Re: Observations on LG_NAS, mvgbe0 issue?

[Reinoud Zandijk <reinoud%NetBSD.org@localhost>]

On Tue, Jul 02, 2013 at 11:49:43AM +0100, Robert Swindells wrote:
> Reinoud Zandijk <reinoud%NetBSD.org@localhost> wrote:
> >If I test it from another machine and read the same set from NFS i get
> >quite different values! The rate drops to 11 Mb/sec and the system
> >time is around 30% but the interrupt time is 60-70%!
> 
> How fast is the NFS server ?

Well this NAS is also my NFS server :) the client is an i7 amd machine so
thats not really a factor to account for in this.

> >Am I right to conclude that the Marvell Gbit ethernet controller
> >mvgbe0 is NOT using DMA? or is it using it but also crappy in design?
> 
> Not really, the ethernet controller holds pointers to buffers in memory
> and raises an interrupt either when they have all been filled or when a
> tuneable timer expires.
> 
> I don't know if we have done very much testing on how many packets it
> can batch together in one interrupt.

I doubt its batching at all creating so many interrupts and consuming so much
interrupt time. I also tested the machine on a 100 mbit network but the result
is the same as the network is quite quiet normally other than some spurious
http and mail work next to some mild NFS.

Reinoud