amrd disk performance drop after running under high load

[Alexey Popov]

Hi

Scott Long wrote:

>>> interrupt                          total       rate
>>> irq6: fdc0                             8          0
>>> irq14: ata0                           47          0
>>> irq16: uhci0                  1428187319       1851
>>                                 ^^^^^^^^^^       ^^^^ [1]
>>> irq18: uhci2                    12374352         16
>>> irq23: ehci0                           3          0
>>> irq46: amr0                     11983237         15
>>> irq64: em0                    1427141755       1850
>>                                 ^^^^^^^^^^       ^^^^ [2]
>>> cpu0: timer                   1540896452       1997
>>> cpu1: timer                   1542377798       1999
>>> Total                         5962960971       7730
>>
>> [1] and [2] looks suspicious to me (totals and rate are too close to
>> each other and btw to timers). Let the latter (timers) alone. Do you
>> use any USB device? Can you try to use other network card? That
>> behaviour seems to be an interrupt storm and/or irq collision.
> 
> It's neither.  It's a side effect of a feature that FreeBSD abuses for
> handling interrupts.  Note that amr0 and ehci2 are acting similar.  It's
> mostly harmless, but it does waste CPU cycles.  I wouldn't expect this
> on a recent version of FreeBSD, though, at least not from the e1000
> driver.
I have this effect on many servers and I believe it is harmless. At once 
I was trying to reduce CPU usage on the very loaded server and removed 
USB from kernel. This effect disappeared, but there was no significant 
difference in CPU usage.

I disagree about your words about recent version. I have this effect on 
many servers with latest FreeBSD-6-stable and em. Actually I have more 
servers with this effect than without it.

With best regards,
Alexey Popov