Messages in this thread | | | Date | Fri, 2 Apr 2004 01:39:37 +0100 | From | Jamie Lokier <> | Subject | Re: finding out the value of HZ from userspace |
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Peter Williams wrote: > >When we go to a tickless kernel and offer high-resolution timers to > >userspace, then it will be irrelevant. Until then, or if the kernel > >goes tickless but limits the resolution of timers for efficiency, the > >value of HZ is still relevant. > > The resolution will always be limited. That's the nature of digital > systems. Unlimited resolution would require real "real" numbers and > that's not possible. The nearest you get on a digital system is the > floating point APPROXIMATION to real numbers.
Sure, but HZ will still be irrelevant. There won't be a HZ to report.
> IMHO, as I've said several times, USER_HZ should be changed to be equal > to or greater than HZ. In fact, if having USER_HZ greater than HZ would > still make it unusable for your purposes, I'd change that opinion to say > USER_HZ should be equal to HZ (or, in other words, cease to exist).
It's not possible to change USER_HZ. There are too many programs with the number hard-coded into the binary. The best we could do is make the HZ userspace macro non-constant, so it calls sysconf(_SC_CLK_TCK), and wait a few years until practically all programs being used no longer contain a hard-coded constant. Then we could get rid of USER_HZ again.
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