From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eliezer Tamir Subject: [PATCH v2] socket.7: add description for SO_BUSY_POLL Date: Wed, 10 Jul 2013 17:18:35 +0300 Message-ID: <20130710141835.15799.61657.stgit@ladj378.jer.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: linux-man@vger.kernel.org, David Miller , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Andrew Morton , Eliezer Tamir To: Micahel Kerrisk Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org Add description for the SO_BUSY_POLL socket option to the socket(7) manpage. v2 fixed typos reported by Rasmus Villemoes Signed-off-by: Eliezer Tamir --- man7/socket.7 | 25 +++++++++++++++++++++++++ 1 files changed, 25 insertions(+), 0 deletions(-) diff --git a/man7/socket.7 b/man7/socket.7 index f2213eb..5edcb09 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 may improve latency of some applications, care must be +taken when using it since this will increase both CPU utilization and power usage. + .SS Signals When writing onto a connection-oriented socket that has been shut down (by the local or the remote end)