Subject: Re: Proposed changes to cc_microset().
To: Alan Barrett <firstname.lastname@example.org>
From: Frederick Bruckman <email@example.com>
Date: 07/08/2004 09:59:27
On Thu, 8 Jul 2004, Alan Barrett wrote:
> While you are changing things in this area, it would be nice if you also
> added a way for cc_microtime and friends to be informed of deliberate
> changes in CPU speed (such as the i386 "Enhanced SpeedStep" stuff in
> I haven't worked out the details, but I think that it should be possible
> to add a function that gets called with both old and new nominal speeds
> when the CPU speed is changed, and that frobs the information in struct
> cpu_info to DTRT.
There really is no "nominal" speed: ci_tsc_freq is set at boot-up by
averaging over a 10 tick interval, then not touched again. The ES code
could do the same thing, then set ci_cc_denom = 0 to force ci_tsc_freq
to be used until cc_microset() has a chance to do it's thing. At some
point, when the confidence is high, we should probably update
ci_tsc_freq, as it is used as a fallback at times.