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SubjectRe: [PATCH 2.6.30-rc4] r8169: avoid losing MSI interrupts
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On Sat, 2009-05-23 at 16:35 +0200, Michael Riepe wrote:
> Hi!
>
> Michael Buesch wrote:
>
> > Thanks a lot, Dave! This fixes the issue on my chip.
>
> Yep, it's stable here as well. And even a little faster than pci=nomsi.
> The only strangeness I observed is that the throughput (measured with
> iperf and a single TCP connection) varies:
>
> [ ID] Interval Transfer Bandwidth
> [ 3] 0.0-10.0 sec 667 MBytes 559 Mbits/sec
> [ 3] 10.0-20.0 sec 803 MBytes 673 Mbits/sec
> [ 3] 20.0-30.0 sec 802 MBytes 673 Mbits/sec
> [ 3] 30.0-40.0 sec 714 MBytes 599 Mbits/sec
> [ 3] 40.0-50.0 sec 669 MBytes 561 Mbits/sec
> [ 3] 50.0-60.0 sec 791 MBytes 663 Mbits/sec
> [ 3] 0.0-60.0 sec 4.34 GBytes 622 Mbits/sec
>
[snip]
> I suppose it's a side effect of the MSI acknowledgement loop. But who am
> I to complain about higher average throughput? ;-)

I wonder if that is the TCP sawtooth pattern -- run up until we drop
packets, drop off, repeat. I thought newer congestion algorithms would
help with that, but I've not kept up, this may be another red-herring --
like the bisection into genirq.

A tcpdump may answer the question -- wireshark can do an analysis and
see if it is running up until it starts dropping or something.

Or it may be the loop, but I wouldn't expect it to make such a big
difference, or be as variable if it does.
Also, what does it look like with multiple streams?

Thanks for testing guys -- I'm glad it works for a sample size > 1!
Dave



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