[ovs-dev] [netlink v4 31/52] datapath: Change ODP_FLOW_GET to retrieve only a single flow at a time.

[Ben Pfaff]

On Sun, Jan 16, 2011 at 5:36 AM, Jesse Gross <jesse at nicira.com> wrote:
> What do you think the performance impact will be of only querying one
> flow at time?  It shouldn't impact normal forwarding performance but
> for a stats request we could end up having thousands of flows that
> need to be queried individually now.  It's better to start with the
> simple case, so I don't think we should do this now, but it makes me
> wonder.

In short, I don't know.

It depends, first, on how often we actually we were requesting multiple
flows' stats at once.  That only happened, IIRC, in the case of an
OpenFlow with multiple datapath flows.  I don't know how common a case
that is.

Second, Netlink actually allows us to send multiple queries in a single
sendmsg, by concatenating multiple Netlink messages into a single datagram.
So we can actually amortize that half of it if it seems worthwhile.  But
the *responses* will still come as individual messages, so we won't save
anything on that end.

Not sure.