Am 17.08.2011 10:38, schrieb "Müller, René":
Hi all,
I have an performance issue with socketcan and an MPC5200B. My setup looks like
this:
- MPC5200B board (TQM5200)
- custom base board with two PCA82C251, one for each can controller
- linux-2.6.27.18-denx, I use the mpc52xx driver
- booted with uboot and kernel from flash
- mount root filesystem via NFS
- can0 with 1Mbit/s
- candump -l can0 to tmpfs
Hi René,
can you check if the frames are dropped on socket-level? I assume, that
the candump is not able to dump the stuff into tmpfs at full speed.
See details at:
http://www.mail-archive.com/[email protected]/msg00170.html
As this functionality is only working on a 2.6.33+, i created a patch
for our MPC5200 based system (which has a 2.6.28.10), that upgrades the
CAN network and drivers to a recent functionality (including dropcount,
isotp, cangw and a recent mpc52xx driver).
I can send the (huge) patches to you, if you're interested.
Regards,
Oliver
Now I play with the busload on can0 (generated by CANalyzer and three
CANcaseXL). This leads to the following results:
- 0% to 71% busload -> no missing frames
- 74% busload -> 5% missing frames
- 77% busload -> 10% missing frames
- 90% busload -> 45% missing frames
The missing frames are measured by comparison of the candump log file against
the CANalyzer log file. The indicated busload is measured by CANalyzer. The
cause seems to be very simple: the cpu load is too high (or the cpu is too
slow). When the busload is under 71%, the cpu load is under 100%. When the
busload goes higher than 71%, the cpu load is 100%. This seems to be the cause
for the missing frames.
Has anyone else ever seen such an performance issue? Does someone use the
MPC5200B in high busload environments? Maybe I configured something wrong in my
linux.
What about lincan? It has an character device approach with very little
overhead. Is there an chance, that this will solve my problem?
Best regards,
René
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