[ovs-git] Open vSwitch: netlink-socket: Increase Netlink socket receive buffer size. (branch-1.6)

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commit d195b2f49b0ddfec8a65aa1a7b7336e8c6938d64
Diffs: http://openvswitch.org/cgi-bin/gitweb.cgi?p=openvswitch;a=commitdiff;h=d195b2f49b0ddfec8a65aa1a7b7336e8c6938d64
Author: Ben Pfaff <blp at nicira.com>
		
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 at nicira.com>


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Summary of changes:
 include/sparse/sys/socket.h |    5 +++--
 lib/netlink-socket.c        |   10 +++++++++-
 2 files changed, 12 insertions(+), 3 deletions(-)


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