Re: poor gigabit ethernet performance with amd64 + sk0

Quoting Dan Nelson <dnelson_at_allantgroup.com>:

> In the last episode (Mar 25), Kenneth Culver said:
>> I recently did a short file transfer over gigabit ethernet in both
>> x86 and amd64. On x86 it appears the limiting factor is the laptop
>> I'm transferring to. I get about 20MB/sec to the laptop in x86. But
>> on amd64, I'm not sure what the limiting factor is, because I max out
>> at about 2.8MB/sec with the EXACT same hardware. Here are the dmesg
>> lines for that ethernet card:
>
> Make sure you're testing ethernet speeds and not disk speeds; try
> something like ttcp or tcpblast.  Even a pII/600mhz can do 50MB/sec;
> any modern CPU should be able to do 90.  You might also want to do a
> long test, then run systat -v to see if the CPU load or interrupts/sec
> is different between x86 and amd64 modes.
>
> --
> 	Dan Nelson
> 	dnelson_at_allantgroup.com

I know for sure I'm not testing disk speeds, at least on the x86 side. In x86
the transfer at 20MB/sec is maxing out my laptop's hard drive. I have the same
model hard drive running my amd64 -CURRENT as I do my x86 -CURRENT, and both
kernels were built from the same source tree. The only difference I see when
running the tests with systat -vm 1 is that sk0 is only interrupting around
600-800 times per second on amd64, where it's interrupting at like 4000 times
per second on x86, which is what I'd expect given that on FreeBSD-x86 I'm
sending data at 10x the speed of FreeBSD-amd64.

One other thing I noticed while doing the systat -vm 1 was that the clk device
is interrupting at over 1000 times per second instead of the x86'x 100 times
per second. I could try changing that to 100 and see what happens. Also I'm
read a little bit in the NOTES file on amd64 that atpic is for legacy 8259A
interrupt controller support. I don't think I need that either. Could any of
these be causing my problem?

Ken