Llvmpipe and softpipe

I am working on REDHAT and OpenSuse with only software rasterizer available.
After some searches, I’m still confused of selection between llvmpipe and softpipe.
In my test case, llvmpipe performs much better than softpipe in fps, so I intend to use llvmpipe by setting environment variable.
But my concern is that is llvmpipe always provided in mesa3d?
If llvmpipe somehow fails to work, will the rasterizer switch to softpipe instead?

It’s possible to build Mesa without the llvmpipe driver. This isn’t particularly common, as llvmpipe doesn’t have any hardware requirements. If Mesa was built without llvmpipe then GALLIUM_DRIVER=llvmpipe will be ignored and the softpipe driver will be used.

The default is llvmpipe if available, otherwise swr (Intel’s software rasteriser) if available, otherwise softpipe (which is always available). softpipe will be significantly slower for anything using complex shaders.

If you’re writing an application, you shouldn’t be caring about any of this. You should leave it up to the system to select and configure the OpenGL driver.

Thanks a lot. It’s very helpful.