Re: [RFC patch 0/4] TSC calibration improvements

[Ingo Molnar]

* Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

> "expect" is an unsigned char. There are absolutely _zero_ issues with 
> overflow, underflow, random phases of the moon, madness levels or 
> anything else. But yes, it does look like Ingo screwed up when adding 
> that final check, since expect was already decremented at the end of 
> the loop.
> 
> Ingo? Did you actually test it?

hm, yes, that's my brown paper bag fault, sorry.

I did that addition in tip/x86/tsc and posted it to you and i did test 
it immediately - and i noticed that i never saw the fast-calibration 
message i expected to see. I even pasted the boot log over irc yesterday 
and i still have it:

 *> [  0.000] TSC: PIT calibration deviates from PMTIMER: 738839 846296.
 *> [  0.000] TSC: Using PIT calibration value
 *> [  0.000] Detected 738.839 MHz processor.
 *> does not seem to trigger anywhere

i wanted to debug that problem straight after i worked down my 800+ 
mails post-vacation mbox :-/ Which state i reached about 2 hours ago so 
i'm now free - the fix is below.

i _think_ that the quality of calibration should now be pretty OK with 
latest -git. The clever fast calibration stuff could be .28 material. 

And/or we could change the 5x 50msec calibration to 3x 30msec right now, 
the precision is still plenty and the 90 msec is then replaced with your 
fast-calibrate method anyway on proper boxes. Hm?

	Ingo

------------------->