Why does using a PinnedTask cause severe lag?

[vkensou]

In my main loop I have five tasks:
RootTask -> UpdateTask -> RenderTask -> ImGuiUpdateTask
SubmitTask

I changed ImGuiUpdateTask to an IPinnedTask and bound it to thread 0, but this caused a significant drop in frame rate. According to the profiler, the taskScheduler seems to be waiting on something, while CPU usage has increased a lot. My CPU is an Intel(R) Core(TM) i7-14700K, running Windows 10.

What should I do?

https://github.com/vkensou/PulseEngine/blob/13b7fd6fd8510600bb02283c9d9fec3a0d025217/src/rgframework/src/framework_singlewindow.cpp#L908

[dougbinks]

I can't easily see what is going on from your code, but I'd guess that either the scheduler is waiting for a long task or it is running a long task on thread 0 when you call D->taskScheduler.WaitforTask(&tasksFinished);.

You may want to use priorities to ensure that only high priority tasks are run on thread 0 using D->taskScheduler.WaitforTask(&tasksFinished, enki::TASK_PRIORITY_HIGH ); and making sure to make long running tasks a lower priority.

I also noticed that you appear to be calling WaitforAllAndShutdown() every frame at the end of oval_runloop. You should only do this when you no longer need the taskscheduler.

[dougbinks]

I would recommend using a profiler which can show you which tasks are running such as the ones in https://github.com/dougbinks/enkiTSExamples or https://github.com/wolfpld/tracy

[vkensou]

It seems to be an issue with the Intel(R) Core(TM) i7-14700K. My other computer, which has an AMD Ryzen 5 5600X 6-Core Processor, works perfectly fine.

For the Intel(R) Core(TM) i7-14700K, std::thread::hardware_concurrency() returns 28. I tested that when numTaskThreadsToCreate is set to 12, it doesn't have much impact, but as the value increases, the problem gradually worsens.

[dougbinks]

I do not think the problem is specific to a given processor, there is likely something sub-optimal with the way you are arranging your tasks.