[Date Prev][Date Next]
[Chronological]
[Thread]
[Top]
Re: [rtl] Stability Problems while generating 1KHz signals
Which kernel patch? I have not seen such bad numbers even on our 486.
I'd like to see more details of the problem. Do you have an old IDE/ISA
controller? What happens when you run sched_toggle?
BTW: This has nothing to do with bottom halves. No linux code can
delay a RTLinux task.
On Tue, Oct 06, 1998 at 03:23:50PM -0500, Manoj Apte wrote:
>
> Hi,
>
> I have been facing a similar problem too. The answer lies somewhere in the
> timer irq that is called every millisecond. I havent been able to nail it
> down yet, but essentially, everytime the timer interrupt is called it
> schedules all the bottom halfs, and due to this the interrupt
> latency for the cpu rises upto the order of about 20us. (thats my take on
> it.. and some people on the linux-kernel newsgroup also pointed to that
> posibility).
>
> manoj
>
>
> On Tue, 6 Oct 1998, Hermann Lauer wrote:
>
> > Dear List reader,
> >
> > I found RTlinux on the net, and tried to generate rectangle signals with it for
> > a stepper motor. I use a periodic scheduled task, very similar to the
> > parallel/sched_toggle.c.
> >
> > But somtimes the stepper motor loses some steps, and an overlay of the signal
> > produced on an oszillosskope shows irregularities in the signal (a shift of one
> > to five periods).
> >
> > We used a rather slow machine (for todays measures), a petium 66.
> >
> > processor : 0
> > cpu : 586
> > model : Pentium 60/66
> > vendor_id : GenuineIntel
> > stepping : 7
> > fdiv_bug : no
> > hlt_bug : no
> > f00f_bug : yes
> > fpu : yes
> > fpu_exception : yes
> > cpuid : yes
> > wp : yes
> > flags : fpu vme de pse tsc msr mce cx8
> > bogomips : 26.52
> >
> > On a faster pentium (166) we see no problems. Has anybody an idea where this
> > delays are comming from ?
> > (delays accessing the LPT port through the pci/isa bus, reloading of
> > primary/secondary level caches...)
> >
> > The rtl_sched uses the timer interrupt, which is also used by linux. Is this a
> > problem or is this known to be save, even if other (non real time) interrupts
> > from other devices (network,scsi) are pending ? Or could there be problems with
> > accessing the Hardware timers (oneshot mode...)?
> >
> > I tried to uses rt_get_time() in the task, to compute the min and max
> > difference between two invocations - the numbers on the 166 MHz are approx: 480
> > min, 520 max.
> >
> > On the 66 MHz they are: ~28 min, up to 6500 max !
> >
> > The used scheduling period is 500.
> >
> > If you are interested in more debugging, please let me know what to do.
> >
> > Thanks for any help/ideas.
> >
> > Greetings
> >
> > Hermann
> >
> > --
> > Hermann Lauer
> >
> > Bildverarbeitungsgruppe des Interdiziplinaeren Zentrums fuer
> > wissenschaftliches Rechnen, Universitaet Heidelberg
> > INF 368; 69120 Heidelberg; Tel: (06221)548826 Fax: (06221)548850
> > Email: Hermann.Lauer@iwr.uni-heidelberg.de
> >
> > --- [rtl] ---
> > To unsubscribe:
> > echo "unsubscribe rtl" | mail majordomo@rtlinux.cs.nmt.edu OR
> > echo "unsubscribe rtl <Your_email>" | mail majordomo@rtlinux.cs.nmt.edu
> > ----
> > For more information on Real-Time Linux see:
> > http://www.rtlinux.org/~rtlinux/
> >
>
> --- [rtl] ---
> To unsubscribe:
> echo "unsubscribe rtl" | mail majordomo@rtlinux.cs.nmt.edu OR
> echo "unsubscribe rtl <Your_email>" | mail majordomo@rtlinux.cs.nmt.edu
> ----
> For more information on Real-Time Linux see:
> http://www.rtlinux.org/~rtlinux/
--
---------------------------------
Victor Yodaiken
Department of Computer Science
New Mexico Institute of Mining and Technology
Socorro NM 87801
Homepage http://www.cs.nmt.edu/~yodaiken
PowerPC Linux page http://linuxppc.cs.nmt.edu
Real-Time Page http://rtlinux.org
--- [rtl] ---
To unsubscribe:
echo "unsubscribe rtl" | mail majordomo@rtlinux.cs.nmt.edu OR
echo "unsubscribe rtl <Your_email>" | mail majordomo@rtlinux.cs.nmt.edu
----
For more information on Real-Time Linux see:
http://www.rtlinux.org/~rtlinux/