linux-kernel - Re: [RFC][PATCH] page reclaim throttle take2

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Message-ID: <47C4EF2D.90508@linux.vnet.ibm.com>
Date:	Wed, 27 Feb 2008 10:33:41 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
CC:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Rik van Riel <riel@...hat.com>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Nick Piggin <npiggin@...e.de>
Subject: Re: [RFC][PATCH] page reclaim throttle take2

KOSAKI Motohiro wrote:
> Hi
> 
>>> I don't think so.
>>> all modern many cpu machine stand on NUMA.
>>> it mean following,
>>>  - if cpu increases, then zone increases, too.
>>>
>>> if default value increase by #cpus, lock contension dramatically increase
>>> on large numa.
>>>
>>> Have I overlooked anything?
>>>
>> How about adding something like..
>> == 
>> CONFIG_SIMULTANEOUS_PAGE_RECLAIMERS 
>> int
>> default 3
>> depends on DEBUG
>> help
>>   This value determines the number of threads which can do page reclaim
>>   in a zone simultaneously. If this is too big, performance under heavy memory
>>   pressure will decrease.
>>   If unsure, use default.
>> ==
>>
>> Then, you can get performance reports from people interested in this
>> feature in test cycle.
> 
> hm, intersting.
> but sysctl parameter is more better, i think.
> 
> OK, I'll add it at next post.

I think sysctl should be interesting. The config option provides good
documentation, but it is static in nature (requires reboot to change). I wish we
could have the best of both worlds.

-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL
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