From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with SMTP id CA6216B004D for ; Thu, 11 Jun 2009 18:54:03 -0400 (EDT) Received: by yw-out-1718.google.com with SMTP id 5so876612ywm.26 for ; Thu, 11 Jun 2009 15:55:45 -0700 (PDT) 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 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org 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 List-ID: 2009/6/11 KAMEZAWA Hiroyuki : > Minchan Kim wrote: >> 2009/6/11 KAMEZAWA Hiroyuki : >>> Minchan Kim =E3=81=95=E3=82=93 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 lum= p >>>>> 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 >>>>> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >>>>> --- 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) !=3D >>>>> zone_id)) >>>>> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?continue; >>>>> + ? ? ? ? ? ? ? ? ? ? ? /* >>>>> + ? ? ? ? ? ? ? ? ? ? ? ?* We tries to free all pages in this range t= o >>>>> create >>>>> + ? ? ? ? ? ? ? ? ? ? ? ?* a free large page. Then, if the range >>>>> includes a page >>>>> + ? ? ? ? ? ? ? ? ? ? ? ?* never be reclaimed, we have no reason to d= o >>>>> 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. >> =C2=A0 =C2=A0 =C2=A0 =C2=A0 /* >> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0* When this function is being called f= or lumpy reclaim, we >> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0* initially look into all LRU pages, a= ctive, inactive and >> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0* unevictable; only give shrink_page_l= ist evictable pages. >> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0*/ >> =C2=A0 =C2=A0 =C2=A0 =C2=A0 if (PageUnevictable(page)) >> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 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(...) > { > =C2=A0 =C2=A0 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 > > --=20 Kinds regards, Minchan Kim -- 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