Messages in this thread | | | Date | Tue, 16 Mar 2004 16:53:25 +1100 | From | Peter Williams <> | Subject | Re: finding out the value of HZ from userspace |
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Andi Kleen wrote: > Peter Williams <peterw@aurema.com> 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@aurema.com 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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