Hi all, Thanks Ben. I have now repeated the -Bsymbolic-functions diagnostic on an NVIDIA BlueField-3 (Arm Cortex-A78AE).
I used a real application workload over the VPP HostStack and a physical 100 GbE link, with four VPP workers. This is not a packet-forwarding benchmark, so the results are expressed in application requests rather than packets. The comparison used the exact same object files; only libvnet was relinked with -Wl,-Bsymbolic-functions. An A/B/A test across six workload profiles showed: - geometric-mean request rate: +4.32% - latency-sensitive profiles: +8% to +11% per core The number of JUMP_SLOT relocations in libvnet decreased from 2,167 to 382. A separate PMU-assisted latency-sensitive run showed +15.35% request rate, with 13.3% fewer cycles per request and 17.6% fewer instructions per request. Unlike Skylake-SP, the raw branch-miss count did not decrease significantly. The microarchitectural signature is therefore different, but the PLT path still has a measurable performance cost on BlueField-3. This supports investigating Ben’s proposal to compile libvnet with hidden visibility and explicit symbol exports. I have not tested that implementation yet; -Bsymbolic-functions remains only a diagnostic here. The next step would be to identify the intended public libvnet API, explicitly export those symbols, and check whether any supported use case relies on interposition. Jerome De : [email protected] <[email protected]> de la part de Benoit Ganne (bganne) via lists.fd.io <[email protected]> Date : jeudi, 23 juillet 2026 à 16:14 À : vpp-dev <[email protected]> Objet : Re: [vpp-dev] Performance impact of internal libvnet PLT calls Hi, > I observed a significant performance impact from internal libvnet calls going > through the PLT on a Xeon Platinum 8168 (Skylake-SP). > As a diagnostic test, I linked libvnet with -Wl,-Bsymbolic-functions. Given that other part of VPP (eg. vppinfra and plugins) are compiled with -fvisibility=hidden with explicit symbol exports, I think we should do the same for libvnet. That should give us the same benefits and would be consistent with the rest of VPP. Thoughts? Best, ben
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