Re: Observations on LG_NAS, mvgbe0 issue?

[Robert Swindells <rjs%fdy2.co.uk@localhost>]

Reinoud Zandijk <reinoud%NetBSD.org@localhost> wrote:
>For my LG-NAS, a Marvell based board, the DMA controller is working
>and i can get a rough 27 Mb/sec reading directory trees from the disc
>in FFS and around 90 to 100 Mb/sec from the raw partiton to
>/dev/null. In these i see hardly interrupt time but lots of system
>time, around 70-80% and some 10-15% idle time. So DMA for the SATA is
>working fine! The 70-80% cpu time is most likely FFS, overhead and
>such and some for the /dev/null writing.
>
>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 ?

>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.

Robert Swindells