Re: [BUG] ixgbe: something wrong with queue selection ?

Eric Dumazet
2012-04-17T16:46:50Z

On Tue, 2012-04-17 at 09:01 -0700, Alexander Duyck wrote:
> On 04/17/2012 02:16 AM, Jeff Kirsher wrote:
> > On Tue, 2012-04-17 at 11:06 +0200, Eric Dumazet wrote:
> >> 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
> >>
> >>
> > Adding Don Skidmore and Alex Duyck...
> This is probably the result of ATR and the load balancer on the system.
> What is likely happening is that the netperf process is getting moved
> from CPU to CPU, and this is causing the transmit queue to change. Once
> this happens the ATR will cause the receive queue to change in order to
> follow the transmitting process.
>
> One thing you might try is using the "-T" option in netperf to see if
> the behaviour occurs if the process is bound to a specific CPU. Another
> thing you might try would be to disable ATR by enabling ntuple. You
> should be able to do that with "ethtool -K eth5 ntuple on".

I used taskset 1 netperf, to force netperf running on cpu0.

Problem is incoming ACKs seem to be spreaded, so TCP stack might run on
all cpus.