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

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Message-ID: <53CF828E.5020201@canonical.com>
Date:	Wed, 23 Jul 2014 11:38:22 +0200
From:	Maarten Lankhorst <maarten.lankhorst@...onical.com>
To:	Christian König <christian.koenig@....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

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.

~Maarten

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