[BUG] ixgbe: something wrong with queue selection ?

Eric Dumazet
2012-04-17T09:07:03Z

Hi guys

I have bad feelings with ixgbe and its multiqueue selection.

On a quad core machine (Q6600), I get lots of reorderings on a single
TCP stream.

Apparently packets happily spread on all available queues, instead of a
single one.

This defeats GRO at receiver and TCP performance is really bad.

# ethtool -S eth5|egrep "x_queue_[0123]_packets" ; taskset 1 netperf -H
192.168.99.1 ; ethtool -S eth5|egrep "x_queue_[0123]_packets"
tx_queue_0_packets: 24
tx_queue_1_packets: 26
tx_queue_2_packets: 32
tx_queue_3_packets: 16
rx_queue_0_packets: 11
rx_queue_1_packets: 47
rx_queue_2_packets: 27
rx_queue_3_packets: 22
MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to
192.168.99.1 (192.168.99.1) port 0 AF_INET
Recv Send Send
Socket Socket Message Elapsed
Size Size Size Time Throughput
bytes bytes bytes secs. 10^6bits/sec

87380 16384 16384 10.00 3866.43
tx_queue_0_packets: 1653201
tx_queue_1_packets: 608000
tx_queue_2_packets: 541382
tx_queue_3_packets: 536543
rx_queue_0_packets: 434703
rx_queue_1_packets: 137444
rx_queue_2_packets: 131023
rx_queue_3_packets: 128407

# ip ro get 192.168.99.1
192.168.99.1 dev eth5 src 192.168.99.2
cache ipid 0x438b rtt 4ms rttvar 4ms cwnd 57 reordering 127

# lspci -v -s 02:00.0
02:00.0 Ethernet controller: Intel Corporation 82599EB 10-Gigabit
SFI/SFP+ Network Connection (rev 01)
Subsystem: Intel Corporation Ethernet Server Adapter X520-2
Flags: bus master, fast devsel, latency 0, IRQ 16
Memory at f1100000 (64-bit, prefetchable) [size=512K]
I/O ports at b000 [size=32]
Memory at f1200000 (64-bit, prefetchable) [size=16K]
Capabilities: [40] Power Management version 3
Capabilities: [50] MSI: Enable- Count=1/1 Maskable+ 64bit+
Capabilities: [70] MSI-X: Enable+ Count=64 Masked-
Capabilities: [a0] Express Endpoint, MSI 00
Capabilities: [100] Advanced Error Reporting
Capabilities: [140] Device Serial Number 00-1b-21-ff-ff-4a-fe-54
Capabilities: [150] Alternative Routing-ID Interpretation (ARI)
Capabilities: [160] Single Root I/O Virtualization (SR-IOV)
Kernel driver in use: ixgbe
Kernel modules: ixgbe