Am 18.10.19 um 17:36 schrieb Jan Kiszka:
On 18.10.19 17:13, Johannes Holtz via Xenomai wrote:
Am 18.10.19 um 16:57 schrieb Jan Kiszka:
On 18.10.19 16:47, Johannes Holtz via Xenomai wrote:
Am 18.10.19 um 16:33 schrieb Jan Kiszka:
On 18.10.19 16:10, Johannes Holtz via Xenomai wrote:
Hi ,
I inherited a project where the RTnet stack is loaded manually at boot
time. To be specific. Instead of using the rtnet command line programs
the rtnet.ko kernel object as well as the necessary drivers are loaded
with insmod. The devices are then brought up with rtifconfig and
rtroute.
The network consist of 7 PCs (all with the same boot time mechanism)
with pre-defined IPs. The setup works and initializes in an
asynchronized way (like a typical non-RT network).
I'm investigating some performance problems and I don't know whats is
really going on since no config is used. How is determined which
participant is acting as Master and how the slots are distributed?
What
are the default values?
You only mentioned rtifconfig and rtroute above, no rtcfg or tdmacfg.
Are you sure RTmac is involved?
This is the list of kernel object that are loaded:
rtnet.ko
rtipv4.ko
rtpacket.ko
rtudp.ko
rt_e100e.ko
rt_8139too.ko
rt_r8169.ko
subsequently rtifconfig and rtroute
Nothing else is done. I don't know id that satisfies for rtmac. How can
I check?
Nope, there would be rtmac.ko, tdma.ko, possibly also rtcfg.ko in
addition. And you would see the script calling tdmacfg at least.
So this means I basically run standard Ethernet with no RT benefits?
The TX and RX path remain deterministic. If your application behave well
and do not generate overload on the network that can cause switches or
recipients to drop packets, all can still be fine.
Since this is not synced (not TDMA) it is very well possible that
different nodes interfere and datagrams collide.
What would be considered overload? Since the PCs are connected via
unmanaged switches I can't detect if they have any problems.
So, nothing of RTmac should prevent packets from being sent or add size
restrictions on them.
Maybe you can specify your performance problems in more details?
Jan
Well, In this 7 node network one node is receiving datagrams from all
other 6 containing sensor data. Each datagram has a sequence number to
recognize packet loss. Each node is running a RT SW with 1ms loop. In
certain situations the receiver detects that some (between 1 and 20)
datagrams where lost. In these situations the amount of sent datagrams
is higher than usual.
What else is on the network? Only those nodes, and they only sent RT
datagrams at a well-defined rate?
PC1,PC2 <--->Switch1<--->Switch2<---->PC3-7
That's the whole network. Both are un-managed industry switches.
PC2 is the receiver.
At first I though this might be a throughput issue but even after I
reduced the payload size drastically I still miss datagrams. The sender
has no problems sending and my receive code always reads all available
data from the queue.
/proc/rtnet/stats doesn't show any errors or drops .
I'm working on an example program to test this issue in detail.
OK.
Jan
