From: Minchan Kim <minchan@kernel.org>
To: Inki Dae <inki.dae@samsung.com>
Cc: '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 13:58:00 +0900 [thread overview]
Message-ID: <4FAB4AD8.2010200@kernel.org> (raw)
In-Reply-To: <001501cd2e4d$c7dbc240$579346c0$%dae@samsung.com>
On 05/10/2012 10:39 AM, Inki Dae wrote:
> Hi Jerome,
>
>> -----Original Message-----
>> From: Jerome Glisse [mailto:j.glisse@gmail.com]
>> Sent: Wednesday, May 09, 2012 11:46 PM
>> To: Inki Dae
>> Cc: 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.
>>
>> On Wed, May 9, 2012 at 2:17 AM, Inki Dae <inki.dae@samsung.com> wrote:
>>> this feature is used to import user space region allocated by malloc()
>> or
>>> mmaped into a gem. and to guarantee the pages to user space not to be
>>> swapped out, the VMAs within the user space would be locked and then
>> unlocked
>>> when the pages are released.
>>>
>>> but this lock might result in significant degradation of system
>> performance
>>> because the pages couldn't be swapped out so we limit user-desired
>> userptr
>>> size to pre-defined.
>>>
>>> Signed-off-by: Inki Dae <inki.dae@samsung.com>
>>> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
>>
>>
>> Again i would like feedback from mm people (adding cc). I am not sure
>
> Thank you, I missed adding mm as cc.
>
>> locking the vma is the right anwser as i said in my previous mail,
>> userspace can munlock it in your back, maybe VM_RESERVED is better.
>
> I know that with VM_RESERVED flag, also we can avoid the pages from being
> swapped out. but these pages should be unlocked anytime we want because we
> could allocate all pages on system and lock them, which in turn, it may
> result in significant deterioration of system performance.(maybe other
> processes requesting free memory would be blocked) so I used VM_LOCKED flags
> instead. but I'm not sure this way is best also.
>
>> Anyway even not considering that you don't check at all that process
>> don't go over the limit of locked page see mm/mlock.c RLIMIT_MEMLOCK
>
> Thank you for your advices.
>
>> for how it's done. Also you mlock complete vma but the userptr you get
>> might be inside say 16M vma and you only care about 1M of userptr, if
>> you mark the whole vma as locked than anytime a new page is fault in
>> the vma else where than in the buffer you are interested then it got
>> allocated for ever until the gem buffer is destroy, i am not sure of
>> what happen to the vma on next malloc if it grows or not (i would
>> think it won't grow at it would have different flags than new
>> anonymous memory).
I don't know history in detail because you didn't have sent full patches to linux-mm and
I didn't read the below code, either.
Just read your description and reply of Jerome. Apparently, there is something I missed.
Your goal is to avoid swap out some user pages which is used in kernel at the same time. Right?
Let's use get_user_pages. Is there any issue you can't use it?
It increases page count so reclaimer can't swap out page.
Isn't it enough?
Marking whole VMA into MLCOKED is overkill.
--
Kind regards,
Minchan Kim
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next prev parent reply other threads:[~2012-05-10 4:57 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 [this message]
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
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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