Re: finding out the value of HZ from userspace

[Peter Williams]

Micha Feigin wrote:
> On Sat, Mar 20, 2004 at 12:28:00PM +0100, Stefan Smietanowski wrote:
>
> > > > > there is one. Nothing uses it
> > > > > (sysconf() provides this info)
> > > >
> > > > Seems to me that it would be fairly trivial to modify those programs 
> > > > (that should use this mechanism but don't) to use it?  So why should 
> > > > they be allowed to dictate kernel behaviour?
> > >
> > >
> > > quality of implementation; for example shell scripts that want to do
> > > echo 500 > /proc/sys/foo/bar/something_in_HZ
> > > ...
> > > or /etc/sysctl.conf or ...
> >
> > Then write a simple program already. How hard is it to write a program
> > that does a sysconf() and returns (as ascii of course) just the
> > value of HZ? Then do some trivial calculation off of that.
> >
> > HZ=$(gethz)
> >
> > If your 500 was 5 seconds, do
> >
> > TIME=$[HZ*5]
> > echo $TIME > /proc/sys/foo/bar/something_in_HZ
>
>
> Will this be USER_HZ or kernel HZ?
> Someone earlier suggested it would be USER_HZ which would make it
> pointless.

It has to be whatever enables user space to correctly interpret values 
sent to user space as "ticks".  That means USER_HZ and it's not useless 
as it enables USER_HZ to be different and/or change without breaking 
programs that use values expressed in "ticks".

> > I mean, come on.
> >
> > Then you include it in the default distro of choice so that
> > everybody can use it and there you are.
> >
> > If someone doesn't have "gethz" then they can download it.
> >
> > // Stefan
>
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Dr Peter Williams, Chief Scientist                peterw@xxxxxxxxxx
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