On Tue, 18 Mar 2025 12:07:09 +0100 Laurent Vivier <lvivier(a)redhat.com> wrote:____ The results with a 6.14-rc7 + e13b6da7045f:Thanks for checking!From guest: iperf3 -c 10.6.68.254 -P2 -Z -t5 -l 1M -w 16M [SUM] 0.00-5.00 sec 14.8 GBytes 25.4 Gbits/sec 0 sender [SUM] 0.00-5.01 sec 14.8 GBytes 25.4 Gbits/sec receiver From host: iperf3 -c localhost -P2 -Z -t5 -p 10001 -l 1M -w 16M [SUM] 0.00-5.00 sec 28.5 GBytes 48.9 Gbits/sec 0 sender [SUM] 0.00-5.03 sec 28.4 GBytes 48.6 Gbits/sec receiver We have only a 2% improvement.Ouch. :( Then there's something else... by the way, for reference, my investigation back then stopped a bit after: https://archives.passt.top/passt-dev/20241010090801.23da8bff@elisabeth/ that is, I tried zeroing pages "fast": https://archives.passt.top/passt-dev/20241017021027.2ac9ea53@elisabeth/ but it didn't really change the asymmetry. I was getting the same numbers you're getting now. Whatever, I guess it's not so important, just... one day we should figure it out. :) -- Stefano