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SubjectNAPI and tg3
Hi guys,

I have access to 8 Dell 2650s with onboard Broadcom BCM5701 chips. They
are quipped with Dual 2.4 GHz Xeon processors and 1GB of RAM. I'm running
RedHat 7.3, but with a stock 2.4.20 kernel.

As I understand it the tg3 driver is using NAPI on the 2.4.20 kernel
(dev->poll). I've been experiencing bad performance (low bandwidth) on
cluster applications running with LAM for example, but the problem
manifest itself if you run two bandwidth needy applications in parallel
on two machines (i.e two processes on each machine, one per processor)
using Gbe.

I've disabled the NAPI mode and went back to the old interrupt method and
this works much better (i.e the bandwidth is now evenly distributed
between the two applications).

What could be the cause of this problem ? Is it NAPI itself (doing RX
under scheduler control) or is it something else (for example lock
contetion).

Any ideas ?

Thanks,
--
Steffen Persvold | Scali AS
mailto:sp@scali.com | http://www.scali.com
Tel: (+47) 2262 8950 | Olaf Helsets vei 6
Fax: (+47) 2262 8951 | N0621 Oslo, NORWAY


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