linux-kernel - Re: [PATCH 2/2] Filter unevictable page out in deactivate

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Message-ID: <BANLkTika5G_7Z8t-ED4RcYfKoYpLnZsjSg@mail.gmail.com>
Date:	Tue, 3 May 2011 09:29:59 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	Ying Han <yinghan@...gle.com>
Subject: Re: [PATCH 2/2] Filter unevictable page out in deactivate_page

Hi KOSAKI,

On Mon, May 2, 2011 at 7:37 PM, KOSAKI Motohiro
<kosaki.motohiro@...fujitsu.com> wrote:
>> It's pointless that deactive_page's pagevec operation about
>> unevictable page as it's nop.
>> This patch removes unnecessary overhead which might be a bit problem
>> in case that there are many unevictable page in system(ex, mprotect workload)
>>
>> Signed-off-by: Minchan Kim <minchan.kim@...il.com>
>> ---
>>  mm/swap.c |    9 +++++++++
>>  1 files changed, 9 insertions(+), 0 deletions(-)
>>
>> diff --git a/mm/swap.c b/mm/swap.c
>> index 2e9656d..b707694 100644
>> --- a/mm/swap.c
>> +++ b/mm/swap.c
>> @@ -511,6 +511,15 @@ static void drain_cpu_pagevecs(int cpu)
>>   */
>>  void deactivate_page(struct page *page)
>>  {
>> +
>> +     /*
>> +      * In workload which system has many unevictable page(ex, mprotect),
>> +      * unevictalge page deactivation for accelerating reclaim
>> +      * is pointless.
>> +      */
>> +     if (PageUnevictable(page))
>> +             return;
>> +
>
>        Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
>

Thanks!

>
> btw, I think we should check PageLRU too.
>

Yes. I remember you advised it when we push this patch but I didn't.
That's because I think most of pages in such context would be LRU as
they are cached pages.
So IMO, PageLRU checking in deactivate_page couldn't help much.


-- 
Kind regards,
Minchan Kim
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