[ovs-discuss] Flow table size jump and down

david zhang david.zhang.ibm at gmail.com
Tue Apr 30 08:54:43 UTC 2013


We are using OVS for our VDI solution based Citrix Xenserver to provide
15000 virtual desktop.

Recently, we have built a script to monitor the size of OVS flow table. We
found the number of flow entries in flow table jumps up and down between
1500 and 7000 in one heavily used OVS. So we want to understand more about
the flow table.

I have been told the following:

"ovs-vswitchd determines how long the flow should stay in the kernel flow
table.  By default, it expires a flow after five seconds of inactivity.  It
can be more aggressive if the flow table becomes large."

I'd like to know more details about "It can be more aggressive if the flow
table becomes large (Are 7000 flows considered as large?)."?

In addition, 2 more questions:
(1) Does OVS empty and recreate the kernal flow table at some stage?
(2) Can the default flow expire timeout be changed? Like increase to 5mins

Your help is highly appreciated.
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