On Tue, Feb 19, 2002 at 10:28:35PM -0500, Greg Lindahl wrote: > > Alpha seems to always save the fpu state (the comments say that gcc > always generates code that uses it in every user process.) > I think the comment might be an execuse. :-) Never heard of gcc generating unnecessary floating point code. > I suspect that the optimization of not saving the fpu state for a > process that doesn't use the fpu is the most critical optimization. > And that you do already. If you do use floating point, I think it is pretty common to have only process that uses fpu and runs for very long. In that case, leaving FPU owned by the process also saves quite a bit. > What you propose, locking the fpu owner to the current cpu, will not > result in a fair solution. Imagine a 2 cpu machine with 2 processes > using integer math and 1 using floating point... how much cpu time > will each process get? In this case, proc that uses fpu gets about 50% of one cpu, i.e., 25% of total load, while the other two integer math proces split the rest 75%, which gives 37.5% each. Not too bad in my opinion. > Imagine all the funky effects. Now add in a > MIPS design in which interrupts are not delivered uniformly to all the > cpus... This is chip-specific, I think. Not related to general MIPS arch. Jun
