I've already finished coding very simple program using vertex shaders,
and I've encounter something weird, namely:
my application draws mesh 1000x1000 quads, I have two ways of doing that
- immediate mode and display list. And it uses vertex program which does
nothing. It is clear that version with DL uses CPU very little and the
immediate mode does it in very intensive way.
Than I put in my vertex empty "for" loop for slowing things down. And
framerate drops just as was supposed, linux's top show me that CPU usage
is very low (<3%) (very good - slower drawing results into slower data
rate) but I can hardly move windows open menus or something.
What is going on? Why top shows no usage at all, and computer looks like
under very heavy load?