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Date:      Tue, 23 Oct 2012 15:57:01 -0700
From:      Garrett Cooper <yanegomi@gmail.com>
To:        freebsd-net@freebsd.org
Cc:        Jack F Vogel <jfv@freebsd.org>
Subject:   ixgb TSO performance degrades by ~30% between 7.4 and 8.2/9.0/9.1
Message-ID:  <CAGH67wTjVw8O7i9OCvHVJjVjCAXsNHNhs0LobDi4G9iukgf%2BeQ@mail.gmail.com>

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Hi,

Doing some poking around at the ixgb driver with a card I have at
$work using netperf and two machines hooked up over crossover, I
discovered that while ixgb's throughput performance was fantastic on
7.3/7.4, thoughput performance of the card is degraded on 8.2/9.0/9.1
by ~30% (9400Mbps on 7.4 -> 6294Mbps on 9.0 for example). LRO
performance on the other hand is fantastic and doesn't degrade with
the card across FreeBSD versions. Performance remains constant with
ixgb across 8.2/9.0/9.1. I didn't observe the CPU usage.

More details:

The machines are hooked up in the following configuration:

 -----------------------                                 --------------------
| Machine 1 | cxgb | <- 10Gbit fibre -> | ix1 | Machine 2 |
 -----------------------                                ---------------------

Machine Configuration:

The card in Machine 2 is an 82599EB card according to pciconf -lv.

/boot/loader.conf tunables (most of these are set according to 9.x
defaults in order to establish a sane baseline):

kern.ipc.nmbjumbo9=262144
kern.ipc.nmbjumbo16=262144
kern.ipc.nmbclusters=262144
kern.ipc.nmbjumbop=262144
kern.ipc.maxsockbuf=2097152

/etc/sysctl.conf tunables:

net.inet.tcp.recvspace=65536
net.inet.tcp.recvspace_inc=16384
net.inet.tcp.recvspace_max=2097152
net.inet.tcp.sendspace=32768
net.inet.tcp.sendbuf_max=2097152
net.inet.tcp.sendbuf_inc=8192

Kernel Config:

Machine 1 is running a custom version of FreeBSD. The version has been
constant over the course of my testing. Can give vague details on the
config, but can't give some specific details.
Machine 2 is running 7.4/8.2/9.0/9.1 with a GENERIC kernel.

Networking configuration:

- Machine 1 has an IPv4 address of 10.10.10.1; IPv6 is not configured.
The interface mtu is 1500.
- Machine 2 has an IPv4 address of 10.10.10.2; IPv6 is not configured.
The interface mtu is 1500.

Netperf configuration:

- netserver is run on both machines; I don't add any additional
arguments to the netserver invocation so it just goes off and forks.
- netperf is run like: netperf -cCjt TCP_STREAM -H <IP-ADDRESS>

I was wondering if this was a known issue and/or others had seen
similar problems with this card. I haven't gone into profiling the
kernel yet with DTrace, but if no one gets back to me before sometime
later on this week/next week that will be my next course of action for
tracking down the source of the performance problem.

Thanks!
-Garrett



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