Hello, > Does the VS build target a more > recent Windows runtime than the legacy one (msvcrt.dll) that mingw > would link against?
Yes, VS build targets Universal CRT, while mingw targets "classis", pre-Visual Studio 2015 CRT. Answering to Gert's question in IRC - CPU load was 25% on 4-core machine, so I assume that client is CPU-bound. I enabled optimization (-O2 -flto) for mingw builds https://github.com/OpenVPN/openvpn-build/pull/153/commits/570bbbb27ec33f06995400b19da5db2af8b0d58a and problem seems to be fixed, I see no big difference with Visual Studio anymore. I performed series of tests - for each configuration I ran > iperf3.exe -c 10.8.0.1 -t 60 -V five times and used average download bandwidth value. Results below (don't know why they're bit lower comparison to previous runs, probably AWS datacenter has a bad day today): Server - openvpn 2.4.4, client tun driver - tap-windows6 mingw, no optimization - 334Mbit/s (that's what we have in windows release now) mingw, optimized - 390Mbit/s VS2019 release - 394Mbit/s Server - openvpn 2.4.4, client tun driver - wintun mingw, no optimization - 650Mbit/s mingw, optimized - 731Mbit/s VS2019 release - 721Mbit/s Server - openvpn3 with kernel module, client tun driver - wintun mingw, no optimization - 772Mbit/s mingw, optimized - 924Mbit/s VS2019 release - 901Mbit/s As you can see, using wintun and mingw optimization increases download bandwidth more than twice (334Mbit/s -> 731Mbit) So for the next release we need to build client with optimization enabled and it would be nice to have wintun support in 2.5 (see https://patchwork.openvpn.net/project/openvpn2/list/?series=545) -- -Lev
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