Subject: Re: NAPI, e100, and system performance problem

From: Andi Kleen <[email-masked]>
Date: Fri, 22 Apr 2005 13:36:56 +0200

Greg Banks <[email-masked]> writes:
>
> An inordinate amount of CPU is being spent running around polling the
> device instead of dealing with the packets in IP, TCP and NFS land.
> By inordinate, we mean twice as much or more cpu% than a MIPS/Irix
> box with slower CPUs.

We have seen similar behaviour. With NAPI some benchmarks run
a lot slower than on a driver on the same hardware/NIC without NAPI.
This can be even observed with simple tests like netperf single stream
between two boxes.

There seems to be also some problems with bidirectional traffic, although
I have not fully tracked them down to NAPI yet.

There is definitely some problem in NAPI land ...

-Andi