FreeBSD 5.4+SMP, severe network degredation

[dpk]

Woah. Well, I guess I didn't try *everything*. Removing "device acpi" from
the kernel config leaves me witih a PAE+SMP kernel that works fine. I can
fetch files at wire speed and everything.

So, I guess this issue is closed. acpi was the ultimate culprit.

On Thu, 28 Jul 2005, dpk wrote:

> By the way, I also compared GENERIC performance against GENERIC w/
> "options SMP" added, and had the same results.
>
> On Wed, 27 Jul 2005, dpk wrote:
>
> > We just received several SuperMicro servers, 3.0Ghz Xeon x 2, 4GB RAM.
> > They're using the em driver and the ports are set to 1000Mbit (we also
> > tried 100Mbit/full duplex on the card and on the switch). They're running
> > FreeBSD 5.4.
> >
> > I ran a steady ping on a couple of them while they were running "GENERIC",
> > and then rebooted them with a kernel built with the "PAE" kernel included
> > with the installation, with "option SMP" added.
> >
> > The PAE-SMP-GENERIC kernel was built after cvsup'ing with "tag=RELENG_5_4"
> > and the uname reports "5.4-RELEASE-p5".
> >
> > Here are the ping results:
> >
> > GENERIC:
> >
> > 117 packets transmitted, 117 packets received, 0% packet loss
> > round-trip min/avg/max/stddev = 0.451/0.554/0.856/0.059 ms
> >
> > PAE-SMP-GENERIC:
> >
> > 102 packets transmitted, 102 packets received, 0% packet loss
> > round-trip min/avg/max/stddev = 0.569/4.262/7.944/2.065 ms
> >
> > Fetching a 637MB ISO from a local server, also on 100/FDX:
> >
> > GENERIC:
> >
> > /dev/null                                     100% of  637 MB   10 MBps 00m00s
> >
> > real    0m58.071s
> > user    0m1.954s
> > sys     0m6.278s
> >
> > PAE-SMP-GENERIC:
> >
> > /dev/null                                     100% of  637 MB 5764 kBps 00m00s
> >
> > real    1m53.324s
> > user    0m1.478s
> > sys     0m5.624s
> >
> > Running GENERIC, systat shows about 7000 interrupts/second, and around 600
> > interrupts/second using PAE-SMP-GENERIC, while fetch was running.
> >
> > I've checked the errata and hardware notes, as well as gnats, and was not
> > able to find anything that explains or matches this behavior. We've run
> > SMP servers for years, using 4.5-4.11, but we've never seen the network
> > performance cut in half (or pings go up 10x).
> >
> > Removing "option SMP" makes the problem go away, but at a very significant
> > performance cost obviously.
> >
> > Could it be something from -p5? Is this explained/examined in a PR I've
> > missed, and if so can I add some information?
> >
>