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

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

[Daniel J Blueman]

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.

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.

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
-- 
Daniel J Blueman

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

[Stephen Hemminger]

On Tue, 27 Feb 2007 11:31:58 +0000
"Daniel J Blueman" <daniel.blueman@gmail.com> 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 <shemminger@linux-foundation.org>