[LAD] [Jack-Devel] How is the TSC calibration accuracy on dual core 2 computers? (And what about HPET?)

Lee Revell rlrevell at joe-job.com
Thu Apr 30 02:26:01 UTC 2009

On Wed, Apr 29, 2009 at 6:19 AM, Kjetil S. Matheussen
<k.s.matheussen at notam02.no> wrote:
> Hard to say. This is for testing a couple of garbage collectors, and the
> difference between worst case and best case can be quite high.
> Worst-case is probably around 1ms, and best case maybe around 0.1ms.
> It also depends on buffer settings, so I can use higher buffers
> to get higher timings.
> But calls to clock_gettime()/HPET/etc. will only happen maximum 6 times
> per audio block, so clock_gettime()/HPET/etc. doesn't have to be extremely
> efficient.

With a modern kernel clock_gettime() should always be the best choice.
 The kernel's timekeeping system has been completely redone since the
days when JACK needed to use its own timers.  Linux is now very good
at picking the cheapest working clock source.

If there were no need to support old kernels, I think JACK's hardware
timer support could be removed entirely in favor of the POSIX clock


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