[Differential] [Request, 117 lines] D5185: tcp/lro: Allow network drivers to set the limit for TCP ACK/data segment aggregation limit
sepherosa_gmail.com (Sepherosa Ziehau)
phabric-noreply at FreeBSD.org
Thu Feb 4 08:44:10 UTC 2016
sepherosa_gmail.com created this revision.
sepherosa_gmail.com added reviewers: network, adrian, delphij, royger, decui_microsoft.com, honzhan_microsoft.com, howard0su_gmail.com, gallatin, hselasky, np.
sepherosa_gmail.com added subscribers: freebsd-net-list, freebsd-virtualization-list.
Herald added a reviewer: transport.
It's append_cnt based. Unless the network driver sets these two limits, its an NO-OP.
- Set TCP ACK append limit to 1, i.e. aggregate 2 ACKs at most. Aggregate anything more than 2 hurts TCP sending performance in hyperv. This significantly improves the TCP sending performance when the number of concurrent connetion is low (2~8). And greatly stabilize the TCP sending performance in other cases.
- Set TCP data segments append limit to 25. Without this limitation, hn(4) could aggregate ~45 TCP data segments for each connection (even at 64 or more connections) before dispatching them to socket code; large aggregation slows down ACK sending and eventually hurts/destabilizes TCP reception performance. This setting stabilizes and improves TCP reception performance for >4 concurrent connections significantly.
Make them sysctls so they could be adjusted.
To: sepherosa_gmail.com, network, transport, adrian, delphij, royger, decui_microsoft.com, honzhan_microsoft.com, howard0su_gmail.com, gallatin, hselasky, np
Cc: freebsd-virtualization-list, freebsd-net-list
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