Add description for the SO_BUSY_POLL socket option to the socket(7) manpage. Signed-off-by: Eliezer Tamir <eliezer.tamir@xxxxxxxxxxxxxxx> --- man7/socket.7 | 25 +++++++++++++++++++++++++ 1 files changed, 25 insertions(+), 0 deletions(-) diff --git a/man7/socket.7 b/man7/socket.7 index f2213eb..27603c9 100644 --- a/man7/socket.7 +++ b/man7/socket.7 @@ -694,6 +694,31 @@ for details on control messages. Gets the socket type as an integer (e.g., .BR SOCK_STREAM ). This socket option is read-only. +.TP +.B SO_BUSY_POLL +Sets the approximate time in microseconds to busy poll on a blocking receive +when there is no data. Increasing this value requires +.BR CAP_NET_ADMIN . +The default for this option is controlled by the +.I /proc/sys/net/core/busy_read +file. + +The value in the +.I /proc/sys/net/core/busy_poll +file determines how long +.BR select (2) +and +.BR poll (2) +will busy poll when they operate on sockets with +.BR SO_BUSY_POLL +set and no events to report are found. + +In both cases busy polling will only be done when the socket last received data +from a network device that supports this option. + +While busy polling my improve latency of some application, care must be +taken when using it since this will increase both CPU utilization power usage. + .SS Signals When writing onto a connection-oriented socket that has been shut down (by the local or the remote end) -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
