tcp: TCP Small Queues

[deliverable/linux.git] / Documentation / networking / ip-sysctl.txt

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 47b6c79e9b05a55823176be78125221613f35252..e20c17a7d34e70dc914a490fe3667c7574e93483 100644 (file)
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -551,6 +551,20 @@ tcp_thin_dupack - BOOLEAN
        Documentation/networking/tcp-thin.txt
        Default: 0
 
+tcp_limit_output_bytes - INTEGER
+       Controls TCP Small Queue limit per tcp socket.
+       TCP bulk sender tends to increase packets in flight until it
+       gets losses notifications. With SNDBUF autotuning, this can
+       result in a large amount of packets queued in qdisc/device
+       on the local machine, hurting latency of other flows, for
+       typical pfifo_fast qdiscs.
+       tcp_limit_output_bytes limits the number of bytes on qdisc
+       or device to reduce artificial RTT/cwnd and reduce bufferbloat.
+       Note: For GSO/TSO enabled flows, we try to have at least two
+       packets in flight. Reducing tcp_limit_output_bytes might also
+       reduce the size of individual GSO packet (64KB being the max)
+       Default: 131072
+
 UDP variables:
 
 udp_mem - vector of 3 INTEGERs: min, pressure, max