Re: disabling interrupt storm protection

On Thursday 28 October 2004 06:13 am, Shunsuke SHINOMIYA wrote:
>  Thank you, John.
>
> > Can you try this patch:
> >
> > --- //depot/vendor/freebsd/src/sys/kern/kern_intr.c	2004/09/05 02:10:52
> > +++ //depot/projects/smpng/sys/kern/kern_intr.c	2004/10/27 17:41:06
>
>  snip
>
> > First, can you test that your system works with the default threshold,
> > and second, can you test that setting the threshold to zero disables the
> > storm detection?
>
>  I applied your patch to kern_intr.c, and then I transmitted the high
>  rate(148kpps) IP traffic to the box with the default threshold. But
>  storm protection was not invoked.
>
>  It seem that sensitivity of the detector is fallen.
>
>  I tried some patterns of the packet loss test(transmitting the packets
>  of the wire rate in 100Mbps to the box for 10 seconds.  The frame size
>  of each packets is 64 octet).
>
>  These results are as follows.
>
>  Each `before' and `after' are outputs of `vmstat -i | grep em'. Please
>  observe the first numerical value(number of interrupts since system
>  startup). kern.hz is 100 at all trials. And `Interrupt Moderation', one
>  of the feature of em was disabled.
>
> ==========
> o kern_intr.c applied your patch.
> o hw.intr_storm_threshold=500(default)
>
> remark
>  o The test results of both 1st and 2nd trial are good, low packet loss
>  rate. A difference of both trials may be measurement error.
>  o Interrupt storm protections is not invoked.
>  o The interrupts rate of em0(input side) is about 25000 interrupts per
>  second during a trial.
>  o When hw.intr_storm_threshold=200, Interrupt storm protections is not
>  invoked.

Excellent, thanks.  I feared that the stuff under #ifdef HACK was causing 
false positives.  I'll revert the code to the non-HACK version in HEAD and 
will get it into RELENG_5 at some point (though it is probably too late for 
5.3.)

-- 
John Baldwin <jhb_at_FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org