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netlink-socket: Increase Netlink socket receive buffer size.

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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>
This commit is contained in:
Ben Pfaff
2012-03-15 21:15:38 -07:00
parent 33500edd53
commit d2b9f5b017
2 changed files with 12 additions and 3 deletions
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10
lib/netlink-socket.c
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@@ -1,5 +1,5 @@
/*
* Copyright (c) 2008, 2009, 2010, 2011 Nicira Networks.
* Copyright (c) 2008, 2009, 2010, 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.
@@ -89,6 +89,7 @@ nl_sock_create(int protocol, struct nl_sock **sockp)
struct nl_sock *sock;
struct sockaddr_nl local, remote;
socklen_t local_size;
int rcvbuf;
int retval = 0;
if (!max_iovs) {
@@ -122,6 +123,13 @@ nl_sock_create(int protocol, struct nl_sock **sockp)
sock->protocol = protocol;
sock->dump = NULL;
rcvbuf = 1024 * 1024;
if (setsockopt(sock->fd, SOL_SOCKET, SO_RCVBUFFORCE,
&rcvbuf, sizeof rcvbuf)) {
VLOG_WARN_RL(&rl, "setting %d-byte socket receive buffer failed (%s)",
rcvbuf, strerror(errno));
}
retval = get_socket_rcvbuf(sock->fd);
if (retval < 0) {
retval = -retval;