Re: Meeting minutes 20060727

[Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>]

Hi Jose,

Jose R. Santos wrote:
> Actually, in the email that was directed at Masami-san I stated two
> scenarios that prevent us just using get_cycles().  One is processors
> that support frequency scaling and the second one is virtulized
> environments like Xen or Power5 micro partitions.  This was something
> that Masami-san and myself were discussing at OLS, as one of his main
> concerns with LKET the performance impact of do_gettimeofday() as a
> timestamp mechanism.  The things that I wrote on my email to Masami-san
> were a continuation of those discussion we had at OLS in an effort to
> standardize the tracing mechanism.

I think we can use get_cycles() even if the processor's frequency can be
changed, because we can re-calculate time by using the events which
records frequency changing. However, in the case of Xen, it would be more
difficult to record these kinds of events.

Thanks,

-- 
Masami HIRAMATSU
2nd Research Dept.
Hitachi, Ltd., Systems Development Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com