Re: sky2 stable in 2.6.12-rc1 (but still performance problem)...

On Tue, 27 Feb 2007 11:31:58 +0000
"Daniel J Blueman" [off-list ref] wrote:

Hi Stephen,

2.6.21-rc1 is the first kernel where my SysKonnect Yukon 2 hardware
with the sky2 v1.13 driver is stable under moderate load. Before a few
GBs of data going over my GigE network quickly with NFSv4 would cause
transmit timeouts previously, but now fine.

I am still observing a performance problem - feels like a wmb() or
some buffer flushing is missing somewhere - disabling processor clock
scaling reduces the problem a bit, but does not eliminate it.

That seems odd, if it was a missing barrier you would see data corruption.
Are there checksum errors?

You might be seeing hardware flow control. Look at ethtool -S eth0 output.
Previously, transmit flow control was broken

What are your preferred way of checking performance? I think that the
TCP send window can grow enough even if ACKs are delayed due to this
problem, such that TCP does not immediately demonstrate this issue. I
could restrict the window scaling factor, so it would be bound by the
data->ACK round-trip latency, which /should/ be low, but I've been
observing it higher. Maybe I try this.

iperf is easiest.

I'll see what I get with iperf UDP also, since this shows min, max,
avg UDP packet latency IIRC.

Thanks for your great work so far though!
  Dan

-- 
Stephen Hemminger [off-list ref]