vrouter-dpdk performance optimization blueprint

Partial-bug: #1767047

Change-Id: I201ec2000e9fd62a90246e18eab4999b90bd1aeb
Signed-off-by: Yi Yang <yi.y.yang@intel.com>

5.1/vrouter-dpdk-performance-optimization.md

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+#1. Introduction
+Optimize contrail-vrouter-dpdk performance by batch processing and caching
+
+#2. Problem statement
+We use vtune and perf to find some hotspots, vr_htable_find_hentry is the biggest hotspot, htable
+implementation is not so efficient, we also find vrouter doesn't use batch processing, these are main
+factors impacting on contrail-vrouter-dpdk performance.
+
+#3. Proposed solution
+We propose to use caching and batch processing to boost performance, we have implemented a prototype for this, performance tuning is ongoing.
+
+#4. Implementation
+##4.1 Use hash table to cache flow table lookup result
+Use a big array to cache flow table lookup results, flow key hash value is used as hash index, flow
+entry pointer is saved in this array to check if there is a hash collision, the old one will be evicted
+if yes, the new one is saved, otherwise the flow is allowed to forward, so remove expensive flow table lookup overhead, we have implemented a prototype for this, performance tuning is ongoing.
+
+##4.3 Do batch processing for vrouter Rx path
+Many projects have proved batch processing is the best way to boost performance because it can make full
+use of cache locality and prefetch, we have implemented a prototype for this, performance tuning is ongoing.
+
+#5. Performance and scaling impact
+##5.1 API and control plane
+No Impact
+
+##5.2 Forwarding performance
+We expect this solution can boost forwarding performance.
+
+#6. Upgrade
+No Impact
+
+#7. Deprecations
+None
+
+#8. Dependencies
+None
+
+#9. Testing
+##9.1 Unit tests
+None
+##9.2 Dev tests
+During Dev phase the developer should test the creation of the new queue for control messages and run
+some basic benchmarks to confirm performance improvement.
+##9.3 System tests
+At system level a full setup with bonding driver should be put in place and verify the stability and 
+performance gain of the system.
+
+#10. Documentation Impact
+None
+
+#11. References
+None
+