linux-kernel - Re: [PATCH 2/3] check unevictable flag in lumy reclaim v2

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Date:	Thu, 11 Jun 2009 18:39:01 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
	"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	apw@...onical.com, riel@...hat.com, mel@....ul.ie
Subject: Re: [PATCH 2/3] check unevictable flag in lumy reclaim v2

On Thu, Jun 11, 2009 at 6:37 PM, Minchan Kim<minchan.kim@...il.com> wrote:
> On Thu, Jun 11, 2009 at 5:38 PM, KAMEZAWA
> Hiroyuki<kamezawa.hiroyu@...fujitsu.com> wrote:
>> How about this ?
>>
>> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>>
>> 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 <kamezawa.hiroyu@...fujitsu.com>
>> ---
>>  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.

typo.

It seems we can remove PageUnevictable check in __isolate_lru_pages.
Sorry for noise.

> 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)
>
>                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.
>
> I am not sure this is right in case of memcg.
>
> --
> Kinds regards,
> Minchan Kim
>



-- 
Kinds regards,
Minchan Kim
--
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