netdev - Re: Horrid balance-rr bonding udp throughput

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Date:   Mon, 10 Apr 2017 12:11:11 -0700
From:   Ben Greear <greearb@...delatech.com>
To:     Jarod Wilson <jarod@...hat.com>, netdev <netdev@...r.kernel.org>
Subject: Re: Horrid balance-rr bonding udp throughput

On 04/10/2017 11:50 AM, Jarod Wilson wrote:
> On 2017-04-08 7:33 PM, Jarod Wilson wrote:
>> I'm digging into some bug reports covering performance issues with balance-rr, and discovered something even worse than the reporter. My test setup has a pair
>> of NICs, one e1000e, one e1000 (but dual e1000e seems the same). When I do a test run in LNST with bonding mode balance-rr and either miimon or arpmon, the
>> throughput of the UDP_STREAM netperf test is absolutely horrible:
>>
>> TCP: 941.19 +-0.88 mbits/sec
>> UDP: 45.42 +-4.59 mbits/sec
>>
>> I figured I'd try LNST's packet capture mode, so exact same test, add the -p flag and I get:
>>
>> TCP: 941.21 +-0.82 mbits/sec
>> UDP: 961.54 +-0.01 mbits/sec
>>
>> Uh. What? So yeah. I can't capture the traffic in the bad case, but I guess that gives some potential insight into what's not happening correctly in either
>> the bonding driver or the NIC drivers... More digging forthcoming, but first I have a flooded basement to deal with, so if in the interim, anyone has some
>> insight, I'd be happy to hear it. :)
>
> Okay, ignore the bit about bonding, I should have eliminated the bond from the picture entirely. I think the traffic simply ended up on the e1000 on the
> non-capture test and on the e1000e for the capture test, as those numbers match perfectly with straight NIC to NIC testing, no bond involved. That said, really
> odd that the e1000 is so severely crippled for UDP, while TCP is still respectable. Not sure if I have a flaky NIC or what...
>
> For reference, e1000 to e1000e netperf:
>
> TCP_STREAM: Measured rate was 849.95 +-1.32 mbits/sec
> UDP_STREAM: Measured rate was 44.73 +-5.73 mbits/sec

Maybe check that you have re-ordering issues?  I ran into that with igb
recently and it took a while to realize my problem!

Thanks,
Ben

-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com