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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next prev parent 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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