I've got some evidence. We use both OpenBSD and Linux on our hardware. Using apps that use the FPU, we see a _significant_ performance difference. The problem appears to be that OpenBSD always save/restores, where Linux doesn't. The difference is _very_ noticable. On the order of 10-20% for FPU-heavy applications. Matt -- Matthew D. Dharm Senior Software Designer Momentum Computer Inc. 1815 Aston Ave. Suite 107 (760) 431-8663 X-115 Carlsbad, CA 92008-7310 Momentum Works For You www.momenco.com > -----Original Message----- > From: linux-mips-bounce@linux-mips.org > [mailto:linux-mips-bounce@linux-mips.org]On Behalf Of > Dominic Sweetman > Sent: Tuesday, September 17, 2002 2:44 PM > To: Jun Sun > Cc: linux-mips@linux-mips.org > Subject: Re: [RFC] FPU context switch > > > > Jun Sun (jsun@mvista.com) writes: > > > 1) always blindly save and restore during context switch > (switch_to()) > > Just a suggestion... > > > Not interesting. Just list it here for completeness. > > Agreed, it's not interesting. > > But it would work, every time; while the current scheme has been a > fertile source of interesting bugs. How much useful optimisation > might have been done with the effort required to fix them? > > Saving all the FPU registers on a 400MHz CPU takes about a > tenth of a > microsecond. Does anyone reading this list have evidence > that this is > ever any kind of problem? > > Dominic Sweetman > MIPS Technologies. > >
