linux-kernel - Re: [PATCH 0/10] Reduce system disruption due to kswapd V2

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Date:	Mon, 22 Apr 2013 14:43:35 +0800
From:	Simon Jeons <simon.jeons@...il.com>
To:	Zlatko Calusic <zcalusic@...sync.net>
CC:	Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Slaby <jslaby@...e.cz>,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	dormando <dormando@...ia.net>,
	Satoru Moriya <satoru.moriya@....com>,
	Michal Hocko <mhocko@...e.cz>, Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/10] Reduce system disruption due to kswapd V2

Hi Zlatko,
On 04/22/2013 02:37 PM, Zlatko Calusic wrote:
> On 12.04.2013 22:07, Zlatko Calusic wrote:
>> On 12.04.2013 21:40, Mel Gorman wrote:
>>> On Thu, Apr 11, 2013 at 10:55:13PM +0200, Zlatko Calusic wrote:
>>>> On 09.04.2013 13:06, Mel Gorman wrote:
>>>> <SNIP>
>>>>
>>>> - The only slightly negative thing I observed is that with the patch
>>>> applied kswapd burns 10x - 20x more CPU. So instead of about 15
>>>> seconds, it has now spent more than 4 minutes on one particular
>>>> machine with a quite steady load (after about 12 days of uptime).
>>>> Admittedly, that's still nothing too alarming, but...
>>>>
>>>
>>> Would you happen to know what circumstances trigger the higher CPU
>>> usage?
>>>
>>
>> Really nothing special. The server is lightly loaded, but it does enough
>> reading from the disk so that pagecache is mostly populated and page
>> reclaiming is active. So, kswapd is no doubt using CPU time gradually,
>> nothing extraordinary.
>>
>> When I sent my reply yesterday, the server uptime was 12 days, and
>> kswapd had accumulated 4:28 CPU time. Now, approx 24 hours later (13
>> days uptime):
>>
>> root        23  0.0  0.0      0     0 ?        S    Mar30   4:52 
>> [kswapd0]
>>
>> I will apply your v3 series soon and see if there's any improvement wrt
>> CPU usage, although as I said I don't see that as a big issue. It's
>> still only 0.013% of available CPU resources (dual core CPU).
>>
>
> JFTR, v3 kswapd uses about 15% more CPU time than v2. 2:50 kswapd CPU 
> time after 6 days 14h uptime.
>
> And find attached another debugging graph that shows how ANON pages 
> are privileged in the ZONE_NORMAL on a 4GB machine. Take notice that 
> the number of pages in the ZONE_DMA32 is scaled (/5) to fit the graph 
> nicely.
>

Could you tell me how you draw this picture?

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