Commit c39c4c6a authored Jun 03, 2015 by Wei Liu Committed by David S. Miller Jun 04, 2015

tcp: double default TSQ output bytes limit



Xen virtual network driver has higher latency than a physical NIC.
Having only 128K as limit for TSQ introduced 30% regression in guest
throughput.

This patch raises the limit to 256K. This reduces the regression to 8%.
This buys us more time to work out a proper solution in the long run.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Cc: David Miller <davem@davemloft.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 12e25e10

net/ipv4/tcp_output.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -50,8 +50,8 @@ int sysctl_tcp_retrans_collapse __read_mostly = 1;
		*/
		int sysctl_tcp_workaround_signed_windows __read_mostly = 0;

		/* Default TSQ limit of two TSO segments */
		int sysctl_tcp_limit_output_bytes __read_mostly = 131072;
		/* Default TSQ limit of four TSO segments */
		int sysctl_tcp_limit_output_bytes __read_mostly = 262144;

		/* This limits the percentage of the congestion window which we
		* will allow a single TSO frame to consume. Building TSO frames