Dear Benoit,
there's a lot of local matching and translation between layer2 and layer3 in
your case. I wounder if it is related to the apr cache size and garbage
parameters. I found [http://linux.die.net/man/7/arp]:
gc_interval (since Linux 2.2)
How frequently the garbage collector for neighbor entries should attempt
to run. Defaults to 30 seconds.
gc_stale_time (since Linux 2.2)
Determines how often to check for stale neighbor entries. When a neighbor
entry is considered stale, it is resolved again before sending data to it.
Defaults to 60 seconds.
gc_thresh1 (since Linux 2.2)
The minimum number of entries to keep in the ARP cache. The garbage
collector will not run if there are fewer than this number of entries in the
cache. Defaults to 128.
gc_thresh2 (since Linux 2.2)
The soft maximum number of entries to keep in the ARP cache. The garbage
collector will allow the number of entries to exceed this for 5 seconds before
collection will be performed. Defaults to 512.
gc_thresh3 (since Linux 2.2)
The hard maximum number of entries to keep in the ARP cache. The garbage
collector will always run if there are more than this number of entries in the
cache. Defaults to 1024.
This still seems to be the default on recent kernels, on a box with 3.3.5 I
found
root@bladerunner9 ~ # cat /proc/sys/net/ipv4/neigh/default/gc*
30
60
128
512
1024
If the ARP cache get's exhausted, there must be continous additional ARP
resolution traffic and latency. May you check this theory?
Greetings
Guido
On 2013-04-23 23:34, Benoit Lourdelet wrote:
> Hello,
>
> Forwarding throughput is decreasing gradually as I add containers. I don't
> see any sudden drop.
>
> I we consider aggregated forwarding performance with 100 containers to be
> 1, here are the measurements for
>
> # containers Aggregated throughput
> ------------------------------------
> 100 1
> 500 .71
> 1000 .27
> 1100 .23
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