> > We do have the `used_math' optimisation in there which attempts to avoid > > doing the FP save/restore if the app isn't actually using math. > > No, it's more than that. There's a per-processor "used_math" flag to > determine if we need to _initialize_ the FPU, but on context switches we > always assume the program we're switching to will _not_ use FP, and we > just set the "fault on FP" flag and do not normally restore FP state.
This shows room for optimization; if an app is consistently faulting to use FP after a context switch, in principle the kernel could start to assume that it will in the next timeslice as well. > On the other hand, I also wouldn't be surprised if glibc (or similar I doubt glibc is normally, at least most distros don't ship an SSE enabled glibc, only an "i686" one. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/