On Saturday 20 June 2009 00:09:56 Jonas Gorski wrote: > > If we do _not_ gain performance, it certainly is not a good idea to waste > > space. > > I would be very surprised if we wouldn't. Every kernel emulated > floating point operation results in an exception and the appropriate > handling (fpu emulation is ugly), while soft-float should stay > completely in user space. > > Also, the mips fpu emulator itself suggests that. > Quoting linux/arch/mips/math-emu/cp1emu.c: > > * Note if you know that you won't have an fpu, then you'll get much > > * better performance by compiling with -msoft-float! > > To get some numbers: Perhaps could somebody test with 'sample' from > libmpcdec the difference in speed between in-kernel emulation and > soft-float? https://dev.openwrt.org/ticket/4715 suggests that the > library depends heavily on floating point when not using fixed point > math.
No you completely got me wrong. I am talking about the performance gain in real life. userspace soft float certainly _is_ faster than kernel float. But _if_ userspace soft float is bigger in size than kernel float, it probably is not worth the space tradeoff, because floating point is hardly used on a router. Did somebody test this: * Image with kernel FP emu disabled and userspace softemu enabled. * Image with kernel FP emu enabled and userspace softemu disabled. Which one is smaller? -- Greetings, Michael. _______________________________________________ openwrt-devel mailing list [email protected] https://lists.openwrt.org/mailman/listinfo/openwrt-devel
