On Thu, Jul 2, 2015 at 11:33 PM, Ingo Molnar <[email protected]> wrote: > > * Andy Lutomirski <[email protected]> wrote: > >> If we move even more of this stuff into C, then this problem goes away. >> "call >> enter_from_user_mode" turns into "enter_from_user_mode()" or similar. > > Yes. I think we should first see how that process works out, and then see what > else can be done. For the initial step I'm willing to trade up to 10 cycles in > exchange for sane and maintainable x86 entry code that we can then speed up > ... > > I presume we are still within that budget? >
I haven't benchmarked very carefully. IIRC syscall timing was unaffected by this series. Exceptions ought to be unaffected unless something very weird is going on with the trace cache or branch predictor. IRQs will slow down by a couple cycles (I'm guessing 5, since it's more or less the same change I benchmarked when I was playing with the next pile of patches). My current plan is to try to send the 32-bit asm changes some time next week (after I find a vm86-using DOS game to test) and then the actual performance-affecting patch after that. --Andy -- 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/
