From: Jason Ekstrand <jason@jlekstrand.net>
To: Lucas Stach <l.stach@pengutronix.de>
Cc: "Christian König" <ckoenig.leichtzumerken@gmail.com>,
dri-devel <dri-devel@lists.freedesktop.org>,
"Marek Olšák" <maraeo@gmail.com>,
"ML Mesa-dev" <mesa-dev@lists.freedesktop.org>
Subject: Re: [Mesa-dev] [RFC] Linux Graphics Next: Explicit fences everywhere and no BO fences - initial proposal
Date: Tue, 27 Apr 2021 14:41:41 -0500 [thread overview]
Message-ID: <CAOFGe95C78mqV-8-o7PgZ1RZu-OJATVzK4wsS2k9ojXh6ba-tA@mail.gmail.com> (raw)
In-Reply-To: <23ea06c825279c7a9f7678b335c7f89437d387ed.camel@pengutronix.de>
Trying to figure out which e-mail in this mess is the right one to reply to....
On Tue, Apr 27, 2021 at 12:31 PM Lucas Stach <l.stach@pengutronix.de> wrote:
>
> Hi,
>
> Am Dienstag, dem 27.04.2021 um 09:26 -0400 schrieb Marek Olšák:
> > Ok. So that would only make the following use cases broken for now:
> > - amd render -> external gpu
Assuming said external GPU doesn't support memory fences. If we do
amdgpu and i915 at the same time, that covers basically most of the
external GPU use-cases. Of course, we'd want to convert nouveau as
well for the rest.
> > - amd video encode -> network device
>
> FWIW, "only" breaking amd render -> external gpu will make us pretty
> unhappy, as we have some cases where we are combining an AMD APU with a
> FPGA based graphics card. I can't go into the specifics of this use-
> case too much but basically the AMD graphics is rendering content that
> gets composited on top of a live video pipeline running through the
> FPGA.
I think it's worth taking a step back and asking what's being here
before we freak out too much. If we do go this route, it doesn't mean
that your FPGA use-case can't work, it just means it won't work
out-of-the box anymore. You'll have to separate execution and memory
dependencies inside your FPGA driver. That's still not great but it's
not as bad as you maybe made it sound.
> > What about the case when we get a buffer from an external device and
> > we're supposed to make it "busy" when we are using it, and the
> > external device wants to wait until we stop using it? Is it something
> > that can happen, thus turning "external -> amd" into "external <->
> > amd"?
>
> Zero-copy texture sampling from a video input certainly appreciates
> this very much. Trying to pass the render fence through the various
> layers of userspace to be able to tell when the video input can reuse a
> buffer is a great experience in yak shaving. Allowing the video input
> to reuse the buffer as soon as the read dma_fence from the GPU is
> signaled is much more straight forward.
Oh, it's definitely worse than that. Every window system interaction
is bi-directional. The X server has to wait on the client before
compositing from it and the client has to wait on X before re-using
that back-buffer. Of course, we can break that later dependency by
doing a full CPU wait but that's going to mean either more latency or
reserving more back buffers. There's no good clean way to claim that
any of this is one-directional.
--Jason
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next prev parent reply other threads:[~2021-04-27 19:41 UTC|newest]
Thread overview: 105+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-19 10:47 [RFC] Linux Graphics Next: Explicit fences everywhere and no BO fences - initial proposal Marek Olšák
2021-04-19 15:48 ` Jason Ekstrand
2021-04-20 2:25 ` Marek Olšák
2021-04-20 10:15 ` [Mesa-dev] " Christian König
2021-04-20 10:34 ` Daniel Vetter
2021-04-20 11:03 ` Marek Olšák
2021-04-20 11:16 ` Daniel Vetter
2021-04-20 11:59 ` Christian König
2021-04-20 14:09 ` Daniel Vetter
2021-04-20 16:24 ` Jason Ekstrand
2021-04-20 16:19 ` Jason Ekstrand
2021-04-20 12:01 ` Daniel Vetter
2021-04-20 12:19 ` [Mesa-dev] " Christian König
2021-04-20 13:03 ` Daniel Stone
2021-04-20 14:04 ` Daniel Vetter
2021-04-20 12:42 ` Daniel Stone
2021-04-20 15:45 ` Jason Ekstrand
2021-04-20 17:44 ` Daniel Stone
2021-04-20 18:00 ` [Mesa-dev] " Christian König
2021-04-20 18:15 ` Daniel Stone
2021-04-20 19:03 ` Bas Nieuwenhuizen
2021-04-20 19:18 ` Daniel Stone
2021-04-20 18:53 ` Daniel Vetter
2021-04-20 19:14 ` Daniel Stone
2021-04-20 19:29 ` Daniel Vetter
2021-04-20 20:32 ` Daniel Stone
2021-04-26 20:59 ` Marek Olšák
2021-04-27 8:02 ` Daniel Vetter
2021-04-27 11:49 ` Marek Olšák
2021-04-27 12:06 ` Christian König
2021-04-27 12:11 ` Marek Olšák
2021-04-27 12:15 ` Daniel Vetter
2021-04-27 12:27 ` Christian König
2021-04-27 12:46 ` Marek Olšák
2021-04-27 12:50 ` Christian König
2021-04-27 13:26 ` Marek Olšák
2021-04-27 15:13 ` Christian König
2021-04-27 17:31 ` Lucas Stach
2021-04-27 17:35 ` Simon Ser
2021-04-27 18:01 ` Alex Deucher
2021-04-27 18:27 ` Simon Ser
2021-04-28 10:01 ` Daniel Vetter
2021-04-28 10:05 ` Daniel Vetter
2021-04-28 10:31 ` Christian König
2021-04-28 12:21 ` Daniel Vetter
2021-04-28 12:26 ` Daniel Vetter
2021-04-28 13:11 ` Christian König
2021-04-28 13:34 ` Daniel Vetter
2021-04-28 13:37 ` Christian König
2021-04-28 14:34 ` Daniel Vetter
2021-04-28 14:45 ` Christian König
2021-04-29 11:07 ` Daniel Vetter
2021-04-28 20:39 ` Alex Deucher
2021-04-29 11:12 ` Daniel Vetter
2021-04-30 8:58 ` Daniel Vetter
2021-04-30 9:07 ` Christian König
2021-04-30 9:35 ` Daniel Vetter
2021-04-30 10:17 ` Daniel Stone
2021-04-28 12:45 ` Simon Ser
2021-04-28 13:03 ` Alex Deucher
2021-04-27 19:41 ` Jason Ekstrand [this message]
2021-04-27 21:58 ` Marek Olšák
2021-04-28 4:01 ` Jason Ekstrand
2021-04-28 5:19 ` Marek Olšák
2021-04-27 18:38 ` Dave Airlie
2021-04-27 19:23 ` Marek Olšák
2021-04-28 6:59 ` Christian König
2021-04-28 9:07 ` Michel Dänzer
2021-04-28 9:57 ` Daniel Vetter
2021-05-01 22:27 ` Marek Olšák
2021-05-03 14:42 ` Alex Deucher
2021-05-03 14:59 ` Jason Ekstrand
2021-05-03 15:03 ` Christian König
2021-05-03 15:15 ` Jason Ekstrand
2021-05-03 15:16 ` Bas Nieuwenhuizen
2021-05-03 15:23 ` Jason Ekstrand
2021-05-03 20:36 ` Marek Olšák
2021-05-04 3:11 ` Marek Olšák
2021-05-04 7:01 ` Christian König
2021-05-04 7:32 ` Daniel Vetter
2021-05-04 8:09 ` Christian König
2021-05-04 8:27 ` Daniel Vetter
2021-05-04 9:14 ` Christian König
2021-05-04 9:47 ` Daniel Vetter
2021-05-04 10:53 ` Christian König
2021-05-04 11:13 ` Daniel Vetter
2021-05-04 12:48 ` Christian König
2021-05-04 16:44 ` Daniel Vetter
2021-05-04 17:16 ` Marek Olšák
2021-05-04 21:06 ` Jason Ekstrand
2021-04-28 9:54 ` Daniel Vetter
2021-04-27 20:49 ` Jason Ekstrand
2021-04-27 12:12 ` Daniel Vetter
2021-04-20 19:16 ` Jason Ekstrand
2021-04-20 19:27 ` Daniel Vetter
2021-04-20 14:53 ` Daniel Stone
2021-04-20 14:58 ` [Mesa-dev] " Christian König
2021-04-20 15:07 ` Daniel Stone
2021-04-20 15:16 ` Christian König
2021-04-20 15:49 ` Daniel Stone
2021-04-20 16:25 ` Marek Olšák
2021-04-20 16:42 ` Jacob Lifshay
2021-04-20 18:03 ` Daniel Stone
2021-04-20 18:39 ` Daniel Vetter
2021-04-20 19:20 ` Marek Olšák
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