From 2d48d67fa8cd129ea85ea02d91b4a793286866f8 Mon Sep 17 00:00:00 2001 From: Eliezer Tamir Date: Mon, 24 Jun 2013 10:28:03 +0300 Subject: net: poll/select low latency socket support select/poll busy-poll support. Split sysctl value into two separate ones, one for read and one for poll. updated Documentation/sysctl/net.txt Add a new poll flag POLL_LL. When this flag is set, sock_poll will call sk_poll_ll if possible. sock_poll sets this flag in its return value to indicate to select/poll when a socket that can busy poll is found. When poll/select have nothing to report, call the low-level sock_poll again until we are out of time or we find something. Once the system call finds something, it stops setting POLL_LL, so it can return the result to the user ASAP. Signed-off-by: Eliezer Tamir Signed-off-by: David S. Miller --- Documentation/sysctl/net.txt | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) (limited to 'Documentation/sysctl') diff --git a/Documentation/sysctl/net.txt b/Documentation/sysctl/net.txt index 5369879eafe2..e658bbfb641f 100644 --- a/Documentation/sysctl/net.txt +++ b/Documentation/sysctl/net.txt @@ -50,13 +50,27 @@ The maximum number of packets that kernel can handle on a NAPI interrupt, it's a Per-CPU variable. Default: 64 -low_latency_poll +low_latency_read ---------------- -Low latency busy poll timeout. (needs CONFIG_NET_LL_RX_POLL) +Low latency busy poll timeout for socket reads. (needs CONFIG_NET_LL_RX_POLL) Approximate time in us to spin waiting for packets on the device queue. +This sets the default value of the SO_LL socket option. +Can be set or overridden per socket by setting socket option SO_LL. Recommended value is 50. May increase power usage. Default: 0 (off) +low_latency_poll +---------------- +Low latency busy poll timeout for poll and select. (needs CONFIG_NET_LL_RX_POLL) +Approximate time in us to spin waiting for packets on the device queue. +Recommended value depends on the number of sockets you poll on. +For several sockets 50, for several hundreds 100. +For more than that you probably want to use epoll. +Note that only sockets with SO_LL set will be busy polled, so you want to either +selectively set SO_LL on those sockets or set sysctl.net.low_latency_read globally. +May increase power usage. +Default: 0 (off) + rmem_default ------------ -- cgit v1.2.1