2009 18:55:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753358AbZFKWzn (ORCPT ); Thu, 11 Jun 2009 18:55:43 -0400 Received: from mail-gx0-f214.google.com ([209.85.217.214]:60462 "EHLO mail-gx0-f214.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755068AbZFKWzm convert rfc822-to-8bit (ORCPT ); Thu, 11 Jun 2009 18:55:42 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=BytrSfvNAytHQ3htuC6TDBb3ts26b2OzrQSe3duffFDJNQA84NZz6xOxSc1sknTAlw 0vfXO00grIikjiKf+Y6YAghGqvA3OElMVpZA8Ka5OMeBWgvo07Ap++fnGqmfC8bnh5Ya 5MZtGxutdE0Pv5ND1CoB11IvAXpTg1eYx7Ze0= MIME-Version: 1.0 In-Reply-To: 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> <9d4a7c0691aa5e13247f694f2dfe55ad.squirrel@webmail-b.css.fujitsu.com> <28c262360906110459s923d7a6p4e555344e8bbd265@mail.gmail.com> Date: Fri, 12 Jun 2009 07:55:44 +0900 Message-ID: <28c262360906111555p19ca20b1m2785abddb41678dc@mail.gmail.com> Subject: Re: [PATCH 2/3] check unevictable flag in lumy reclaim v2 From: Minchan Kim To: KAMEZAWA Hiroyuki Cc: 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, Lee Schermerhorn 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 2009/6/11 KAMEZAWA Hiroyuki : > Minchan Kim wrote: >> 2009/6/11 KAMEZAWA Hiroyuki : >>> 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. >> >> I think so if it doesn't happen RAM failure. >> AFAIK, Unevictable check didn't related with RAM failure. >> >>> >>>> ? ? ? ? ? ? ? ? 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 think it's not a big problem. >> As comment said, the check's goal is to prevent in lumpy case. >>         /* >>          * When this function is being called for lumpy reclaim, we >>          * initially look into all LRU pages, active, inactive and >>          * unevictable; only give shrink_page_list evictable pages. >>          */ >>         if (PageUnevictable(page)) >>                 return ret; >> >> So I think we can remove this check. >> > agreed. > >>>> 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. >> >> If you have a concern about that, how about this ? >> (This code will be hunk since gmail webserver always mangle. Pz,forgive >> me) >> Also, we can CC original authors. >> > I'll schedule this optimization/clean up for unevictable case in queue. > Thank you for inputs. > > But it's now merge-window, I'd like to push bugfix first.(1/3 and 3/3) I agree. It's more important now. > I'd like to scheule Unevictable case fix after rc1(when mmotm stack seems > to be pushed out to Linus.) > And I'll add > int __isolate_lru_page(...) > { >     VM_BUG_ON(PageUnevictable(page)); > } > as sanity check for mmotm test time. > > Thank you for all your help. I also thanks you for considering my comment. You may add my review sign. :) Reviewed-by: Minchan Kim > -Kame > > -- Kinds regards, Minchan Kim