Re: finding out the value of HZ from userspace

[Peter Williams <peterw@aurema.com>]

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
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