Performance Intel Pro 1000 MT (PWLA8490MT)

[Jon Noack]

On 4/19/2005 1:32 PM, Eivind Hestnes wrote:
> I have an Intel Pro 1000 MT (PWLA8490MT) NIC (em(4) driver 1.7.35) installed
> in a Pentium III 500 Mhz with 512 MB RAM (100 Mhz) running FreeBSD 5.4-RC3.
> The machine is routing traffic between multiple VLANs. Recently I did a
> benchmark with/without device polling enabled. Without device polling I was
> able to transfer roughly 180 Mbit/s. The router however was suffering when
> doing this benchmark. Interrupt load was peaking 100% - overall the system
> itself was quite unusable (_very_ high system load). With device polling
> enabled the interrupt kept stable around 40-50% and max transfer rate was
> nearly 70 Mbit/s. Not very scientific tests, but it gave me a pin point.

The card is plugged into a 32-bit PCI slot, correct?  If so, 180 Mbit/s 
is decent.  I have a gigabit LAN at home using Pro 1000 MTs (in 32-bit 
PCI slots) and get NFS transfers maxing out around 23 MB/s, which is 
~180 Mbit/s.  Gigabit performance with 32-bit cards is atrocious.  It 
reminds me of the old 100 Mbit/s ISA cards...

> <snip>
> 
> HZ set to 1000 as recommended in README for the em(4) driver. Driver is of
> cource compiled into kernel.

You'll need HZ set to more than 1000 for gigabit; bump it up to at least 
2000.  That should increase polling throughput a lot.  I'm not sure 
about other polling parameters, however.

Jon