> > 2017-01-25 7:52 GMT-08:00 Loftus, Ciara <[email protected]>: > >> 2017-01-22 11:45 GMT-08:00 Jan Scheurich <[email protected]>: > >> > > >> >> It's not a big deal, since the most important use case we have for > >> >> dpif-netdev is with dpdk, but I'd still like the code to behave > >> >> similarly on different platforms. How about defining a function that > >> >> uses random_uint32 when compiling without DPDK? > >> >> > >> >> For testing it's not that simple, because unit tests can be run with > >> >> or without DPDK. It would need to be configurable at runtime. > >> >> Perhaps making EM_FLOW_INSERT_PROB configurable at runtime > would > >> also > >> >> help people that want to experiment with different values, even > >> >> though, based on the comments, I guess they wouldn't really see > much > >> >> difference. > >> >> > >> >> Again, what do you think about simply using counting the packets and > >> >> inserting only 1 every EM_FLOW_INSERT_PROB? > >> >> > >> >> Thanks, > >> >> > >> >> Daniele > >> > > >> > > >> > As far as I know Ciara did some quick tests with a counter-based > >> > implementation and it performed 5% worse for 1K and 4K flows than > then > >> > current patch. Perhaps we could find the reason for that and fix it, but > >> > I > >> > also feel uncomfortable with deterministic insertion of every Nth flow. > This > >> > could lead to very strange lock-step phenomena with typical artificial > test > >> > work loads, which often generate flows round-robin. I would rather use > a > >> > random function, as you suggest, or count "cycles" differently when > >> > compiling without DPDK. > >> > >> Ok, using another pseudo random function when compiling without DPDK > >> sounds > >> good to me. > >> > > > > Any suggestions for the random function? > > I think we can use random_uint32() from lib/random.h > > > > >> > > >> > I agree to making the parameter EM_FLOW_INSERT_PROB configurable > for > >> unit > >> > test or other purposes. Should it be a new option in the OpenvSwitch > table > >> > in OVSDB or rather a run-time parameter to be changed with ovs- > appctl? > >> > >> I think a new option in Openvswitch other_config would be appropriate. > > > > I like this idea. I've started making these changes. How about something > like the following?.. > > > > + <column name="other_config" key="emc-insert-prob" > > + type='{"type": "integer", "minInteger": 0, "maxInteger": > 4294967295}'> > > + <p> > > + Specifies the probability (1/emc-insert-prob) of a flow being > > + inserted into the Exact Match Cache (EMC). Higher values of > > + emc-insert-prob will result in less insertions, and lower > > + values will result in more insertions. A value of zero will > > + result in no insertions and essentially disable the EMC. > > + </p> > > + <p> > > + Defaults to 100 ie. there is 1/100 chance of EMC insertion. > > Looks good to me, thanks. > > I would also add that this only applies to 'netdev' bridges (userspace) and > that > a value of 1 means that every flow is going to be sent to the EMC.
Thanks Daniele. I've posted a v2. Not sure it's the ideal approach so would appreciate your feedback if you get a chance. On a separate note, I'm wondering would now be a good time to consider allowing the size of the EMC to be configurable ie. allow EM_FLOW_HASH_SHIFT or a similar value to be modifiable. Whatever scheme is followed for modifying insert probability could probably be easily be re-used for EMC sizing too. Just an idea! Thanks, Ciara > > > > > Thanks, > > Ciara > > > >> > >> Thanks, > >> > >> Daniele > >> > >> > > >> > Jan > >> > _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
