Re: [Xenomai-help] Xenomai 2.5.6 with PPC-Kernel 2.4.25

[Philippe Gerum <rpm@xenomai.org>]

On Tue, 2011-06-21 at 15:05 +0200, roderik.wildenburg@domain.hid
wrote:
> > But more importantly, since, the time when we print the result is so
> > imprecise, some variations are normal, so, chances are that the 2%
> > variation is normal.
> >
> 
> Ok. Here is a switchtest with Xenomai 2.4.9 on PPC-Kernel 2.4.25 and indeed fluctuation is again about 2%.
> But the number of context switches is just about 25% of switchtest from Xeno 2.5.6 on a PPC-2.6.34. Did you change the tasks period from 2.4.9 to 2.5.6?
> So, if the gurus say this variation is within the normal bandwidth it is ok for me.

The number of switches is related to the number of tasks running in this
test, nofpu reduces this number. So that is ok. The problem with this
test is that switches/sec values are sampled by a regular linux thread
which nanosleeps, so at least over 2.4, the delay is not accurate. So
the number of switches observed can't be either.

I still have to check over 2.6 + hires if we can still explain this 2%
offset the same way.

> 
> >Spare time has become a luxury over the last months. I'll try to find a
> >time slot next week to have a look at this again.
> 
> Tanks a lot!
>  I don´t dare to say, but I am on vacation for the rest of this and the next week, so I only can do testing as of 4. of July again.
> 

Ok.

> Roderik
> 
> ----------------------------------------------------------------------------
> Xenomai 2.4.9 on PPC-2.4.25:
> RW24:/fat/sbin # switchtest
> == Testing FPU check routines...
> r0: 1 != 2
> r1: 1 != 2
> r2: 1 != 2
> r3: 1 != 2
> r4: 1 != 2
> r5: 1 != 2
> r6: 1 != 2
> r7: 1 != 2
> r8: 1 != 2
> r9: 1 != 2
> r10: 1 != 2
> r11: 1 != 2
> r12: 1 != 2
> r13: 1 != 2
> r14: 1 != 2
> r15: 1 != 2
> r16: 1 != 2
> r17: 1 != 2
> r18: 1 != 2
> r19: 1 != 2
> r20: 1 != 2
> r21: 1 != 2
> r22: 1 != 2
> r23: 1 != 2
> r24: 1 != 2
> r25: 1 != 2
> r26: 1 != 2
> r27: 1 != 2
> r28: 1 != 2
> r29: 1 != 2
> r30: 1 != 2
> r31: 1 != 2
> == FPU check routines: OK.
> == Threads: sleeper_ufps-0 rtk-1 rtk-2 rtk_fp-3 rtk_fp-4 rtk_fp_ufpp-5 rtk_fp_ufpp-6 rtup-7 rtup-8 rtup_ufpp-9 rtup_ufpp-10 rtus-11 rtus-12 rtus_ufps-13 rtus_ufps-14 rtuo-15 rtuo-16 rtuo_ufpp-17 rtuo_ufpp-18 rtuo_ufps-19 rtuo_ufps-20 rtuo_ufpp_ufps-21 rtuo_ufpp_ufps-22
> RTT|  00:00:01
> RTH|ctx switches|-------total
> RTD|        1150|        1150
> RTD|        1150|        2300
> RTD|        1173|        3473
> RTD|        1173|        4646
> RTD|        1150|        5796
> RTD|        1173|        6969
> RTD|        1150|        8119
> RTD|        1173|        9292
> RTD|        1150|       10442
> RTD|        1173|       11615
> RTD|        1173|       12788
> RTD|        1150|       13938
> RTD|        1173|       15111
> RTD|        1173|       16284
> RTD|        1150|       17434
> RTD|        1150|       18584
> RTD|        1150|       19734
> RTD|        1173|       20907
> RTD|        1150|       22057
> RTD|        1150|       23207
> RTD|        1150|       24357
> RTT|  00:00:22
> RTH|ctx switches|-------total
> RTD|        1173|       25530
> RTD|        1173|       26703
> RTD|        1173|       27876
> RTD|        1173|       29049
> RTD|        1150|       30199
> RTD|        1150|       31349
> RTD|        1150|       32499
> RTD|        1173|       33672
> RTD|        1173|       34845
> RTD|        1173|       36018
> RTD|        1150|       37168
> RTD|        1150|       38318
> RTD|        1150|       39468
> RTD|        1173|       40641
> RTD|        1150|       41791
> RTD|        1150|       42941
> RTD|        1173|       44114
> RTD|        1150|       45264
> RTD|        1150|       46414
> RTD|        1150|       47564
> RTD|        1173|       48737
> RTT|  00:00:43
> RW24:/fat/sbin # cat /proc/xenomai/version
> 2.4.9
> RW24:/fat/sbin # cat /proc/xenomai/sched
> CPU  PID    PRI      PERIOD     TIMEOUT    TIMEBASE  STAT       NAME
>   0  0       -1      0          0          master    R          ROOT
>   0  0       99      200000000  45608637   master    D          rt-watchdog
> RW24:/fat/sbin # cat /proc/xenomai/stat
> CPU  PID    MSW        CSW        PF    STAT       %CPU  NAME
>   0  0      0          38989      0     00500080   98.3  ROOT
>   0  0      0          701        0     00000084    0.0  rt-watchdog
>   0  0      0          14730      0     00000000    0.1  IRQ256: [timer]
> RW24:/fat/sbin #
> 
> 
> > -----Ursprüngliche Nachricht-----
> > Von: Gilles Chanteperdrix [mailto:gilles.chanteperdrix@xenomai.org]
> > Gesendet: Dienstag, 21. Juni 2011 13:33
> > An: Wildenburg, Roderik RAEK1 MRA
> > Cc: rpm@xenomai.org; xenomai@xenomai.org
> > Betreff: Re: AW: AW: [Xenomai-help] Xenomai 2.5.6 with PPC-Kernel 2.4.25
> > 
> > On 06/21/2011 01:22 PM, roderik.wildenburg@domain.hid wrote:
> > >> 2% off seems a lot for a transient load, and this would not happen on a
> > >> periodic basis anyway. This needs to be investigated. Could you run
> > >> switchtest in nofpu mode?
> > >
> > > Still fluctuates about 2% (see !!  mark) but now more erratic. The reduced
> > number of context switches is caused by the reduced number of tasks?
> > 
> > switchest works by switching context between several tasks. One of this
> > task does sleep, in order to avoid starving linux, and also prints the
> > numbers approximately every second.
> > 
> > When there are less task, we enter the sleeping task more often, so,
> > yes, there are less context switches.
> > 
> > But more importantly, since, the time when we print the result is so
> > imprecise, some variations are normal, so, chances are that the 2%
> > variation is normal.
> > 
> > --
> >                                                                 Gilles.
> 
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-- 
Philippe.