Re: 7.52 second kernel compile

[Paul Mackerras <paulus@samba.org>]

Linus Torvalds writes:

> Oh, you're cycle timer is too slow to be interesting, apparently ;(

The G4 has 4 performance monitor counters that you can set up to
measure things like ITLB misses, DTLB misses, cycles spent doing
tablewalks for ITLB misses and DTLB misses, etc.  I hacked up a
measurement of the misses and total cycles doing tablewalks during a
kernel compile and got an average of 36 cycles per DTLB miss and 40
cycles per ITLB miss on a 500MHz G4 machine.  What I need to do now is
to put some better infrastructure for using those counters in place
and try your program using those counters instead of the timebase.

Paul.