Blender appears to be ignoring the thread command line argument (-t). Expected behavior is that when rendering from command line using "-t 1", blender uses a maximimum of 1 thread. This should correspond to roughly 25% CPU usage on a quad-core computer.
Render from command line using:
"blender test.blend -b -t 1 -f 1"
CPU usage of blender process will be 100%; expected is 25% (on quad-core system)
Are you sure you are setting the command line argument correctly? Try running just blender -t 1 and see if while rendering you only see one tile.
Okay, I did some more tests blender test.blend -f 1 -t 1 -b uses 4 threads, but blender test.blend -t 1 -f 1 -b only uses one.
Do you think this is intended behavior? I'd think they should both use only one thread.
Yes see https://docs.blender.org/manual/en/dev/advanced/command_line/arguments.html#argument-order so it has to be set first. We can note this in the docs.
Reverted rBa6b9bd023b18 since this doesn't need to be the first.
The text under Argument Order: covers this already.
Although this is a common problem people run into it could be made more prominent.