2012/2/29 Gilles Chanteperdrix <[email protected]>
> On 02/29/2012 08:44 PM, Charles Lesire-Cabaniols wrote:
> > 2012/2/29 Gilles Chanteperdrix <[email protected]>
> >
> >> On 02/29/2012 07:03 PM, Charles Lesire-Cabaniols wrote:
> >>> 2012/2/29 Gilles Chanteperdrix <[email protected]>
> >>>
> >>>> On 02/29/2012 06:52 PM, Charles Lesire-Cabaniols wrote:
> >>>>> 2012/2/29 Gilles Chanteperdrix <[email protected]>
> >>>>>
> >>>>>> On 02/29/2012 06:29 PM, Charles Lesire-Cabaniols wrote:
> >>>>>>> Hi guys,
> >>>>>>>
> >>>>>>> I have installed a Debian+Xenomai (2.6.0) OS on my Gumstix Overo.
> >>>>>>>
> >>>>>>> I want to evaluate the execution time of a simple program, executed
> >> as
> >>>> a
> >>>>>>> real-time thread.
> >>>>>>>
> >>>>>>> I definitely wonder about which functions to use, as I have
> >> completely
> >>>>>>> inconsistent measures.
> >>>>>>> I have tried using rt_timer_read, rt_timer_tsc, clock_gettime.
> >>>>>>> I also directly read the CNNT register with ARM instructions (which
> >> is
> >>>>>> the
> >>>>>>> only one I think correct) in order to have a (good?) reference.
> >>>>>>> (...)
> >>>>>>> What am I doing wrong?
> >>>>>>
> >>>>>> So, you should printf("%Lu %Lu\n", rt_timer_read(), rt_timer_tsc());
> >>>>>>
> >>>>>> Not printf("%lu", ...)
> >>>>>>
> >>>>>> --
> >>>>>> Gilles.
> >>>>>>
> >>>>>
> >>>>> Effectively, that looks cleaner, thanks:
> >>>>>
> >>>>> ----- Xenomai rt_timer_read -----
> >>>>> start: 49166276042 ; end: 49166432273 ; (s-e): 156231 ; CET: 156231
> >>>>> ----- Xenomai rt_timer_tsc -----
> >>>>> start: 639161547 ; end: 639163539 ; (s-e): 1992 ; CET: 1992
> >>>>> ----- Xenomai clock_gettime -----
> >>>>> [ s] start: 946684855 ; end: 946684855 ; (s-e): 0 ; CET: 0
> >>>>> [ns] start: 275520245 ; end: 275677089 ; (s-e): 156844 ; CET: 156844
> >>>>>
> >>>>> My ARM instruction reads 110554.
> >>>>>
> >>>>> Which Xenomai function should I use?
> >>>>> Which one is supposed to be the more accurate?
> >>>>> Does rt_timer_read return nsecs?
> >>>>> What is the unit of rt_timer_tsc?
> >>>>
> >>>> rt_timer_tsc uses whatever hardware counter is available, you need
> >>>> rt_timer_tsc2ns or rt_timer_ns2tsc to convert between this unit to and
> >>>> from nanoseconds.
> >>>>
> >>>> For more details, see:
> >>>>
> >>>>
> >>>>
> >>
> http://www.xenomai.org/documentation/xenomai-2.6/html/api/group__native__timer.html
> >>>>
> >>>> Depending on how xenomai user-space was compiled, rt_timer_tsc should
> >>>> have the lowest overhead.
> >>>>
> >>>
> >>> And are the default options the best ones?
> >>
> >> Yes, but I am not sure the debian package uses the default one. Please
> >> post here the disassembly of rt_timer_tsc, I will tell you if your
> >> system is compiled for the lowest overhead.
> >>
> >>
> > How to do that?
>
> arm-none-linux-objdump -d /path/to/libnative.so.3 | less
> search <rt_timer_tsc>, when you find it, post the disassembly here.
>
Here it is:
00005a54 <rt_timer_tsc>:
5a54: e59f2034 ldr r2, [pc, #52] ; 5a90
<rt_timer_tsc+0x3c>
5a58: e3e03a0f mvn r3, #61440 ; 0xf000
5a5c: e59f1030 ldr r1, [pc, #48] ; 5a94
<rt_timer_tsc+0x40>
5a60: e08f2002 add r2, pc, r2
5a64: e5133003 ldr r3, [r3, #-3]
5a68: e7921001 ldr r1, [r2, r1]
5a6c: e59f0024 ldr r0, [pc, #36] ; 5a98
<rt_timer_tsc+0x44>
5a70: e2833003 add r3, r3, #3
5a74: e0403283 sub r3, r0, r3, lsl #5
5a78: e92d4010 push {r4, lr}
5a7c: e5910008 ldr r0, [r1, #8]
5a80: e1a0e00f mov lr, pc
5a84: e12fff13 bx r3
5a88: e8bd4010 pop {r4, lr}
5a8c: e12fff1e bx lr
5a90: 000086a4 andeq r8, r0, r4, lsr #13
5a94: 000000ec andeq r0, r0, ip, ror #1
5a98: ffff1004 undefined instruction 0xffff1004
>
> >
> >
> >>> How can I tune the TSC performance?
> >>
> >> You use the --enable-arm-tsc or --disable-arm-tsc option of xenomai
> >> configure script. The default is --enable-arm-tsc=kuser and should be
> >> the best option. If you pass --disable-arm-tsc, rt_timer_tsc will emit a
> >> system call.
> >>
> >>
> > I do not use the debian package, but I compile Xenomai from sources ;
> > actually I have a vanilla kernel and a debain rootfs.
> > I think --enable-arm-tsc is the default then.
>
> Yes.
>
> --
> Gilles.
>
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