On 4/6/2012 9:20 AM, Jesse Gross wrote:
On Thu, Apr 5, 2012 at 7:16 PM, Masoud Moshref Javadi
<[email protected]> wrote:
I have the following experiment and whenever I check ovs-dpctl dump-flows,
it gives me less than 7k entries:
There are three machines A,B, and C. B runs openvswitch and connect the
other two. A and B send 10k packets each second from different flows to the
other node. I don't use TCP so there is no ack. There should be 20k entries
there after a second but I get at most 7k and the value changes. It seems
that the facet cache cannot hold enough facets, so it replaces them so
often. The high cpu usage for ovs-vswitchd process also confirms this claim
that the cache cannot hold all entries.
As I said before, userspace generally tries to keep the number of
flows installed in the kernel to a few thousand to avoid maintenance
overhead. The contents of the kernel flow cache is an implementation
detail and there's no requirement that it hold everything. If you
want to try different values you can set flow-eviction-threshold in
the config database.
Thank you.
Now suppose that because of this maintenance process and the large
number of active flows we need to go to the userspace so often and this
makes high CPU usage. What will happen to the packets if the machine
cannot handle them with 100% CPU. Is there any DropTail queue there?
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