Re: finding out the value of HZ from userspace
From: Peter Williams
Date: Tue Mar 16 2004 - 00:58:01 EST
Andi Kleen wrote:
Peter Williams <peterw@xxxxxxxxxx> writes:
This horrible hack of converting all tick values to 100 (from 1000)
for export to user space because a large number of user space programs
assume that HZ is 100 would NOT be necessary if there was a mechanism
whereby user space programs could find out how many ticks there are in
a second instead of having to make assumptions.
Already exists for a long time - AT_CLKTCK. glibc has a nice wrapper
for it too (sysconf)
So it does and POSIX.1 (_SC_CLK_TCK) compliant as well. Unfortunately,
the presence of this functionality makes it VERY difficult to understand
why ticks are being converted from HZ==1000 values to HZ=100 values when
they are being exported to user space especially as this conversion
throws away precision. Can anyone enlighten me?
Peter
--
Dr Peter Williams, Chief Scientist peterw@xxxxxxxxxx
Aurema Pty Limited Tel:+61 2 9698 2322
PO Box 305, Strawberry Hills NSW 2012, Australia Fax:+61 2 9699 9174
79 Myrtle Street, Chippendale NSW 2008, Australia http://www.aurema.com
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