[Nouveau] Proposal for a DRM-compliant GPU command scheduler

[Shinpei KATO]

Hi,

I am the main developer of the TimeGraph GPU command scheduler, which was
presented at XDC 2011 in Chicago a few days ago.
Please let me propose this approach to scheduling GPU-accelerated processes
with DRM.

This GPU scheduler will help to prioritize and isolate multiple
GPU-accelerated processes executing concurrently for protecting important
GPU workload in multi-tasking environments. It is designed and implemented
at the DRM level as a "drm_sched" component. Each architecture-dependent
driver (nouveau, radeon, i915, etc.) is also required to call the scheduling
functions provided by this drm_sched component accordingly. Nothing needs to
be changed in user-space runtimes.
The priorities and resource limits can be specified through
"/proc/driver/drm_sched/#PID/{sched_policy,resv_policy,priority,runtime,peri
od}" and/or "/etc/drm_sched.spec". Other user interfaces could also be
possible.
The impact of prioritization and isolation on protecting important
GPU-accelerated processes from competing GPU workload is quite significant
(e.g., 3-D games can run at a 10x~ faster rate, using our GPU scheduler,
when heavy workload is competing the GPU). Performance interference among
GPU-accelerated processes can also be well-controlled.
We can activate this GPU scheduler only when multiple processes use the GPU.
Hence *nothing* would be harmful for a standalone execution.
I felt that the audience at XDC 2011 was pretty supportive for this idea.

TimeGraph is developed in a collaborative project with Carnegie Mellon
University, University of California Santa Cruz, and University of Tokyo.
The project website is: http://rtml.ece.cmu.edu/projects/timegraph/

The documentation about how it works is:
http://rtml.ece.cmu.edu/projects/timegraph/raw-attachment/wiki/documentation
/drm_sched_rtgpu.pdf
More information is available at:
http://rtml.ece.cmu.edu/projects/timegraph/wiki/documentation

The instruction to install our Nouveau-based prototype driver is:
http://rtml.ece.cmu.edu/projects/timegraph/wiki/install
For convenience of development, the GPU scheduler is provided as an
independent kernel module (https://gitorious.org/rtgpu/timegraph), but it
can also be part of DRM.
You will also need the Nouveau-tree Linux kernel patched for drm_sched
(https://gitorious.org/rtgpu/linux-rtgpu). Please see the instruction above.
There are not so many changes applied to the current kernel code, as you can
quickly reference at:
http://rtml.ece.cmu.edu/projects/timegraph/attachment/wiki/install/linux-rtg
pu.patch

I would appreciate any comments and feedback from you.

Best Regards,
- Shinpei Kato