[ClusterLabs] Buffer overflow (re-transmission list)

[satish kumar]

Hello,

I have a four node cluster. Each node connected with a centralized switch.
MTU size is default, 1500. On each node, a program continuously tries to
multi-cast as many messages as possible. With the default settings
(corosync.conf), buffer overflow does *not* occur till program runs on
three nodes. However as soon as fourth node start multi-casting, overflow
occur and significantly reduce the performance.

Why buffer overflow with just four nodes?

Is hardware topology, centralized switch, is not correct?

Later, I reduced window_size and max_messages to 20 and 5 respectively. No
overflow but not sure whether performance is as expected.

I would like to better understand these two parameters. Lets say in a
cluster of four nodes, I have window_size 50 and max_messages also set to
50. Does that mean only one node will be able to multi-cast in a single
token rotation? If one node was not able to multi-cast because window_size
is reached, when and how this node will get opportunity to send message?

Thanks,
Satish
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