From: Karsten Blees Date: Wed, 21 May 2014 09:14:16 GMT Subject: Re: [RFC/PATCH v4 1/3] add high resolution timer function to debug performance issues Message-ID: <537C6E68.8030104@gmail.com> In-Reply-To: <537C5634.3050807@peralex.com> Am 21.05.2014 09:31, schrieb Noel Grandin: > On 2014-05-20 21:11, Karsten Blees wrote: >> * implement Mac OSX version using mach_absolute_time >> >> > > > 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 -- -- *** Please reply-to-all at all times *** *** (do not pretend to know who is subscribed and who is not) *** *** Please avoid top-posting. *** The msysGit Wiki is here: https://github.com/msysgit/msysgit/wiki - Github accounts are free. You received this message because you are subscribed to the Google Groups "msysGit" group. To post to this group, send email to msysgit@googlegroups.com To unsubscribe from this group, send email to msysgit+unsubscribe@googlegroups.com For more options, and view previous threads, visit this group at http://groups.google.com/group/msysgit?hl=en_US?hl=en --- You received this message because you are subscribed to the Google Groups "msysGit" group. To unsubscribe from this group and stop receiving emails from it, send an email to msysgit+unsubscribe@googlegroups.com. For more options, visit https://groups.google.com/d/optout.