Do you have other PCI cards in this machine? And - is it equipped with 64bit slot? And is it 66MHz (the PCI bus)
Remember:
To get the full bandwidth on the Gb NIC you need the 66MHz/64bit PCI bus.
The slowest card on the PCI bus determines the SPEED not the WIDTH.
So a 33MHz card on the bus will limit your entire PCi bus to 33MHz.
64/32 bit is on a transaction basis unless you have a bus extender that only does 32 bit.
The speed you should be able to get with this Intel part should be around 750Mb/s assuming a 66MHz/64 bus.
Average speed for Gb NICs are around 350Mb/s
Regards,
Dr. Karsten Jeppesen VP of Technology Total Impact <mailto://kj@totalimpact.com> Tel: 805.987.8704 Fax: 805.484.9469
On Friday, Apr 25, 2003, at 12:13 America/Los_Angeles, John Heffner wrote:
First, if you haven't done so, set the MTU on all your GigE interfaces to
9000. This should help a lot as there's a significant amount of
per-packet overhead. Hopefully your switch supports this.
Also, if you want to take advantage of checksum offloading (doing zero-copy), you'll have to use the sendfile(2) call. There's really no way around this with a sockets API.
-John
On Fri, 25 Apr 2003, Fred Gray wrote:
Dear linux-net,
I have recently taken over the development of the data acquisition system
for a physics experiment. The first layer of this system needs to read data
from custom electronics across a VME backplane at about 15 MB/s and forward
it to a back-end machine for online analysis and storage.
My predecessor invested lots of $$$ in a proprietary interconnection scheme
that has proven to be extremely unstable in actual use. I am trying to replace
it with gigabit Ethernet, but I am having trouble getting acceptable
performance.
The front-end processors are Motorola MVME 2600 boards, which have 200 MHz
PowerPC 604e CPUs. I have equipped them with SBS Technologies PMC-Gigabit-ST3
daughtercards, which use the Intel 82545EM chipset. The PMC (PCI Mezzanine
Connector--just PCI in a different form factor) slot is 66 MHz, 64-bit capable.
I am running a 2.4.21-pre6 kernel from the linuxppc_2_4_devel BK tree,
which includes version 4.4.19-k2 of the e1000 driver. The back-end server
is a 1.7 GHz Pentium 4 with an Intel PRO/1000 T Server Adapter, and they are
connected through a D-Link DGS-1008T gigabit switch.
As measured with netperf and/or ttcp, I get between 80 and 90 Mbps from
the front-end to the back-end server, which is a 1.7 GHz Pentium 4,
even with the socket buffer size and TCP window size set to 256KB.
In other words, I might as well have used the built-in 100BaseT port.
The same benchmarks give around 350 Mbps between the server and another
gigabit-equipped PC connected through the same switch, so I don't think
my test is intrinsically flawed.
While performing these benchmarks, the CPU utilization of netperf on
the front-end is between 90% and 100%, suggesting that the process of
sending the data is CPU-bound. I suppose that it might be occupied with
computing the TCP checksum. The documentation for the 82545EM chipset
claims that it supports transmit checksum offloading, but the Linux e1000
driver does not seem to use this feature, only receive checksum offloading.
Is a 200 MHz PowerPC processor simply not adequate to drive a gigabit link
faster than 80 Mbps, or do I have any options left to try? In our controlled
environment, I could possibly consider hacking the kernel on both ends to
disable checksum computation and verification, but I would certainly prefer
not to have to resort to such extreme measures, and I am in any event not
yet certain that the overhead comes from the checksum. I don't need full
gigabit speed: 150 Mbps would be adequate.
Thanks in advance to the networking gurus for their advice,
-- Fred
-- Fred Gray / Visiting Postdoctoral Researcher --
-- Department of Physics / University of California, Berkeley --
-- fegray@socrates.berkeley.edu / phone 510-642-4057 / fax 510-642-9811 --
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