Re: GetTickCount on the mac
Re: GetTickCount on the mac
- Subject: Re: GetTickCount on the mac
- From: Andy Wiese <email@hidden>
- Date: Fri, 30 Jan 2009 16:09:50 -0600
On Jan 30, 2009, at 3:22 PM, Jason Coco wrote:
On Jan 30, 2009, at 16:01 , Andy Wiese wrote:
On Jan 30, 2009, at 9:05 AM, Jason Coco wrote:
On Jan 30, 2009, at 09:27 , Christopher Khaljah Xu wrote:
Hi there!
I'm a rookie on a mac. I've been trying to port some windows
programs that was written in C/C++ onto the mac.
I need to rewrite a timer that measures CPU ticks between the
start and end of an operation. I wonder if there is something in
the mac api similar as GetTickCount or GetTickCount64 ?
You can use mach_absolute_time() (declared in mach/mach_time.h)
for this purpose. For more information on using this routine, see
this technical qa: http://developer.apple.com/qa/qa2004/qa1398.html
Jason
How does clock(3) compare to mach_absolute_time()?
mach_absolute_time() actually counts the clock cycles and is the
reference timer for everything else. Internally, from the C library,
clock(3) calls getrusage(2) on itself and returns the converted sum
of its system and user time.
So resolution issues aside (I understand that clock is low
resolution), clock(3) attempts to measure the cpu usage of the
particular process, and mach_absolute_time will give the system global
cpu time. Correct?
So for my purposes, I want rough measurements of a single relatively
long-running task (a cgi handler) in an environment that is polluted
with many such processes, so clock(3) is actually a pretty good
choice. (The fact that the deployment environment is FreeBSD makes it
an even better choice, but that is off-topic and off-platform).
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