linux-kernel - Re: [PATCH] vmscan: evict use-once pages first (v2)

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Date:	Wed, 29 Apr 2009 12:18:22 -0400
From:	Rik van Riel <riel@...hat.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Elladan <elladan@...imo.com>, linux-kernel@...r.kernel.org,
	tytso@....edu, linux-mm@...ck.org
Subject: Re: [PATCH] vmscan: evict use-once pages first (v2)

KOSAKI Motohiro wrote:
> Hi
>
> Looks good than previous version. but I have one question.
>
>   
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index eac9577..4471dcb 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -1489,6 +1489,18 @@ static void shrink_zone(int priority, struct zone *zone,
>>                        nr[l] = scan;
>>        }
>>
>> +       /*
>> +        * When the system is doing streaming IO, memory pressure here
>> +        * ensures that active file pages get deactivated, until more
>> +        * than half of the file pages are on the inactive list.
>> +        *
>> +        * Once we get to that situation, protect the system's working
>> +        * set from being evicted by disabling active file page aging.
>> +        * The logic in get_scan_ratio protects anonymous pages.
>> +        */
>> +       if (nr[LRU_INACTIVE_FILE] > nr[LRU_ACTIVE_FILE])
>> +               nr[LRU_ACTIVE_FILE] = 0;
>> +
>>        while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] ||
>>                                        nr[LRU_INACTIVE_FILE]) {
>>                for_each_evictable_lru(l) {
>>     
>
> we handle active_anon vs inactive_anon ratio by shrink_list().
> Why do you insert this logic insert shrink_zone() ?
>   
Good question.  I guess that at lower priority levels, we get to scan
a lot more pages and we could go from having too many inactive
file pages to not having enough in one invocation of shrink_zone().

That makes shrink_list() the better place to implement this, even if
it means doing this comparison more often.

I'll send a new patch this afternoon.
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