linux-kernel - Re: [Nouveau] [PATCH 09/17] drm/radeon: use common fence implementation for fences

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Date:	Wed, 23 Jul 2014 11:39:51 +0200
From:	Christian König <christian.koenig@....com>
To:	Maarten Lankhorst <maarten.lankhorst@...onical.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>
CC:	Christian König <deathsimple@...afone.de>,
	"Thomas Hellstrom" <thellstrom@...are.com>,
	nouveau <nouveau@...ts.freedesktop.org>,
	LKML <linux-kernel@...r.kernel.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	Ben Skeggs <bskeggs@...hat.com>,
	"Deucher, Alexander" <alexander.deucher@....com>
Subject: Re: [Nouveau] [PATCH 09/17] drm/radeon: use common fence implementation
 for fences

Am 23.07.2014 11:38, schrieb Maarten Lankhorst:
> op 23-07-14 11:36, Christian König schreef:
>> Am 23.07.2014 11:30, schrieb Daniel Vetter:
>>> On Wed, Jul 23, 2014 at 11:27 AM, Christian König
>>> <christian.koenig@....com> wrote:
>>>> You submit a job to the hardware and then block the job to wait for radeon
>>>> to be finished? Well than this would indeed require a hardware reset, but
>>>> wouldn't that make the whole problem even worse?
>>>>
>>>> I mean currently we block one userspace process to wait for other hardware
>>>> to be finished with a buffer, but what you are describing here blocks the
>>>> whole hardware to wait for other hardware which in the end blocks all
>>>> userspace process accessing the hardware.
>>> There is nothing new here with prime - if one context hangs the gpu it
>>> blocks everyone else on i915.
>>>
>>>> Talking about alternative approaches wouldn't it be simpler to just offload
>>>> the waiting to a different kernel or userspace thread?
>>> Well this is exactly what we'll do once we have the scheduler. But
>>> this is an orthogonal issue imo.
>> Mhm, could have the scheduler first?
>>
>> Cause that sounds like reducing the necessary fence interface to just a fence->wait function.
> You would also lose benefits like having a 'perf timechart' for gpu's.

I can live with that, when it reduces the complexity of the fence interface.

Christian.

>
> ~Maarten
>

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