netlink-socket: Increase Netlink socket receive buffer size.

Open vSwitch userspace can set up flows at a high rate, but it is somewhat
"bursty" in opportunities to set up flows, by which I mean that OVS sets up
a batch of flows, then goes off and does some other work for a while, then
sets up another batch of flows, and so on.  The result is that, if a large
number of packets that need flow setups come in all at once, then some of
them can overflow the relatively small kernel-to-user buffers.

This commit increases the kernel-to-user buffers from the default of
approximately 120 kB each to 1 MB each.  In one somewhat synthetic test
case that I ran based on an "hping3" that generated a load of about 20,000
new flows per second (including both requests and replies), this reduced
the packets dropped at the kernel-to-user interface from about 30% to none.
I expect that it will similarly improve packet loss in workloads where
flow arrival is not easily predictable.

(This has little effect on workloads generated by "ovs-benchmark rate"
because that benchmark is effectively "self-clocking", that is, a new flow
is triggered only by a reply to a request made earlier, which means that
the number of buffered packets at any given has a known, constant upper
limit.)

Bug #10210.
Signed-off-by: Ben Pfaff <blp@nicira.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/include/sparse/sys/socket.h b/include/sparse/sys/socket.h
index 89e3c2dc2..1ed195b25 100644
--- a/include/sparse/sys/socket.h
+++ b/include/sparse/sys/socket.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011 Nicira Networks.
+ * Copyright (c) 2011, 2012 Nicira Networks.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -74,7 +74,8 @@ enum {
     SO_SNDBUF,
     SO_SNDLOWAT,
     SO_SNDTIMEO,
-    SO_TYPE
+    SO_TYPE,
+    SO_RCVBUFFORCE
 };
 
 enum {