Linux-kernel mailing list archive 1998-42,: Re: [patch] jiffies wraparound [Re: 2.1.125 Show stopper list: Draft]

# Re: [patch] jiffies wraparound [Re: 2.1.125 Show stopper list: Draft]

Andi Kleen (ak@muc.de)
23 Oct 1998 11:17:55 +0200

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In article <Pine.LNX.3.96.981022230121.23982E-100000@penguin.transmeta.com>,
Linus Torvalds <torvalds@transmeta.com> writes:

> A kernel that exports internal knowledge is a BAD kernel. And I will
> continue to refuse to make bad decisions like a sysctl() interface to HZ.

It already happened: most of the /proc/sys/net/ipv4/route* sysctls are in
jiffies. Also if I understood correctly the idea behind POSIX
sysconf(_CLK_TCK) is to give the application some minimum idea about the
to be expected granuality from timers for realtime purposes. How well this
works in practice I don't know, but I could imagine that it is useful to have
at least a rough idea at runtime of how much of the tv_usec field of struct
timerval is a lie.

if (sysconf(_CLK_TCK) < 500) {
printf("Sorry, you kernel is too slow for me\n");
exit(1);
}

For soft RT apps it makes sense to recompile the kernel with a higher HZ,
and it would be nice if it wasn't required to recompile glibc too @)

-Andi
> -

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