linux-kernel - Re: [patch 0/3] mm: improve page aging fairness between zones/nodes

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Date:	Wed, 24 Jul 2013 20:46:42 +0800
From:	Hush Bensen <hush.bensen@...il.com>
To:	Zlatko Calusic <zcalusic@...sync.net>,
	Johannes Weiner <hannes@...xchg.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Andrea Arcangeli <aarcange@...hat.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 0/3] mm: improve page aging fairness between zones/nodes

于 2013/7/24 19:18, Zlatko Calusic 写道:
> On 22.07.2013 18:48, Zlatko Calusic wrote:
>> On 19.07.2013 22:55, Johannes Weiner wrote:
>>> The way the page allocator interacts with kswapd creates aging
>>> imbalances, where the amount of time a userspace page gets in memory
>>> under reclaim pressure is dependent on which zone, which node the
>>> allocator took the page frame from.
>>>
>>> #1 fixes missed kswapd wakeups on NUMA systems, which lead to some
>>> nodes falling behind for a full reclaim cycle relative to the other
>>> nodes in the system
>>>
>>> #3 fixes an interaction where kswapd and a continuous stream of page
>>> allocations keep the preferred zone of a task between the high and
>>> low watermark (allocations succeed + kswapd does not go to sleep)
>>> indefinitely, completely underutilizing the lower zones and
>>> thrashing on the preferred zone
>>>
>>> These patches are the aging fairness part of the thrash-detection
>>> based file LRU balancing. Andrea recommended to submit them
>>> separately as they are bugfixes in their own right.
>>>
>>
>> I have the patch applied and under testing. So far, so good. It looks
>> like it could finally fix the bug that I was chasing few months ago
>> (nicely described in your bullet #3). But, few more days of testing will
>> be needed before I can reach a quality verdict.
>>
>
> Well, only 2 days later it's already obvious that the patch is 
> perfect! :)
>
> In the attached image, in the left column are the graphs covering last 
> day and a half. It can be observed that zones are really balanced, and 
> that aging is practically perfect. Graphs on the right column cover 
> last 10 day period, and the left side of the upper graph shows how it 
> would look with the stock kernel after about 20 day uptime (although 
> only a few days is enough to reach such imbalance). File pages in the 
> Normal zone are extinct species (red) and the zone is choke full of 
> anon pages (blue). Having seen a lot of this graphs, I'm certain that 
> it won't happen anymore with your patch applied. The balance is 
> restored! Thank you for your work. Feel free to add:
>
> Tested-by: Zlatko Calusic <zcalusic@...sync.net>

Thanks for your testing Zlatko, could you tell me which benchmark or 
workload you are using? Btw, which tool is used to draw these nice 
pictures? ;-)

>
> Regards,

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