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    SubjectRe: finding out the value of HZ from userspace
    On Sat, 2004-03-13 at 23:10, Micha Feigin wrote:
    > On Sat, Mar 13, 2004 at 06:24:31PM +0100, Arjan van de Ven wrote:
    > > On Thu, 2004-03-11 at 15:17, Micha Feigin wrote:
    > > > Is it possible to find out what the kernel's notion of HZ is from user
    > > > space?
    > > > It seem to change from system to system and between 2.4 (100 on i386)
    > > > to 2.6 (1000 on i386).
    > >
    > > if you can see 1000 from userspace that is a bad kernel bug; can you say
    > > where you find something in units of 1000 ?
    > I can't see it from user space. Its in the kernel headers. The thing is
    > I am working on fixes to laptop mode. The problem is it requires
    > changing bdflush and journaled file systems journal flush times. The
    > problem is that some of these (bdflush, xfs) expect the value in jiffies
    > and not seconds or milliseconds so making the initiation script portable
    > requires knowing the value of HZ.

    the kernel side is supposed to use clock_t_to_jiffies() and co for this
    to present a unified HZ to userspace. The internal kernel HZ should
    *NOT* leak out to usespace. Heck it's quite thinkable that in the future
    there will be no such HZ.

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