From: Karsten Blees <karsten.blees@gmail.com>
To: Noel Grandin <noel@peralex.com>, Git List <git@vger.kernel.org>,
msysGit <msysgit@googlegroups.com>
Subject: Re: [RFC/PATCH v4 1/3] add high resolution timer function to debug performance issues
Date: Wed, 21 May 2014 11:14:16 +0200 [thread overview]
Message-ID: <537C6E68.8030104@gmail.com> (raw)
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
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next prev parent reply other threads:[~2014-05-21 9:14 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <537BA806.50600@gmail.com>
2014-05-20 19:11 ` [RFC/PATCH v4 1/3] add high resolution timer function to debug performance issues Karsten Blees
2014-05-21 7:31 ` Noel Grandin
2014-05-21 9:14 ` Karsten Blees [this message]
2014-05-21 22:14 ` Richard Hansen
2014-05-21 22:17 ` Richard Hansen
2014-05-22 1:33 ` Karsten Blees
2014-05-20 19:11 ` [RFC/PATCH v4 2/3] add trace_performance facility " Karsten Blees
2014-05-21 16:58 ` Jeff King
2014-05-21 18:34 ` Karsten Blees
2014-05-21 20:55 ` Jeff King
2014-05-20 19:11 ` [RFC/PATCH v4 3/3] add command performance tracing to debug scripted commands Karsten Blees
2014-05-21 16:55 ` Jeff King
2014-05-21 17:38 ` Junio C Hamano
2014-05-22 0:40 ` Karsten Blees
2014-05-22 9:59 ` Jeff King
2014-05-23 14:43 ` Karsten Blees
2014-05-23 20:21 ` Jeff King
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