Cycles does nothing when the render starts. (In specific scene) #70972

New Issue

Hyesung · 2019-10-20T19:01:30+02:00

Hyesung commented

2019-10-20 19:01:30 +02:00

System Information
Operating system: Windows 10 (1903)
Graphics card: MSI GeForce RTX 2080 AERO 8G
GPU driver version: GEFORCE GAME READY DRIVER 436.48 2019.10.1
Main memory size: Samsung DDR4 32 GB 2666mhz

Blender Version
Broken: blender-2.82-c2a2cd13be2f-windows64-2019-10-19
Worked: blender-2.79b-f4dc9f9d68b-windows64-2018-03-22

Short description of error
Nothing happens during the first 30 seconds when rendering a specific scene in Cycles.

CPU, CUDA, OptiX all have this problem.
Works well immediately in viewport rendering.

Exact steps for others to reproduce the error

Cycles do nothing for the first 30 seconds. (2.80, 2.81, 2.82 are all the same.)
Video → https://d.pr/v/vWhdvC

Cycles viewport rendering works fine. (2.80, 2.81, 2.82 are all the same.)
Video → https://d.pr/v/ysASDJ

It seems to start immediately in 2.79b.
Video → https://d.pr/v/mCP60J

Cycles does nothing when the render starts.blend

**System Information** Operating system: Windows 10 (1903) Graphics card: MSI GeForce RTX 2080 AERO 8G GPU driver version: GEFORCE GAME READY DRIVER 436.48 2019.10.1 Main memory size: Samsung DDR4 32 GB 2666mhz **Blender Version** Broken: blender-2.82-c2a2cd13be2f-windows64-2019-10-19 Worked: blender-2.79b-f4dc9f9d68b-windows64-2018-03-22 **Short description of error** Nothing happens during the first 30 seconds when rendering a specific scene in Cycles. - CPU, CUDA, OptiX all have this problem. - Works well immediately in viewport rendering. **Exact steps for others to reproduce the error** Cycles do nothing for the first 30 seconds. (2.80, 2.81, 2.82 are all the same.) Video → https://d.pr/v/vWhdvC Cycles viewport rendering works fine. (2.80, 2.81, 2.82 are all the same.) Video → https://d.pr/v/ysASDJ It seems to start immediately in 2.79b. Video → https://d.pr/v/mCP60J [Cycles does nothing when the render starts.blend](https://archive.blender.org/developer/F7858582/Cycles_does_nothing_when_the_render_starts.blend)

Hyesung commented

2019-10-20 19:01:30 +02:00

Added subscriber: @Hyesung

dark999 commented

2019-10-20 19:26:05 +02:00

Added subscriber: @dark999

dark999 commented

2019-10-20 19:26:05 +02:00

You forgot to upload a simplest possible .blend file to reproduce this problem, just as you forgot to fill relevant data as request in bug template

The operating system, main memory size, GPU brand and model, GPU driver version and Blender hash or its build date may be needed by developers to investigate this problem

thank you

You forgot to upload a simplest possible .blend file to reproduce this problem, just as you forgot to fill relevant data as request in bug template ```The operating system, main memory size, GPU brand and model, GPU driver version and Blender hash or its build date may be needed by developers to investigate this problem``` thank you

Hyesung commented

2019-10-21 12:39:08 +02:00

I'm sorry I didn't submit properly,
The .blender file is a paid scene, and I'm looking for permission from the copyright holder.
Please understand.

Thank you.

I'm sorry I didn't submit properly, The .blender file is a paid scene, and I'm looking for permission from the copyright holder. Please understand. Thank you.

Hyesung commented

2019-10-26 15:48:53 +02:00

I uploaded a .blend file with the permission of the copyright holder.

Ray molenkamp commented

2019-10-26 19:02:44 +02:00

Added subscribers: @Sergey, @LazyDodo

Sergey Sharybin was assigned by Ray molenkamp

2019-10-26 19:02:44 +02:00

Ray molenkamp commented

2019-10-26 19:02:44 +02:00

I can see one of the deg threads holding up things for 37.5 seconds, it seems to be spending an awful lot of time in the OSD code

{F7858981, width=100%}

@Sergey mind taking a look here?

I can see one of the deg threads holding up things for 37.5 seconds, it seems to be spending an awful lot of time in the OSD code {[F7858981](https://archive.blender.org/developer/F7858981/image.png), width=100%} @Sergey mind taking a look here?

Sergey Sharybin commented

2019-10-28 10:42:21 +01:00

This is evaluation of patches which takes a bit. There are some threading issues i've found recently, which is same source of slowdown in #70826.

Sergey Sharybin commented

2019-10-28 10:42:37 +01:00

Closed as duplicate of #70826

Sergey Sharybin closed this issue

2019-10-28 10:42:37 +01:00

Ray molenkamp commented

2019-11-13 19:02:48 +01:00

Thread scheduling doesn't seem to be the issue here it seems to be job size, what is happening is:

Blender schedules the eval of all objects in the scene across all deg threads.
OSD is called with the CPUEvaluator which is single threaded
Given the deg threads work in parallel this gives an even workload distribution across all threads without overloading any cores.

as long as all jobs being scheduled are relatively small this will work out nicely. However in this specific file there is one OSD task that takes 'a bit' and ends up causing the other threads to idle for about 24 seconds.

{F8062968, width=100%}

Solution is gonna be tricky, cause you can't just stick in the multi-threaded OSD eval, since you would end up in context switch hell virtually instantly.

@Sergey up to you if you want to re-open this ticket or not.

Thread scheduling doesn't seem to be the issue here it seems to be job size, what is happening is: 1) Blender schedules the eval of all objects in the scene across all deg threads. 2) OSD is called with the CPUEvaluator which is single threaded 3) Given the deg threads work in parallel this gives an even workload distribution across all threads without overloading any cores. as long as all jobs being scheduled are relatively small this will work out nicely. However in this specific file there is one OSD task that takes 'a bit' and ends up causing the other threads to idle for about 24 seconds. {[F8062968](https://archive.blender.org/developer/F8062968/image.png), width=100%} Solution is gonna be tricky, cause you can't just stick in the multi-threaded OSD eval, since you would end up in context switch hell virtually instantly. @Sergey up to you if you want to re-open this ticket or not.

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Cycles does nothing when the render starts. (In specific scene) #70972