Re: [Xenomai-help] memcpy performance on Xenomai

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

Daniel Schnell wrote:
> > -----Original Message-----
> > From: Gilles Chanteperdrix [mailto:gilles.chanteperdrix@xenomai.org
> > Sent: 15. maí 2007 12:16
> > To: Daniel Schnell
> > Cc: xenomai@xenomai.org
> > Subject: Re: [Xenomai-help] memcpy performance on Xenomai
> >
> >
> > Improving clock_gettime overhead by reading directly the tsc is my very next task. If you want to check if the effect you measure is the result of clock_gettime overhead, you can measure the duration of memcpy with the native api service rt_timer_tsc, and convert the tsc difference with rt_timer_tsc2ns.
> 
> This was not the culprit. Same results.

Does your processor have a tsc ? If yes, do you compile Xenomai with
--enable-x86-tsc ? What happens if you disable the interruptions ?

> 
> Does Xenomai replace the memcpy() call with an own implementation ? (I don't think so.)
> 
> What about trashing of cash lines through context switches ? But then if we run it on Linux alone we should also have trashed cache lines. There should not be any difference.
> Is maybe the presence of a Xenomai POSIX thread cause a lot of ctx switches, even if only a memcpy is executed inside the thread ? Shouldn't Xenomai threads run totally uninterrupted if they have the highest prio ?
> 
> Please could somebody actually run this test on his hardware and see if these differences between Xenomai POSIX skin and Linux native are happening there as well ?

If you want us to test the code, please send it, I mean the one adapted
to the native skin.

-- 
                                                 Gilles Chanteperdrix