throughput and interrupts

Bachilo Dmitry root at
Wed Aug 16 03:23:12 UTC 2006

В сообщении от Вторник 15 августа 2006 19:02 Robert Watson написал(a):
> On Tue, 15 Aug 2006, Bachilo Dmitry wrote:
> > I am completely stuck. I have a router, that rules three subnets. At
> > first there were Allied Telesyn's netcards with realtek chipsets. I am
> > using ipfw+natd and I had like 3,5 megabytes per second with 20 per cent
> > of interrupt load. I had "discarded oversized frame" too often so I've
> > replaced two main cards with 3Com 905 and now my xl0 and xl1 never
> > discard frames. But I saw no speed boost and interrupts were also very
> > high. I have discovered some IRQ conflicts and removed them, now I have
> > single device per IRQ, but still i have near 20-30 % of interrupt load,
> > when i download something through this router (and natd takes rest % of
> > CPU). Some people advised me to use polling, so I've built kernel with
> > HZ=1000, polling and tried it. Interrupts grew to 40-50% and speed
> > decreased to 200-300 kb/s, so I had to turn the polling off.
> >
> > I just don't know what to try, to gain at least 9 mb/s, because this is
> > what I get at home with the same cards, the same processor, with no
> > polling and throgh the same provider.

Oh, it's natd. Now I see, but I just don't get it. I know that natd is not 
efficient but, as I've said, at home I have 9 or almost 10 MB/sec through the 
natd, while at this particular server I see only 3,7 MB maximum. I've tried 
now to turn all the natting off and tried to download a file and got like 9 
MB/sec, so it is natd who loads the system up.

Someone advised me to use pf or ipnat, but I never did that before and heard 
that this nats have some limitations (like ipnat can't translate icmp packets 
or something). Furthermore I can't stop using ipfw, so pf is automaticly 
excluded. Maybe there are some more advises? I don't really want to have top 
performance with this router, I just want to raise it a bit, to at least stop 
loosing control on this router while someone is watching movie through it - 
ssh session becomes slow, so I type one letter per minute in this case.

Well, if there is nothing I can do, I will stay with it, things are not that 
bad afterall :-)

С уважением, Бачило Дмитрий
Руководитель отдела системной интеграции
ООО "Компания СоЛинк"

More information about the freebsd-current mailing list