On Wed, Jan 08, 2025 at 06:55:16PM +0000, Tvrtko Ursulin wrote: > > On 08/01/2025 16:57, Danilo Krummrich wrote: > > On Wed, Jan 08, 2025 at 03:13:39PM +0000, Tvrtko Ursulin wrote: > > > > > > On 08/01/2025 08:31, Danilo Krummrich wrote: > > > > On Mon, Dec 30, 2024 at 04:52:45PM +0000, Tvrtko Ursulin wrote: > > > > > From: Tvrtko Ursulin <tvrtko.ursu...@igalia.com> > > > > > > > > "Deadline scheduler and other ideas" > > > > > > > > There's a few patches that could be sent outside the scope of this > > > > series, e.g. > > > > the first one. > > > > > > > > I think it would make sense to do so. > > > > > > For now I'll keep them at the head of this RFC and as they get acked or > > > r-b-ed I can easily send them standalone or re-ordered. Until then having > > > the series separate would make the RFC not standalone. > > > > > > > > <tldr> > > > > > Replacing FIFO with a flavour of deadline driven scheduling and > > > > > removing round- > > > > > robin. Connecting the scheduler with dma-fence deadlines. First draft > > > > > and > > > > > testing by different drivers and feedback would be nice. I was only > > > > > able to test > > > > > it with amdgpu. Other drivers may not even compile. > > > > > > > > What are the results from your tests with amdgpu? Do you have some > > > > measurements? > > > > > > We already covered this in the thread with Philipp to a degree. Tl;dr; the > > > main idea is whether we simplify the code and at least not regress. > > > > > > I don't expect improvements on the amdgpu side with the workloads like > > > games > > > and benchmarks. I did not measure anything significant apart that > > > priorities > > > seem to work with the run queues removed. > > > > I appreaciate the effort, and generally I like the idea, but I also must > > admit > > that this isn't the most convincing motiviation for such an integral change > > (especially the "at least not regress" part). > > It is challenging yes. But for completeness the full context of what you > quoted (if you also read my replies to Philipp) was *if* we can shrink the > code base, add some fairness to FIFO, *and* not regress then those three > added together would IMHO not be bad. We shouldn't be scared to touch it > because only touching it you can truly understand the gotchas which any > amount of kerneldoc will not help with. > > I'd still like to encourage you to send the small cleanups separately, get > > them > > in soon and leave the deadline scheduler as a separate RFC. > > > > Meanwhile, Philipp is working on getting documentation straight and digging > > into > > all the FIXMEs of the scheduler getting to a cleaner baseline. And with your > > cleanups you're already helping with that. > > > > For now, I'd prefer to leave the deadline scheduler stuff for when things > > are a > > bit more settled and / or drivers declare the need. > > I just sent v2: > > About motivation for the documenting efforts: > > 13 files changed, 424 insertions(+), 576 deletions(-) > > Fewer lines to document. ;) > > On a serious note, I ordered the series (mostly*) so you can read it in > order and for patches/ideas you like please say and I can extract and send > separately if you want. I am reluctant to extract things beforehand, before > knowing which ones people will like and so far there is only one with acks. > > *) > Mostly because perhaps "drm/sched: Queue all free credits in one worker > invocation" could be interesting to move before the most. >
I looked into this. When I originally changed the scheduler from a kthread to a worker, I designed it the way your patch implements it: looping in the worker until credits run out or no jobs are available. If I recall correctly, the feedback from Christian (or Luben?) was to rely on the work queue's requeuing mechanism to submit more than one job. From a latency perspective, there might be a small benefit, but it's more likely that if you queue two jobs back-to-back, even when relying on the work queue's rescheduling, the first job will still be running on the hardware, nullifying any potential latency improvement. >From a fairness perspective, multiplexing across multiple work queues one job at a time makes a bit more sense, in my opinion. Matt > > > Where something could show is if someone is aware of a workload where > > > normal > > > prio starves low. Since one part of the idea is that with the "deadline" > > > scheme those should work a little bit more balanced. > > > > > > Also again, feedback (including testing feedback from other drivers) would > > > be great, and ideas of which workloads to test. > > > > Unfortunately, there's not much I can tell from the Nouveau side of things, > > since we're using the firmware scheduler scheme (one entity per scheduler) > > and > > hence the scheduling strategy isn't that relevant. > > Yeah. Hopefully someone with more appropriate hardware gets intrigued to try > it out, or to suggest interesting workloads. > > Until then I happy to keep it alive in the background and as said you can > pick and choose the parts you like. > > Regards, > > Tvrtko > > > > > > > > > Btw I will send a respin in a day or so which will clean up some things > > > and > > > adds some more tiny bits. > > > > > > Regards, > > > > > > Tvrtko > >
