From: Minchan Kim <minchan@kernel.org>
To: Wen Congyang <wency@cn.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>,
Shaohua Li <shli@fusionio.com>
Subject: Re: [PATCH] memory-hotplug: fix zone stat mismatch
Date: Thu, 20 Sep 2012 11:30:53 +0900 [thread overview]
Message-ID: <20120920023053.GD13234@bbox> (raw)
In-Reply-To: <505A6EB7.5070305@cn.fujitsu.com>
On Thu, Sep 20, 2012 at 09:17:43AM +0800, Wen Congyang wrote:
> 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@kernel.org> 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
I would like to clarify your word.
Create or recreate?
Why I have a question is as I look over the source code, hotadd_new_pgdat
seem to be called if we do hotadd *new* memory. It's not the case for
offline and online again you mentioned. If you're right, I should find
arch_free_nodedata to free pgdat when node is disappear but I can't find it.
Do I miss something?
> function hotadd_new_pgdat(), and we will lost the statistics stored in
> zone->pageset. So we should drain it in offline path.
Even we drain in offline patch, it still has a problem.
1. offline
2. drain -> OKAY
3. schedule
4. Process A increase zone stat
5. Process B increase zone stat
6. online
7. reset it -> we ends up lost zone stat counter which is modified between 2-6
>
> Thanks
> Wen Congyang
>
> >
> >>
> >> thanks.
> >
>
> --
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--
Kind regards,
Minchan Kim
--
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next prev parent reply other threads:[~2012-09-20 2:28 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-19 7:29 Minchan Kim
2012-09-19 18:05 ` KOSAKI Motohiro
2012-09-19 20:17 ` Minchan Kim
2012-09-20 1:17 ` Wen Congyang
2012-09-20 2:30 ` Minchan Kim [this message]
2012-09-20 3:12 ` Wen Congyang
2012-09-20 5:16 ` Minchan Kim
2012-09-20 5:22 ` Wen Congyang
2012-09-20 5:32 ` Wen Congyang
2012-09-20 5:55 ` Minchan Kim
2012-09-20 6:17 ` Wen Congyang
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