Hi Tonghao, >On Thu, Jul 27, 2017 at 11:38:00PM -0700, Tonghao Zhang wrote: >> When inserting or updating (e.g. emc_insert) a flow to EMC, we compare >> (e.g the hash and miniflow ) the netdev_flow_key. >> If the key is matched, we will update it. If we didn’t find the >> miniflow in the cache, the new flow will be stored. >> >> But when looking up the flow, we compare the hash and miniflow of key >> and make sure it is alive. If a flow is not alive but the key is >> matched, we still will go to next loop. More important, we can’t find >> the flow in the next loop (the flow is not alive in the previous >> loop). This patch simply compares the miniflows of the packets. >> >> The topo is shown as below. VM01 sends TCP packets to VM02, and OvS >> forwards packtets. >> >> VM01 -- OVS+DPDK VM02 -- VM03 >> >> With this patch, the TCP throughput between VMs is 5.37, 5.45, 5.48, >> 5.59, 5.65, 5.60 Gbs/sec avg: 5.52 Gbs/sec >> >> up to: >> 5.64, 5.65, 5.66, 5.67, 5.62, 5.67 Gbs/sec avg: 5.65 Gbs/sec >> >> (maybe ~2.3% performance improve, but it is hard to tell exactly due >> to variance in the test results). >> >> Signed-off-by: Tonghao Zhang <xiangxia.m....@gmail.com> > >Thank you for the patch. I haven't spotted any reviews for this on the mailing >list. I apologize for that--usually I expect to see a review much more quickly >than this. I hope that someone who understands the dpif-netdev code well >will provide a review soon.
I reviewed and tested this patch and the performance improvement is marginal and varies a lot depending on traffic pattern. In the original implementation, if the hashes match and the entry is alive in EMC then the Miniflows are compared using memcmp() and takes Significant cycles. With the change proposed in this patch, if the hash matches we would do the Miniflow comparison(takes significant cycles depending on key->len) and then go on to check if the entry is alive. In case the entry isn't available(With EMC saturated and packets hitting classifier) we probably would have wasted lot of cycles in this case doing the expensive memcmp(). What do you think? - Bhanuprakash. _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev
