path: root/Documentation/sysctl
diff options
authorEliezer Tamir <eliezer.tamir@linux.intel.com>2013-06-24 10:28:03 +0300
committerDavid S. Miller <davem@davemloft.net>2013-06-25 16:35:52 -0700
commit2d48d67fa8cd129ea85ea02d91b4a793286866f8 (patch)
treebe47e2406605760d949b08d29d988d46c4a20799 /Documentation/sysctl
parente4f2379db6c6823c5d4a4c2c912df00c65de51d7 (diff)
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 <eliezer.tamir@linux.intel.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'Documentation/sysctl')
1 files changed, 16 insertions, 2 deletions
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 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 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)