linux-kernel - Re: [PATCH 1/3] mm/page_alloc: factor out setting of pcp->high and pcp->batch.

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Message-ID: <516300C7.7000008@linux.vnet.ibm.com>
Date:	Mon, 08 Apr 2013 10:39:19 -0700
From:	Cody P Schafer <cody@...ux.vnet.ibm.com>
To:	Simon Jeons <simon.jeons@...il.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Linux MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] mm/page_alloc: factor out setting of pcp->high and
 pcp->batch.

On 04/06/2013 06:37 PM, Simon Jeons wrote:
> Hi Cody,
> On 04/06/2013 04:33 AM, Cody P Schafer wrote:
>> Creates pageset_set_batch() for use in setup_pageset().
>> pageset_set_batch() imitates the functionality of
>> setup_pagelist_highmark(), but uses the boot time
>> (percpu_pagelist_fraction == 0) calculations for determining ->high
>
> Why need adjust pcp->high, pcp->batch during system running? What's the
> requirement?
>

There is currently a sysctl (which I patch later in this series) which 
allows adjusting the ->high mark (and, indirectly, ->batch). 
Additionally, memory hotplug changes ->high and ->batch due to the zone 
size changing (essentially, zone->managed_pages and zone->present_pages 
have changed) , meaning that zone_batchsize(), which is used at boot to 
set ->batch and (indirectly) ->high has a different output.

Note that in addition to the 2 users of this functionality mentioned 
here, I'm currently working on anther resizer of zones (runtime NUMA 
reconfiguration).

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