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From: Eric Anholt <eric@anholt.net>
To: Daniel Vetter <daniel@ffwll.ch>, Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH 18/18] drm/i915: Introduce mapping of user pages into video memory (userptr) ioctl
Date: Tue, 23 Oct 2012 10:50:10 -0700	[thread overview]
Message-ID: <87vce16pt9.fsf@eliezer.anholt.net> (raw)
In-Reply-To: <CAKMK7uH7i9oTbycDkUd6jcsdJsvkezOpf6CC3FhJfard=L_AyQ@mail.gmail.com>


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Daniel Vetter <daniel@ffwll.ch> writes:

> On Tue, Oct 23, 2012 at 12:21 AM, Jesse Barnes <jbarnes@virtuousgeek.org> wrote:
>> On Fri, 19 Oct 2012 18:03:24 +0100
>> Chris Wilson <chris@chris-wilson.co.uk> wrote:
>>
>>> By exporting the ability to map user address and inserting PTEs
>>> representing their backing pages into the GTT, we can exploit UMA in order
>>> to utilize normal application data as a texture source or even as a
>>> render target (depending upon the capabilities of the chipset). This has
>>> a number of uses, with zero-copy downloads to the GPU and efficient
>>> readback making the intermixed streaming of CPU and GPU operations
>>> fairly efficient. This ability has many widespread implications from
>>> faster rendering of client-side software rasterisers (chromium),
>>> mitigation of stalls due to read back (firefox) and to faster pipelining
>>> of texture data (such as pixel buffer objects in GL).
>>>
>>> v2: Compile with CONFIG_MMU_NOTIFIER
>>
>> I want to understand the root-only nature of this better.
>>
>> Is locking complexity the only reason we can't treat these pages like
>> normal BOs which can be swapped out from under us as long as they're
>> not pinned into the GTT?  Or are there other complications in managing
>> the refcount for these pages?
>
> Essentially the complication in pinning tons of memory that we don't
> control, and hence might upset other kernel mm parts (like page
> migration). For native objects we can always fix this by intercepting
> more of the vm callbacks for the shmem backing storage (i.e. gemfs).
> But for foreing storage we need to use the mmu_notifiers, and atm
> those expect that a pte shootdown is synchronous (which we can't do),
> so there's some work left to get done imo.

So, the code isn't done, and the solution is to push it as root-only?
Seriously?

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  reply	other threads:[~2012-10-23 17:50 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-10-19 17:03 [PATCH 01/18] drm: Introduce drm_mm_create_block() Chris Wilson
2012-10-19 17:03 ` [PATCH 02/18] drm/i915: Fix detection of stolen base for gen2 Chris Wilson
2012-11-01 23:51   ` Ben Widawsky
2012-10-19 17:03 ` [PATCH 03/18] drm/i915: Fix location of stolen memory register for SandyBridge+ Chris Wilson
2012-10-26 21:58   ` Ben Widawsky
2012-10-28  9:48     ` Chris Wilson
2012-10-28 17:52       ` Ben Widawsky
2012-11-02  0:08       ` Ben Widawsky
2012-11-02  8:54         ` Chris Wilson
2012-11-05 13:53           ` Ben Widawsky
2012-10-19 17:03 ` [PATCH 04/18] drm/i915: Avoid clearing preallocated regions from the GTT Chris Wilson
2012-10-26 22:22   ` Ben Widawsky
2012-10-19 17:03 ` [PATCH 05/18] drm: Introduce an iterator over holes in the drm_mm range manager Chris Wilson
2012-11-05 13:41   ` Ben Widawsky
2012-11-05 15:13     ` Chris Wilson
2012-10-19 17:03 ` [PATCH 06/18] drm/i915: Delay allocation of stolen space for FBC Chris Wilson
2012-11-05 13:44   ` Ben Widawsky
2012-11-05 15:24     ` Chris Wilson
2012-10-19 17:03 ` [PATCH 07/18] drm/i915: Defer allocation of stolen memory for FBC until actual first use Chris Wilson
2012-11-05 15:00   ` Ben Widawsky
2012-11-05 15:28     ` Chris Wilson
2012-11-05 15:32       ` Ben Widawsky
2012-10-19 17:03 ` [PATCH 08/18] drm/i915: Allow objects to be created with no backing pages, but stolen space Chris Wilson
2012-10-19 17:03 ` [PATCH 09/18] drm/i915: Differentiate between prime and stolen objects Chris Wilson
2012-10-19 17:03 ` [PATCH 10/18] drm/i915: Support readback of stolen objects upon error Chris Wilson
2012-11-05 15:41   ` Ben Widawsky
2012-10-19 17:03 ` [PATCH 11/18] drm/i915: Handle stolen objects in pwrite Chris Wilson
2012-10-19 17:03 ` [PATCH 12/18] drm/i915: Handle stolen objects for pread Chris Wilson
2012-10-19 17:03 ` [PATCH 13/18] drm/i915: Introduce i915_gem_object_create_stolen() Chris Wilson
2012-11-05 16:32   ` Ben Widawsky
2012-11-05 16:59     ` Chris Wilson
2012-11-05 17:34       ` Ben Widawsky
2012-10-19 17:03 ` [PATCH 14/18] drm/i915: Allocate fbcon from stolen memory Chris Wilson
2012-10-19 17:03 ` [PATCH 15/18] drm/i915: Allocate ringbuffers " Chris Wilson
2012-10-19 17:03 ` [PATCH 16/18] drm/i915: Allocate overlay registers " Chris Wilson
2012-11-05 17:39   ` Ben Widawsky
2012-10-19 17:03 ` [PATCH 17/18] drm/i915: Use a slab for object allocation Chris Wilson
2012-10-24 20:21   ` Paulo Zanoni
2012-11-05 17:49   ` Ben Widawsky
2012-11-05 20:57     ` Chris Wilson
2012-11-07 13:59       ` Ben Widawsky
2012-11-05 18:07   ` Ben Widawsky
2012-11-05 18:10     ` Ben Widawsky
2012-10-19 17:03 ` [PATCH 18/18] drm/i915: Introduce mapping of user pages into video memory (userptr) ioctl Chris Wilson
2012-10-22 22:21   ` Jesse Barnes
2012-10-23  7:20     ` Daniel Vetter
2012-10-23 17:50       ` Eric Anholt [this message]
2012-10-26 21:47 ` [PATCH 01/18] drm: Introduce drm_mm_create_block() Ben Widawsky
2012-10-28  9:57   ` Chris Wilson
2012-10-28 18:12     ` Ben Widawsky
2012-10-28 18:14       ` Ben Widawsky

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