70% of packet loss with em(4) and ti(4) due to interrupts

[Jedi/Sector One <obsd-misc_(_at_)_pureftpd_(_dot_)_org>]

  Hello.
  
  I'm facing a nasty issue with gigabit firewalls (only two interfaces)
running OpenBSD 3.6-stable. pf is not the culprit since disabling it
doesn't change anything.
  
  The NICs are generating too many interrupts. With ti(4) I have about 40%
packet loss when 300 Mb/s is reached. With em(4) I have 70% of packet loss
and there's of course no way to go past 300 Mb/s. This is with 1000baseSX.

  99% of the system load is due to interrupts.

  Is there anything I may do in order to improve the situation? Would faster
or SMP machines help?

  Best regards,

-- 
Frank - my stupid blog: http://00f.net