tuning for high connection rates

Philipp Wuensche cryx-freebsd at h3q.com
Wed Dec 5 07:03:31 PST 2007

Adrian Chadd wrote:
> On 05/12/2007, Philipp Wuensche <cryx-freebsd at h3q.com> wrote:
>> As I understand it, and correct me if I'm wrong, polling helps against
>> high interrupt rates but for that intel gigabit cards have interrupt
>> moderation. We don't have a problem with interrupts (20% CPU) at the
>> moment but with system (100% CPU) as you can see in the system
>> monitoring graphs. Interrupts sometimes peak at, but usually are under,
>> the 2k interrupts/sec limit.
> Begin by reading up on the hardware profiling support (hwpmc, pmc,
> etc) and see if you can get some system and process-specific profiling
> information.

Oh interesting stuff, I definitely have to take a look into that. Nice.

> Kernel/System profiling will probably show you an interesting thing or
> two. One thing I noticed was high in my high-TCP-transaction tests
> (but not on hardware anywhere near as nice as yours!) was crypto calls
> for, IIRC, syncookies.

We tried with syncookies enabled and disabled, no change at all. But as
you already said, crypto calls on this kind of hardware are not that
expensive ;-)


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