[SOLVED] What are llvm_pipe threads?

Issue

I'm writing a Rust app that uses a lot of threads. I noticed the CPU usage was high so I did top and then hit H to see the threads:

    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND                
         
 247759 root      20   0 3491496 104400  64676 R  32.2   1.0   0:02.98 my_app           
 247785 root      20   0 3491496 104400  64676 S  22.9   1.0   0:01.89 llvmpipe-0             
 247786 root      20   0 3491496 104400  64676 S  21.9   1.0   0:01.71 llvmpipe-1             
 247792 root      20   0 3491496 104400  64676 S  20.9   1.0   0:01.83 llvmpipe-7             
 247789 root      20   0 3491496 104400  64676 S  20.3   1.0   0:01.60 llvmpipe-4             
 247790 root      20   0 3491496 104400  64676 S  20.3   1.0   0:01.64 llvmpipe-5             
 247787 root      20   0 3491496 104400  64676 S  19.9   1.0   0:01.70 llvmpipe-2             
 247788 root      20   0 3491496 104400  64676 S  19.9   1.0   0:01.61 llvmpipe-3    

What are these llvmpipe-n threads? Why my_app launches them? Are them even from my_app for sure?

Solution

As HHK links to, the llvmpipe threads are from your OpenGL driver, which is Mesa.

You said you are running this in a VM. VMs usually don't virtualize GPU hardware, so the Mesa OpenGL driver is doing sofware rendering. To achieve better performance, Mesa spawns threads to do parallel computations on the CPU.

Answered By - Colonel Thirty Two