Compositor: Scheduling
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Authored by Jeroen Bakker (jbakker) on Apr 6 2021, 4:53 PM.

Details

Reviewers

Manuel Castilla (manzanilla)
Sergey Sharybin (sergey)

Summary

This started out with tweaking the WorkScheduler of the compositor and tying out different scheduling strategies.

Fix work packages that ran multiple time due to race condition.
Keep the relation with parent/child WorkPackages around.
Cleaner scheduling code.
Enables access to write buffers by operators. See D10861: Compositor: Merge SingleThreadedOperation with WriteBufferOperation. with an example.

Scheduling modes:

Input to output: mode where input nodes are calculated and after finished their child nodes.
Output to input: same behavior as master where tiles are prioritized to show something to the user.

These modes can be switched in COM_defines.h COM_SCHEDULING_MODE.

Scheduling Back-ends:

BLI_task
pthread queue

The back-end can be switched in COM_WorkScheduler.cc COM_threading_model.

Test File:

compositor-scheduling.blend956 KBDownload

Timing patch for master:

master-compositor-timing.diff1 KBDownload

Timing patch for temp-compositor-scheduling:

temp-compositor-scheduling-timing.diff1 KBDownload

AMD Ryzen 1700, Linux

branch	scheduling mode	scheduling backend	time ExecutionSystem.execute
master	Output to input	pthread_queue	3.15s
temp-compositor-scheduling	Output to input	pthread_queue	3.09s
temp-compositor-scheduling	Input to output	pthread_queue	3.49s
temp-compositor-scheduling	Output to input	BLI_task	3.35s
temp-compositor-scheduling	Input to output	BLI_task	3.09s

Diff Detail

Repository

rB Blender

Branch

temp-compositor-scheduling

Build Status

Buildable 13904
Build 13904: arc lint + arc unit

Event Timeline

Jeroen Bakker (jbakker) requested review of this revision.Apr 6 2021, 4:53 PM

Jeroen Bakker (jbakker) created this revision.

Harbormaster completed remote builds in B13896: Diff 35907.Apr 6 2021, 4:53 PM

Jeroen Bakker (jbakker) edited the summary of this revision. (Show Details)Apr 6 2021, 5:06 PM

Jeroen Bakker (jbakker) retitled this revision from [WIP] Compositor: Scheduling to Compositor: Scheduling.Apr 6 2021, 5:12 PM

Jeroen Bakker (jbakker) edited the summary of this revision. (Show Details)

Jeroen Bakker (jbakker) added reviewers: Manuel Castilla (manzanilla), Sergey Sharybin (sergey).

Jeroen Bakker (jbakker) added inline comments.Apr 6 2021, 5:41 PM

source/blender/compositor/intern/COM_ExecutionSystem.cc
292	100ms is too long. We should not sleepnet yield other threads

Jeroen Bakker (jbakker) edited the summary of this revision. (Show Details)Apr 7 2021, 10:54 AM

Jeroen Bakker (jbakker) edited the summary of this revision. (Show Details)

Replace sleep with yield.

Harbormaster completed remote builds in B13904: Diff 35924.Apr 7 2021, 11:02 AM

Jeroen Bakker (jbakker) added inline comments.Apr 7 2021, 11:03 AM

source/blender/compositor/intern/COM_ExecutionSystem.cc
293	Replace with `BLI_condition_*`.

Jeroen Bakker (jbakker) added a child revision: D10861: Compositor: Merge SingleThreadedOperation with WriteBufferOperation..Apr 7 2021, 11:05 AM

Jeroen Bakker (jbakker) mentioned this in D10861: Compositor: Merge SingleThreadedOperation with WriteBufferOperation..Apr 7 2021, 11:12 AM

Merge branch 'master' into temp-compositor-scheduling
Compostior: Test for break to stop compositing.
Tweaked InputToOutput scheduling.

Harbormaster completed remote builds in B14029: Diff 36118.Apr 13 2021, 10:49 AM

Looks good to me. I've tested both modes and haven't found any issue. Thanks to this patch it should be easy to know when all readers of an execution group have finished and free its buffer.

This revision is now accepted and ready to land.Apr 13 2021, 9:19 PM

Sergey Sharybin (sergey) requested changes to this revision.Apr 14 2021, 11:01 AM

Sergey Sharybin (sergey) added inline comments.

source/blender/blenlib/BLI_threads.h
198 ↗	(On Diff #36118)	What does this function do? As in, write a comment about this function so that BLI's API stays nice and documented.
source/blender/compositor/intern/COM_ExecutionSystem.cc
302–312	I am not really convinced the busy wait is the best approach here: you are occupying a CPU thread to constantly perform checks whether there is still work being done. On a non-trivial node setup it will be a lot of extra work done for no apparent reason. Depending on which threading model is used in compositor, there are better approaches: If you have worker threads which will exit once there is no work to be done you can join the thread, or the pool, or the task scheduler. If the worker threads are always active you'd better use conditional variable, so that worker threads wake up the waiting thread once they've finished work. I also see usage of `ThreadQueue`, so maybe `BLI_thread_queue_wait_finish` implements what you need already. If the busy wait is the best solution here it must be explained why is it so.