RE: timing an application

[David Mosberger <davidm@napali.hpl.hp.com>]

>>>>> On Tue, 14 Jan 2003 12:37:05 -0800, "Howell, David P" <david.p.howell@intel.com> said:

  Dave> If this is on a IA32(Pentium II or later)/IA64 have you
  Dave> considered using the processor TSC register to get interval
  Dave> timestamps? It's a lot lighter weight and should give better
  Dave> resolution. When we have done this we compared the tick values
  Dave> directly.

  Dave> To convert TSC ticks to time the /proc/cpuinfo value for 'cpu
  Dave> MHz', see the glibc get_clockfreq.c and hp_timing.h
  Dave> implementation for details.

Note that it's tricky to uses TSC/ITC on multiprocessors, especially
on large machines, on which the clocks for different CPUs may drift, etc.
It's much better to use the clock_gettime() routine:

  http://www.opengroup.org/onlinepubs/007908799/xsh/clock_getres.html

Where properly implemented, this will be both as fast and accurate.

	--david