I'm porting a library from Windows to *NIX (currently OSX), does anyone now what function can I use instead of Microsoft's QueryPerformanceCounter and QueryPerformanceFrequency?
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5 Answers
On OSX mach_absolute_time and mach_timebase_info are the best equivalents to Win32 QueryPerformance* functions.
See http://developer.apple.com/library/mac/#qa/qa1398/_index.html
Comments
http://www.tin.org/bin/man.cgi?section=3&topic=clock_gettime (and the other functions mentioned there) - it's Posix! Will fall back to worse counters if HPET is not existent. (shouldn't be a problem though)
http://en.wikipedia.org/wiki/High_Precision_Event_Timer
Resolution should be about +10Mhz.
2 Comments
Left For Archive
clock_gettime is part of the POSIX Realtime Extension, and is unfortunately not implemented on Mac OS X.
Justicle
Not a great answer. clock_gettime isn't supported, and it returns time in seconds, rather than counter ticks (even if it was supported).
Try boost's ptime for portable high-resolution timing.
Update (prompted, 2 years on, by Mark's comment below):
These days I'd use a std::chrono::high_resolution_clock ; example.
2 Comments
Mark Harviston
Looks like that will work on linux/mac, but quoting: Get the UTC time using a sub second resolution clock. On Unix systems this is implemented using GetTimeOfDay. On most Win32 platforms it is implemented using ftime. Win32 systems often do not achieve microsecond resolution via this API. If higher resolution is critical to your application test your platform to see the achieved resolution.
timday
Thanks, ptime not so portable as I thought. Still, you prompted me to update my answer here. See also stackoverflow.com/questions/1487695/…
He asked about OS X. Use these APIs from CoreAudio:
AudioConvertHostTimeToNanos(AudioGetCurrentHostTime()) 
Comments
Back in the day you had either uclock or you delved into assembler to read the RDTSC.
G.
4 Comments
graham.reeds
If you are using a high-resolution timer, the chances are you aren't going to be going into powersaving mode.
ApplePieIsGood
You may not be, but some other process may put the system into that mode. It depends on what kind of constraints your system has. For the general public its not guaranteed.
Ronny Brendel
It will also screw up if your process switches cpus, if I remember correctly ... we have done some evaluation using tsc + linux and the effect of powersaving features. Each core has its own tsc.
Marius
Recent AMD and Intel chips implement consistent RDTSC. Good enough for me.