Jan Kiszka wrote:
Nathan Lauener wrote:
Jan Kiszka wrote:
Nathan Lauener wrote:
Jan Kiszka wrote:
Lauener Nathan wrote:
Hi, I am using Xenomai to read data from different sensors in real
time from
user space. So far I am reading position data from a device
attached to
a serial port. The CPU load is at about 1%. I also have a
microcontroller attached via USB to read encoder data. The USB
device is
a USB-to-serial converter. As soon as I open the (USB-)serial port
with
normal systemcalls and read the incoming data my CPU load
skyrockets to
over 90%. I only read about 30 bytes every 100ms.
I ran the application on a much newer computer also to rule out any
buggy hardware. The results stayed the same. Intensively searching the
mailing list and provided documentation have not helped solve the
problem. I'm using Xenomai 2.1.0 with kernel 2.6.15.6. Xenomai is
compiled into
the kernel. I also use the driver xeno_16550A loaded as module. The
USB-to-serial bridge used is a CP2101 from Silabs.
Is there any IRQ conflict between the USB host controller and some
RT-device? Please check /proc/interrupts and /proc/xenomai/irq.
There is no conflict (interrupt 0 (timer) is the only interrupt
mentioned in both listings).
Ok, just to exclude this.
Which process is consuming your CPU time? At system or at user level?
It seems that the system consumes the CPU time. Here are the first few
lines from opreport
CPU: CPU with timer interrupt, speed 0 MHz (estimated)
Profiling through timer interrupt
samples % image name app name
symbol name
1733 31.9742 vmlinux vmlinux
default_idle
1151 21.2362 vmlinux vmlinux
__ipipe_trace
601 11.0886 libqt-mt.so.3.3.3 libqt-mt.so.3.3.3 (no
symbols)
528 9.7417 libc-2.3.2.so libc-2.3.2.so (no
symbols)
305 5.6273 vmlinux vmlinux
__ipipe_unstall_root
184 3.3948 vmlinux vmlinux
__ipipe_dispatch_event
122 2.2509 anon (tgid:4322 range:0x81fb000-0x89b2000)
Xorg (no symbols)
100 1.8450 libstdc++.so.5.0.7 libstdc++.so.5.0.7 (no
symbols)
97 1.7897 vmlinux vmlinux
mcount
It looks like the systems gets stuck on the idle task. I do not know
what __ipipe_trace exactly does.
__ipipe_trace belongs to the ipipe-tracer you seem to have patched into
your system. It's called on EVERY kernel function's entry, so it should
show up on higher ranks. Disable the tracer first to get a more
consistent profile.
Jan
In my current design I acquire and process the data in the same programm
using the Xenomai native skin from user space. This means I link the
Xenomai-native and rtdm libraries with several graphics and mathematical
libraries. Could this lead to conflicts or problems with Xenomai?
Should not, we do the same here (e.g. with opencv). Anyway, reducing
your scenario to the minimum that still performs badly can help to
identify the reason.
I compiled a reduced version of my programm and also recompiled the
kernel with tracing switched off. Running it 'top' outputs 40% us, 60%
sys, 0% id => 100% CPU load.
Strange.
'opreport' ouput looks a follows
CPU: CPU with timer interrupt, speed 0 MHz (estimated)
Profiling through timer interrupt
samples % image name app name
symbol name
2517 37.4944 vmlinux vmlinux
default_idle
Almost 40% idle but still 100% loaded? Did anyone else see top&friends
being confused by the presence of Xenomai? I did not so far.
496 7.3886 libc-2.3.2.so libc-2.3.2.so (no
symbols)
385 5.7351 vmlinux vmlinux
__ipipe_dispatch_event
364 5.4223 vmlinux vmlinux
__ipipe_unstall_root
323 4.8116 vmlinux vmlinux
read_chan
269 4.0072 libstdc++.so.5.0.7 libstdc++.so.5.0.7 (no
symbols)
246 3.6645 vmlinux vmlinux
sysenter_past_esp
155 2.3090 anon (tgid:4245 range:0x81fb000-0x89a4000)
Xorg (no symbols)
115 1.7131 vmlinux vmlinux
fget_light
104 1.5492 vmlinux vmlinux
vfs_read
100 1.4896 libpthread-0.60.so libpthread-0.60.so
__pthread_disable_asynccancel
98 1.4599 vmlinux vmlinux
add_wait_queue
97 1.4450 libpthread-0.60.so libpthread-0.60.so
__read_nocancel
93 1.3854 3Dpos 3Dpos
SerialportReader::run()
93 1.3854 libpthread-0.60.so libpthread-0.60.so
__pthread_enable_asynccancel
91 1.3556 vmlinux vmlinux
__ipipe_test_and_stall_root
87 1.2960 vmlinux vmlinux
tty_ldisc_deref
85 1.2662 vmlinux vmlinux
remove_wait_queue
68 1.0130 vmlinux vmlinux
__wake_up
68 1.0130 vmlinux vmlinux
sys_read
66 0.9832 vmlinux vmlinux
__ipipe_restore_root
65 0.9683 vmlinux vmlinux
tty_read
62 0.9236 vmlinux vmlinux
tty_ldisc_try
55 0.8193 vmlinux vmlinux
rw_verify_area
54 0.8044 vmlinux vmlinux
__ipipe_syscall_root
So, on which system service does your application spin then?
read(ttyUSBx)? What is the error code of the service that returns
probably too often? Maybe some timing assumptions of your usb2serial
driver get violated by the presence of the real-time core.
I let my application run but read the USB-serial port using Gtkterm at
the same time. CPU load was at about 3%. This rules out a driver problem
or conflict between Linux and Xenomai or related. I guess I should have
a close look at my realtime/non realtime interactions.
Unfortunately other hardware related problems with the USB sub system
forced us to not use USB for the time beeing. If I should further
investigate the problem and find anything interesting I will of course
let you know.
Thanke you very much for your generous support and donation of time.
Nathan
Jan
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