Re: Broadcom 5700/5701 Gigabit Ethernet Adapters

Michael Clark
2002-03-11T04:20:52Z

On Monday, March 11, 2002, at 11:15 AM, Benjamin LaHaise wrote:

> On Sun, Mar 10, 2002 at 06:30:33PM -0800, David S. Miller wrote:
>> Syskonnect sk98 with jumbo frames gets ~107MB/sec TCP bandwidth
>> without NAPI, there is no reason other cards cannot go full speed as
>> well.
>>
>> NAPI is really only going to help with high packet rates not with
>> thinks like raw bandwidth tests.
>
> Well, the thing that hurts the 83820 is that its interrupt
> mitigation capabilities are rather limited. This is where napi
> helps: by turning off the rx interrupt for the duration of packet
> processing, cpu cycles aren't wasted on excess rx irqs.
>
> As to the lack of bandwidth, it stems from far too much interrupt
> overhead and the currently braindead attempt at irq mitigation.
> Since the last time I worked on it, a number of potential techniques
> have come up that should bring it into the 100MB realm (assuming it
> doesn't get trampled on by ksoftirqd).

What about jumbo frames? I notice this comment in the driver "disable
jumbo frames to avoid tx hangs". I'm getting ~550Mb/sec from a single
TCP stream and ~700Mb/sec with 2 in parallel. Jumbo frames would
probably improve this quite a bit.

~mc