Hi, don't see an improvement with tcp_window_scaling=0 with my configuration. More the other way: the iperf-performance are much less: root at ceph-03:~# iperf -c 172.20.2.14 ------------------------------------------------------------ Client connecting to 172.20.2.14, TCP port 5001 TCP window size: 96.1 KByte (default) ------------------------------------------------------------ [ 3] local 172.20.2.13 port 50429 connected with 172.20.2.14 port 5001 [ ID] Interval Transfer Bandwidth [ 3] 0.0-10.0 sec 2.94 GBytes 2.52 Gbits/sec root at ceph-03:~# sysctl -w "net.ipv4.tcp_window_scaling=1" net.ipv4.tcp_window_scaling = 1 root at ceph-03:~# iperf -c 172.20.2.14 ------------------------------------------------------------ Client connecting to 172.20.2.14, TCP port 5001 TCP window size: 192 KByte (default) ------------------------------------------------------------ [ 3] local 172.20.2.13 port 50431 connected with 172.20.2.14 port 5001 [ ID] Interval Transfer Bandwidth [ 3] 0.0-10.0 sec 11.4 GBytes 9.77 Gbits/sec My kernels are 3.11, 3.14 and the VM-host has an patched rhel-kernel 2.6.32 - the iperf-behavior is between all kernels the same. switched back to net.ipv4.tcp_window_scaling=1 Udo On 24.07.2014 22:15, Jean-Tiare LE BIGOT wrote: > What is your kernel version ? On kernel >= 3.11 sysctl -w > "net.ipv4.tcp_window_scaling=0" seems to improve the situation a lot. > It also helped a lot to mitigate processes going (and sticking) in 'D' > state. > >
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