tuning for high connection rates

Philipp Wuensche cryx-freebsd at h3q.com
Wed Dec 5 15:03:02 PST 2007

Mike Tancsa wrote:
> At 05:19 PM 12/5/2007, Philipp Wuensche wrote:
>> After switching to net.isr.direct=0 and 346609775 good packets later, RX
>> overruns haven't increased by one! Thats nice. Still interrupt is using
>> up the CPU. I'm not quite sure if polling would help now!?
> Polling is helpful to prevent livelock. Not sure if thats happening to
> you.  

No problems with livelock, system is usable all the time.

> What firewall (if any) are you using ?  pf used to be a lot slower
> than ipfw.

We use pf. Disabling it at all gives no noticable performance boost
because instead performance drops due to connections from networks we
currently filter. Maybe ipfw is faster, we could try that but would like
to use pf furthermore.

> Another thing to try is to turn back on Fast Interrupt handling. I think
> its currently disabled.
> In if_em.h, try adding
> #define EM_FAST_IRQ 1
> and then recompile the kernel or just driver.

Seems to be enabled by default on freebsd7, from our if_em.h:

/* Set FAST handling on by default */
#if __FreeBSD_version > 700000
#define EM_FAST_IRQ


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