From: Minchan Kim <minchan.kim@gmail.com>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: linux-mm <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Yasunori Goto <y-goto@jp.fujitsu.com>,
Rik van Riel <riel@redhat.com>,
Johannes Weiner <hannes@cmpxchg.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Mel Gorman <mel@csn.ul.ie>, Christoph Lameter <cl@linux.com>
Subject: Re: [PATCH 3/3] mm, mem-hotplug: update pcp->stat_threshold when memory hotplug occur
Date: Tue, 12 Apr 2011 19:12:02 +0900 [thread overview]
Message-ID: <BANLkTinORojJgOdHeRMLMkKGc-Jitu-unQ@mail.gmail.com> (raw)
In-Reply-To: <20110412183010.B52A.A69D9226@jp.fujitsu.com>
On Tue, Apr 12, 2011 at 6:29 PM, KOSAKI Motohiro
<kosaki.motohiro@jp.fujitsu.com> wrote:
> Hi
>
>> Hi, KOSAKI
>>
>> On Mon, Apr 11, 2011 at 5:01 PM, KOSAKI Motohiro
>> <kosaki.motohiro@jp.fujitsu.com> wrote:
>> > Currently, cpu hotplug updates pcp->stat_threashold, but memory
>> > hotplug doesn't. there is no reason.
>> >
>> > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>> > Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>> > Acked-by: Mel Gorman <mel@csn.ul.ie>
>> > Acked-by: Christoph Lameter <cl@linux.com>
>>
>> I can think it makes sense so I don't oppose the patch merging.
>> But as you know I am very keen on the description.
>>
>> What is the problem if hotplug doesn't do it?
>> I means the patch solves what's problem?
>>
>> Please write down fully for better description.
>> Thanks.
>
> No real world issue. I found the fault by code review.
I don't mean we should solve only real world issue.
Just finding out code review is much valuable. :)
> No good stat_threshold might makes performance hurt.
Yes. That's I want it.
My intention is that if you write down log fully, it can help much
newbies to understand the patch in future and it would be very clear
Andrew to merge it.
What I want is following as.
==
Currently, memory hotplug doesn't updates pcp->stat_threashold.
Then, It ends up making the wrong stat_threshold and percpu_driftmark.
It could make confusing zoneinfo or overhead by frequent draining.
Even when memory is low and kswapd is awake, it can mismatch between
the number of real free pages and vmstat NR_FREE_PAGES so that it can
result in the livelock. Please look at aa4548403 for more.
This patch solves the issue.
==
--
Kind regards,
Minchan Kim
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next prev parent reply other threads:[~2011-04-12 10:12 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-11 7:59 [patch 0/3 resend] mm, mem-hotplug: proper maintainance zone attribute when memory hotplug occur KOSAKI Motohiro
2011-04-11 8:00 ` [PATCH 1/3] mm, mem-hotplug: fix section mismatch. setup_per_zone_inactive_ratio() should be __meminit KOSAKI Motohiro
2011-04-12 6:18 ` Minchan Kim
2011-04-12 10:28 ` KOSAKI Motohiro
2011-04-12 10:32 ` Minchan Kim
2011-04-12 6:38 ` KAMEZAWA Hiroyuki
2011-04-11 8:00 ` [PATCH 2/3] mm, mem-hotplug: recalculate lowmem_reserve when memory hotplug occur KOSAKI Motohiro
2011-04-12 7:03 ` Minchan Kim
2011-04-11 8:01 ` [PATCH 3/3] mm, mem-hotplug: update pcp->stat_threshold " KOSAKI Motohiro
2011-04-12 9:24 ` Minchan Kim
2011-04-12 9:29 ` KOSAKI Motohiro
2011-04-12 10:12 ` Minchan Kim [this message]
2011-04-12 10:34 ` KOSAKI Motohiro
2011-04-12 10:42 ` Minchan Kim
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