linux-kernel - Re: [PATCH 01/10] mm: vmscan: Limit the number of pages kswapd reclaims at each priority

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <514BE54C.4050106@gmail.com>
Date:	Fri, 22 Mar 2013 12:59:56 +0800
From:	Will Huck <will.huckk@...il.com>
To:	Rik van Riel <riel@...hat.com>
CC:	Johannes Weiner <hannes@...xchg.org>, Mel Gorman <mgorman@...e.de>,
	Linux-MM <linux-mm@...ck.org>, Jiri Slaby <jslaby@...e.cz>,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	Zlatko Calusic <zcalusic@...sync.net>,
	dormando <dormando@...ia.net>,
	Satoru Moriya <satoru.moriya@....com>,
	Michal Hocko <mhocko@...e.cz>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 01/10] mm: vmscan: Limit the number of pages kswapd reclaims
 at each priority

Hi Rik,
On 03/22/2013 11:56 AM, Will Huck wrote:
> Hi Rik,
> On 03/22/2013 11:52 AM, Rik van Riel wrote:
>> On 03/21/2013 08:05 PM, Will Huck wrote:
>>
>>> One offline question, how to understand this in function balance_pgdat:
>>> /*
>>>   * Do some background aging of the anon list, to give
>>>   * pages a chance to be referenced before reclaiming.
>>>   */
>>> age_acitve_anon(zone, &sc);
>>
>> The anon lrus use a two-handed clock algorithm. New anonymous pages
>> start off on the active anon list. Older anonymous pages get moved
>> to the inactive anon list.
>
> The file lrus also use the two-handed clock algorithm, correct?

After reinvestigate the codes, the answer is no. But why have this 
difference? I think you are the expert for this question, expect your 
explanation. :-)

>
>>
>> If they get referenced before they reach the end of the inactive anon
>> list, they get moved back to the active list.
>>
>> If we need to swap something out and find a non-referenced page at the
>> end of the inactive anon list, we will swap it out.
>>
>> In order to make good pageout decisions, pages need to stay on the
>> inactive anon list for a longer time, so they have plenty of time to
>> get referenced, before the reclaim code looks at them.
>>
>> To achieve that, we will move some active anon pages to the inactive
>> anon list even when we do not want to swap anything out - as long as
>> the inactive anon list is below its target size.
>>
>> Does that make sense?
>
> Make sense, thanks.
>

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/