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From: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
To: Minchan Kim <minchan@kernel.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>,
	Inki Dae <inki.dae@samsung.com>, 'InKi Dae' <daeinki@gmail.com>,
	'Jerome Glisse' <j.glisse@gmail.com>,
	airlied@linux.ie, dri-devel@lists.freedesktop.org,
	kyungmin.park@samsung.com, sw0312.kim@samsung.com,
	linux-mm@kvack.org
Subject: Re: [PATCH 2/2 v3] drm/exynos: added userptr feature.
Date: Thu, 10 May 2012 22:51:38 -0400	[thread overview]
Message-ID: <4FAC7EBA.1080708@gmail.com> (raw)
In-Reply-To: <4FAC623E.7090209@kernel.org>

(5/10/12 8:50 PM), Minchan Kim wrote:
> Hi KOSAKI,
>
> On 05/11/2012 02:53 AM, KOSAKI Motohiro wrote:
>
>>>>> let's assume that one application want to allocate user space memory
>>>>> region using malloc() and then write something on the region. as you
>>>>> may know, user space buffer doen't have real physical pages once
>>>>> malloc() call so if user tries to access the region then page fault
>>>>> handler would be triggered
>>>>
>>>>
>>>> Understood.
>>>>
>>>>> and then in turn next process like swap in to fill physical frame
>>>>> number
>>>> into entry of the page faulted.
>>>>
>>>>
>>>> Sorry, I can't understand your point due to my poor English.
>>>> Could you rewrite it easiliy? :)
>>>>
>>>
>>> Simply saying, handle_mm_fault would be called to update pte after
>>> finding
>>> vma and checking access right. and as you know, there are many cases to
>>> process page fault such as COW or demand paging.
>>
>> Hmm. If I understand correctly, you guys misunderstand mlock. it doesn't
>> page pinning
>> nor prevent pfn change. It only guarantee to don't make swap out. e.g.
>
>
> Symantic point of view, you're right but the implementation makes sure page pinning.
>
>> memory campaction
>> feature may automatically change page physical address.
>
>
> I tried it last year but decided drop by realtime issue.
> https://lkml.org/lkml/2011/8/29/295
>
> so I think mlock is a kind of page pinning. If elsewhere I don't realized is doing, that place should be fixed.
> Or my above patch should go ahead.

Thanks pointing out. I didn't realized your patch didn't merged. I think it should go ahead. think autonuma case,
if mlock disable autonuma migration, that's bug.  I don't think we can promise mlock don't change physical page.
I wonder if any realtime guys page migration is free lunch. they should disable both auto migration and compaction.

And, think if application explictly use migrate_pages(2) or admins uses cpusets. driver code can't assume such scenario
doesn't occur, yes?


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  reply	other threads:[~2012-05-11  2:51 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1335188594-17454-4-git-send-email-inki.dae@samsung.com>
     [not found] ` <1336544259-17222-1-git-send-email-inki.dae@samsung.com>
     [not found]   ` <1336544259-17222-3-git-send-email-inki.dae@samsung.com>
2012-05-09 14:45     ` [PATCH 2/2 v3] drm/exynos: added userptr feature Jerome Glisse
2012-05-09 18:32       ` Jerome Glisse
2012-05-10  2:44         ` Inki Dae
2012-05-10 15:05           ` Jerome Glisse
2012-05-10 15:31             ` Daniel Vetter
2012-05-10 15:52               ` Jerome Glisse
2012-05-11  1:47                 ` Inki Dae
2012-05-11  2:08                   ` Minchan Kim
2012-05-10  1:39       ` Inki Dae
2012-05-10  4:58         ` Minchan Kim
2012-05-10  6:53           ` KOSAKI Motohiro
2012-05-10  7:27             ` Minchan Kim
2012-05-10  7:31               ` Kyungmin Park
2012-05-10  7:56                 ` Minchan Kim
2012-05-10  7:58                   ` Minchan Kim
2012-05-10  6:57           ` Inki Dae
2012-05-10  7:05             ` Minchan Kim
2012-05-10  7:59               ` InKi Dae
2012-05-10  8:11                 ` Minchan Kim
2012-05-10  8:44                   ` Inki Dae
2012-05-10 17:53                     ` KOSAKI Motohiro
2012-05-11  0:50                       ` Minchan Kim
2012-05-11  2:51                         ` KOSAKI Motohiro [this message]
2012-05-11  3:01                           ` Jerome Glisse
2012-05-11 21:20                             ` KOSAKI Motohiro
2012-05-11 22:22                               ` Jerome Glisse
2012-05-11 22:59                                 ` KOSAKI Motohiro
2012-05-11 23:29                                   ` Jerome Glisse
2012-05-11 23:39                                     ` KOSAKI Motohiro
2012-05-12  4:48                                       ` InKi Dae
2012-05-14  4:29                                         ` Minchan Kim
     [not found]   ` <1336976268-14328-1-git-send-email-inki.dae@samsung.com>
2012-05-14  8:12     ` [PATCH 0/2 v4] " Inki Dae
     [not found]     ` <1336976268-14328-2-git-send-email-inki.dae@samsung.com>
2012-05-14  8:12       ` [PATCH 1/2 v4] drm/exynos: added userptr limit ioctl Inki Dae
     [not found]     ` <1336976268-14328-3-git-send-email-inki.dae@samsung.com>
     [not found]       ` <CAHGf_=qv45_uuO_JWMXOQp4VymyOxVq76rGXghoNMmDh7mURKQ@mail.gmail.com>
     [not found]         ` <003001cd319e$263c9230$72b5b690$%dae@samsung.com>
     [not found]           ` <4FB0AE87.60800@gmail.com>
2012-05-14  8:13             ` [PATCH 2/2 v4] drm/exynos: added userptr feature Inki Dae
     [not found]       ` <CAH3drwb13T2RXgEuauGchoZUDAgL+wrv3SR66sZNyGk_6tRTFw@mail.gmail.com>
2012-05-15  4:33         ` Inki Dae
2012-05-15 14:31           ` Jerome Glisse
2012-05-16  8:49             ` Inki Dae

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