[Xorp-users] kernel msg "mroute: pending queue full, dropping entries."

[Alexis de Lattre]

Hello !

I have xorp running on the 2 firewall-routers of my network. I use xorp 
for PIM-SM and IGMP querier functionnality, in order to route multicast 
traffic accross my subnets.

The firewall-routers are Debian 5.0 machines with Debian's 2.6.26-2-686 
kernels. They are running xorp 1.6 (Debian package 1.6-1~rc2 taken from 
Debian Sid).

The first firewall-router is an IGMP querier for a subnet which has 25 
Mbit/s of multicast and doesn't print any particular kernel message.

The other firewall-router (xorp configuration file enclosed) is an IGMP 
querier for a subnet which has a lot of multicast (about 500-600 
Mbit/s). This router frequently prints these kernel messages :

Dec  9 10:53:51 fireaj kernel: [326454.274784] mroute: pending queue 
full, dropping entries.
Dec  9 10:53:58 fireaj kernel: [326461.330570] __ratelimit: 52 messages 
suppressed
Dec  9 10:53:58 fireaj kernel: [326461.330579] mroute: pending queue 
full, dropping entries.

The interface on which it receives the high multicast traffic is a 
Gigabit interface on PCIe bus. The machine is a Pentium D 2.8 Ghz (2 
cores) with 2 Go of RAM. It is not swapping. There are 3 significant 
xorp process in term of CPU ressources :
- xorp_fea process takes 40% of one core
- xorp_pimsm4 takes 35% of one core
- xorp_rtrmgr takes 20% of one core
The result, when I run "dstat", is that one core is 0-5% idle and the 
other core is 95-100% idle. The load on the machine is about 1.7.

At the moment, these is only very low inter-subnet multicast traffic 
(most of the time 0 Mbit/s, sometimes a few Mbit/s), so not many PIM 
requests.

What does these "pending queue full, dropping entries" kernel messages 
mean ? What should I do to prevent these message from appearing ?

Thanks in advance for your help !

-- 
Alexis de Lattre

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