Re: [RFC/PATCH v4 1/3] add high resolution timer function to debug performance issues
Am 21.05.2014 09:31, schrieb Noel Grandin:
Show 7 quoted lines
> On 2014-05-20 21:11, Karsten Blees wrote:
>> * implement Mac OSX version using mach_absolute_time
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> Note that unlike the Windows and Linux APIs, mach_absolute_time does not do correction for frequency-scaling
I don't have a MAC so I can't test any of this, but supposedly mach_timebase_info() returns the frequency of mach_absolute_time(), so you could do similar frequency-scaling as I do for Windows with QueryPerformanceFrequency().
> and cross-CPU synchronization with the TSC.
>
The TSC is synchronized across cores and sockets on modern x86 hardware [1] (at least since Intel Nehalem, i.e. all Core i[357] processors). On older machines, I would expect the OS API to choose a more appropriate time source, e.g. the HPET. I'm not proposing to use asm("rdtsc") or anything like that...[1] https://software.intel.com/en-us/articles/best-timing-function-for-measuring-ipp-api-timing
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Karsten Blees <karsten.blees@gmail.com>