On Fri, 2012-10-26 at 08:39 -0400, Steven Rostedt wrote: > On Fri, 2012-10-26 at 12:36 +0200, Thomas Gleixner wrote: > > > By all means. nsec precision is a completly academic thought > > exercise. It's really pointless to even think about anything below > > microseconds resolution. > > > > We can still have the user space interface handing in the information > > in nsec resolution, but it's reasonable to scale it down to something > > useful. Just shift the incoming information right by 10, so you're in > > the 1us resolution for all the internal math and all your limitation > > problems are gone. A shift by ten for converting back and forth to > > nsecs is not a real performance issue. > > Just make sure this is well documented in the man pages, and that should > eliminate any "surprises". This is a new interface, we can just make > this part of the ABI. "The units are in nanoseconds, but all > calculations are performed to the nearest microsecond. Take this into > account for error analysis". People should be fine with this.
Actually, a shift by 10 is a division by 1024, which is not truly down to a microsecond. Would just a shift by 9 work as well? This would make the resolution closer to a half of microsecond. Otherwise things will probably get screwy if the user passes in 1000 ns, and gets a zero result. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
