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+---
+title: "VPP Startup Settings"
+weight: 6
+---
+
+# VPP Startup Settings
+
+CSIT code manipulates a number of VPP settings in startup.conf for
+optimized performance. List of common settings applied to all tests and
+test dependent settings follows.
+
+## Common Settings
+
+List of VPP startup.conf settings applied to all tests:
+
+1. heap-size <value> - set separately for ip4, ip6, stats, main
+   depending on scale tested.
+2. no-tx-checksum-offload - disables UDP / TCP TX checksum offload in
+   DPDK. Typically needed for use faster vector PMDs (together with
+   no-multi-seg).
+3. buffers-per-numa <value> - sets a number of memory buffers allocated
+   to VPP per CPU socket. VPP default is 16384. Needs to be increased for
+   scenarios with large number of interfaces and worker threads. To
+   accommodate for scale tests, CSIT is setting it to the maximum possible
+   value corresponding to the limit of DPDK memory mappings (currently
+   256). For Xeon Skylake platforms configured with 2MB hugepages and VPP
+   data-size and buffer-size defaults (2048B and 2496B respectively), this
+   results in value of 215040 (256 * 840 = 215040, 840 * 2496B buffers fit
+   in 2MB hugepage).
+
+## Per Test Settings
+
+List of vpp startup.conf settings applied dynamically per test:
+
+1. corelist-workers <list_of_cores> - list of logical cores to run VPP
+   worker data plane threads. Depends on HyperThreading and core per
+   test configuration.
+2. num-rx-queues <value> - depends on a number of VPP threads and NIC
+   interfaces.
+3. no-multi-seg - disables multi-segment buffers in DPDK, improves
+   packet throughput, but disables Jumbo MTU support. Disabled for all
+   tests apart from the ones that require Jumbo 9000B frame support.
+4. UIO driver - depends on topology file definition.
+5. QAT VFs - depends on NRThreads, each thread = 1QAT VFs.