Re: [PATCH] memory-hotplug: fix zone stat mismatch

[Wen Congyang]

At 09/20/2012 04:17 AM, Minchan Kim Wrote:
> Hi KOSAKI,
> 
> On Wed, Sep 19, 2012 at 02:05:20PM -0400, KOSAKI Motohiro wrote:
>> On Wed, Sep 19, 2012 at 3:29 AM, Minchan Kim <minchan@xxxxxxxxxx> wrote:
>>> During memory-hotplug stress test, I found NR_ISOLATED_[ANON|FILE]
>>> are increasing so that kernel are hang out.
>>>
>>> The cause is that when we do memory-hotadd after memory-remove,
>>> __zone_pcp_update clear out zone's ZONE_STAT_ITEMS in setup_pageset
>>> without draining vm_stat_diff of all CPU.
>>>
>>> This patch fixes it.
>>
>> zone_pcp_update() is called from online pages path. but IMHO,
>> the statistics should be drained offline path. isn't it?
> 
> It isn't necessary because statistics is right until we reset it to zero
> in online path.
> Do you have something on your mind that we have to drain it in offline path?

When a node is offlined and onlined again. We create node_data[i] in the
function hotadd_new_pgdat(), and we will lost the statistics stored in
zone->pageset. So we should drain it in offline path.

Thanks
Wen Congyang

> 
>>
>> thanks.
> 

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