Friday, April 5, 2013

kevent 2 may have been dropped

If you are using iMX233-OLinuXino-MAXI with Archlinux on it, it is highly likely that you might get the following kernel message when you connect your board to the network:
smsc95xx 1-1.1:1.0: eth0: kevent 2 may have been dropped
Users of Raspberry Pi faced the same issue (it has the same network chip on it as the OLinuXuiono).
Here is how to fix it.

Access the console on OLiniXino's ttyAMA0 serial port using PuTTY from your Windows/Linux PC (instructions here).

Issue the following command and reboot the board:

sh -c "echo vm.min_free_kbytes = 8192 >> /etc/sysctl.conf"
sysctl -p

What this does is limit the system memory used by the network device - and so you won't see those annoying messages anymore.

Taken from the discussion on the forum here: Network and system hanging

2 comments:

Zihao Wang said...

I'm using rPi with Archlinux ARM on it and I get that message occasionally. Having read your article, I think I can just ssh into rPi and edit /etc/sysctl.conf(Is is right?). But when I find vm.min_free_kbytes=8192 is already there uncommented. I'm just curious. My rPi runs just fine.

(Except sometimes my rPi stop responding but I think it's another issue because I see errors related to disk IO)

Anurag Chugh said...

Yes, this error doesn't effect the RPi otherwise because the higher layer protocols like TCP have retransmit mechanisms built in so even if the packet is dropped, it will be retransmitted anyway.

Read the Virtuam Memory (vm) System variables are documented here (including min_free_kbytes) https://www.kernel.org/doc/Documentation/sysctl/vm.txt

Maybe you can increase min_free_byte further to prevent packets from being dropped because of lack of memory. Newer RPi have 512 MB RAM.

Also read: http://blogs.linbit.com/p/28/kernel-min_free_kbytes/

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