On 22/07/14 14:15, Daniel Vetter wrote:
On Tue, Jul 22, 2014 at 12:52:43PM +0300, Oded Gabbay wrote:
On 22/07/14 12:21, Daniel Vetter wrote:
On Tue, Jul 22, 2014 at 10:19 AM, Oded Gabbay <oded.gabbay@xxxxxxx> wrote:
Exactly, just prevent userspace from submitting more. And if you have
misbehaving userspace that submits too much, reset the gpu and tell it
that you're sorry but won't schedule any more work.
I'm not sure how you intend to know if a userspace misbehaves or not. Can
you elaborate ?
Well that's mostly policy, currently in i915 we only have a check for
hangs, and if userspace hangs a bit too often then we stop it. I guess
you can do that with the queue unmapping you've describe in reply to
Jerome's mail.
-Daniel
What do you mean by hang ? Like the tdr mechanism in Windows (checks if a
gpu job takes more than 2 seconds, I think, and if so, terminates the job).
Essentially yes. But we also have some hw features to kill jobs quicker,
e.g. for media workloads.
-Daniel
Yeah, so this is what I'm talking about when I say that you and Jerome come from
a graphics POV and amdkfd come from a compute POV, no offense intended.
For compute jobs, we simply can't use this logic to terminate jobs. Graphics are
mostly Real-Time while compute jobs can take from a few ms to a few hours!!! And
I'm not talking about an entire application runtime but on a single submission
of jobs by the userspace app. We have tests with jobs that take between 20-30
minutes to complete. In theory, we can even imagine a compute job which takes 1
or 2 days (on larger APUs).
Now, I understand the question of how do we prevent the compute job from
monopolizing the GPU, and internally here we have some ideas that we will
probably share in the next few days, but my point is that I don't think we can
terminate a compute job because it is running for more than x seconds. It is
like you would terminate a CPU process which runs more than x seconds.
I think this is a *very* important discussion (detecting a misbehaved compute
process) and I would like to continue it, but I don't think moving the job
submission from userspace control to kernel control will solve this core problem.
Oded
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