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Date: Thu, 4 Feb 2016 11:13:24 -0800
From: Rick Jones <rick.jones2@....com>
To: netdev@...r.kernel.org
Subject: Disabling XPS for 4.4.0-1+ixgbe+OpenStack VM over a VLAN means 65%
increase in netperf TCP_STREAM
Folks -
I was doing some performance work with OpenStack Liberty on systems with
2x E5-2650L v3 @ 1.80GHz processors and 560FLR (Intel 82599ES) NICs onto
which I'd placed a 4.4.0-1 kernel. I was actually interested in the
effect of removing the linux bridge from all the plumbing OpenStack
creates (it is there for iptables-based implementation of security group
rules because OS Liberty doesn't enable them on the OVS bridge(s) it
creates), and I'd noticed that when I removed the linux bridge from the
"stack" instance-to-instance (vm-to-vm) performance across a VLAN-based
Neutron private network dropped. Quite unexpected.
On a lark, I tried explicitly binding the NIC's IRQs and Boom! the
single-stream performance shot-up to near link-rate. I couldn't recall
explicit binding of IRQs doing that much for single-stream netperf
TCP_STREAM before.
I asked the Intel folks about that, they suggested I try disabling XPS.
So, with that I see the following on single-stream tests between the
VMs on that VLAN-based private network as created by OpenStack Liberty:
99% Confident within +/- 2.5% of "real" average
TCP_RR in Trans/s TCP_STREAM in Mbit/s
XPS Enabled XPS Disabled Delta
TCP_STREAM 5353 8841 (*) 65.2%
TCP_RR 8562 9666 12.9%
The Intel folks suggested something about the process scheduler moving
the sender around and ultimately causing some packet re-ordering. That
could I suppose explain the TCP_STREAM difference, but not the TCP_RR
since that has just a single segment in flight at one time.
I can try to get perf/whatnot installed on the systems - suggestions as
to what metrics to look at are welcome.
happy benchmarking,
rick jones
* If I disable XPS on the sending side only, it is more like 7700 Mbit/s
netstats from the receiver over a netperf TCP_STREAM test's duration
with XPS enabled:
$ netperf -H 10.240.50.191 -- -o throughput,local_transport_retrans
MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to
10.240.50.191 () port 0 AF_INET : demo
Throughput,Local Transport Retransmissions
5292.74,4555
$ ./beforeafter before after
Ip:
327837 total packets received
0 with invalid addresses
0 forwarded
0 incoming packets discarded
327837 incoming packets delivered
293438 requests sent out
Icmp:
0 ICMP messages received
0 input ICMP message failed.
ICMP input histogram:
destination unreachable: 0
0 ICMP messages sent
0 ICMP messages failed
ICMP output histogram:
destination unreachable: 0
IcmpMsg:
InType3: 0
OutType3: 0
Tcp:
0 active connections openings
2 passive connection openings
0 failed connection attempts
0 connection resets received
0 connections established
327837 segments received
293438 segments send out
0 segments retransmited
0 bad segments received.
0 resets sent
Udp:
0 packets received
0 packets to unknown port received.
0 packet receive errors
0 packets sent
IgnoredMulti: 0
UdpLite:
TcpExt:
0 TCP sockets finished time wait in fast timer
0 delayed acks sent
Quick ack mode was activated 1016 times
50386 packets directly queued to recvmsg prequeue.
309545872 bytes directly in process context from backlog
2874395424 bytes directly received in process context from prequeue
86591 packet headers predicted
84934 packets header predicted and directly queued to user
6 acknowledgments not containing data payload received
20 predicted acknowledgments
1017 DSACKs sent for old packets
TCPRcvCoalesce: 157097
TCPOFOQueue: 78206
TCPOrigDataSent: 24
IpExt:
InBcastPkts: 0
InOctets: 6643231012
OutOctets: 17203936
InBcastOctets: 0
InNoECTPkts: 327837
And now with it disabled on both sides:
$ netperf -H 10.240.50.191 -- -o throughput,local_transport_retrans
MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to
10.240.50.191 () port 0 AF_INET : demo
Throughput,Local Transport Retransmissions
8656.84,1903
$ ./beforeafter noxps_before noxps_avter
Ip:
251831 total packets received
0 with invalid addresses
0 forwarded
0 incoming packets discarded
251831 incoming packets delivered
218415 requests sent out
Icmp:
0 ICMP messages received
0 input ICMP message failed.
ICMP input histogram:
destination unreachable: 0
0 ICMP messages sent
0 ICMP messages failed
ICMP output histogram:
destination unreachable: 0
IcmpMsg:
InType3: 0
OutType3: 0
Tcp:
0 active connections openings
2 passive connection openings
0 failed connection attempts
0 connection resets received
0 connections established
251831 segments received
218415 segments send out
0 segments retransmited
0 bad segments received.
0 resets sent
Udp:
0 packets received
0 packets to unknown port received.
0 packet receive errors
0 packets sent
IgnoredMulti: 0
UdpLite:
TcpExt:
0 TCP sockets finished time wait in fast timer
0 delayed acks sent
Quick ack mode was activated 48 times
91752 packets directly queued to recvmsg prequeue.
846851580 bytes directly in process context from backlog
5442436572 bytes directly received in process context from prequeue
102517 packet headers predicted
146102 packets header predicted and directly queued to user
6 acknowledgments not containing data payload received
26 predicted acknowledgments
TCPLossProbes: 0
TCPLossProbeRecovery: 0
48 DSACKs sent for old packets
0 DSACKs received
TCPRcvCoalesce: 45658
TCPOFOQueue: 967
TCPOrigDataSent: 30
IpExt:
InBcastPkts: 0
InOctets: 10837972268
OutOctets: 11413100
InBcastOctets: 0
InNoECTPkts: 251831
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