Messages in this thread | | | Subject | Re: finding out the value of HZ from userspace | From | Arjan van de Ven <> | Date | Sat, 13 Mar 2004 23:41:25 +0100 |
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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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