[ovs-discuss] Some issues about datapath and userspace.

[zuo]

  Hi,
Recently I read the code of OpenvSwitch (version 1.9) to learn how packet is processed in datapath and userspace. However, there are some issues that I didn’t understand clearly. Can anybody help me?
(1)    When the first packet of a flow comes to the datapath, the datapath transmit it to the userspace using netlink. Does the datapath buffer the packet? Or it is just buffered in userspace?
(2)    As the comment of facet introduces, facet is exact-match flow in userspace and subfacet is also exact-match flow in datapath, Can anybody take an example for that one facet has more than one subfacet?
(3)    When the packet comes to the userspace, it is transmited to the controller. However, as my comprehension, before the flow_mod message comes from the controller, it will create a facet in userspace and corresponding subfacet action in SF_fast_path of datapath, so what is the action of the SF_fast_path flow entry? Is it to the userspace or directly to the controller?
(4)    It seems that datapath flow entry is 5 seconds time-out, then how soon is the facet time_out? Where can I find the code of time_out?
(5)    I found that every time it could handle 50(max_batch) upcalls every time? When the traffic in production network is huge, isn’t it small?
Thank you in advance.






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Regards
 
左青云（Roring）
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