From: Simon Jeons <simon.jeons@gmail.com>
To: Zheng Liu <gnehzuil.liu@gmail.com>
Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>,
linux-mm@kvack.org, muming.wq@taobao.com
Subject: Re: [question] call mark_page_accessed() in minor fault
Date: Sat, 27 Apr 2013 15:40:13 +0800 [thread overview]
Message-ID: <517B80DD.7010008@gmail.com> (raw)
In-Reply-To: <20130427075516.GA31442@gmail.com>
Hi Zheng,
On 04/27/2013 03:55 PM, Zheng Liu wrote:
> On Sat, Apr 27, 2013 at 03:10:30PM +0800, Simon Jeons wrote:
>> Hi Zheng,
>> On 04/23/2013 09:49 PM, Zheng Liu wrote:
>>> Hi Konstantin,
>>>
>>> On Tue, Apr 23, 2013 at 05:02:34PM +0400, Konstantin Khlebnikov wrote:
>>>> Zheng Liu wrote:
>>>>> Hi all,
>>>>>
>>>>> Recently we meet a performance regression about mmaped page. When we upgrade
>>>>> our product system from 2.6.18 kernel to a latest kernel, such as 2.6.32 kernel,
>>>>> we will find that mmaped pages are reclaimed very quickly. We found that when
>>>>> we hit a minor fault mark_page_accessed() is called in 2.6.18 kernel, but in
>>>>> 2.6.32 kernel we don't call mark_page_accesed(). This means that mmaped pages
>>>>> in 2.6.18 kernel are activated and moved into active list. While in 2.6.32
>>>>> kernel mmaped pages are still kept in inactive list.
>>>>>
>>>>> So my question is why we call mark_page_accessed() in 2.6.18 kernel, but don't
>>>>> call it in 2.6.32 kernel. Has any reason here?
>>>> Behavior was changed in commit
>>>> v2.6.28-6130-gbf3f3bc "mm: don't mark_page_accessed in fault path"
>>> Thanks for pointing it out.
>>>
>>>> Please see also commits
>>>> v3.2-4876-g34dbc67 "vmscan: promote shared file mapped pages" and
>>> Yes, I will give it try. If I understand correctly, this commit is
>>> useful for multi-processes program that access a shared mmaped page,
>>> but that could not be useful for us because our program is multi-thread.
>> What's the difference behavior between multi-processes and
>> multi-thread in this case?
> Hi Simon,
>
> Sorry, I am not a MM expert. IIUC, if we have two processes, this
> mmaped page will be moved into active list. But if we only have two
> threads, reference_ptes == 1, and this mmaped page won't be moved into
> active list. Finally this page could be evicted. Am I missing
> something?
Multi-threads will have same mm_struct and task_struct?
>
> Thanks,
> - Zheng
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next prev parent reply other threads:[~2013-04-27 7:40 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-23 12:25 [question] call mark_page_accessed() in minor fault Zheng Liu
2013-04-23 13:02 ` Konstantin Khlebnikov
2013-04-23 13:49 ` Zheng Liu
2013-04-27 7:10 ` Simon Jeons
2013-04-27 7:55 ` Zheng Liu
2013-04-27 7:40 ` Simon Jeons [this message]
2013-04-27 11:14 ` Zheng Liu
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