irqbalance on HT capable PE4600?

Arjan van de Ven arjanv at
Sat Oct 18 03:27:00 CDT 2003

On Sat, Oct 18, 2003 at 12:03:20PM +1000, jason andrade wrote:
> On Wed, 15 Oct 2003, Arjan van de Ven wrote:
> > > Will this lead to better performance?
> >
> > unless you have extreme loads I doubt you can measure the difference.
> > quick rule-of-thumb:
> > if the "irq rate" in "vmstat 1" output is below about 1000 most of the
> > time then you won't find any difference.
> if the irq rate is > 20,000 can you make any comments on things to do
> to provide (marginal?) performance improvements ?  context switches are
> between 20-25,000 also.

First of all; several network cards have ways of
reducing the irq rate via so called interrupt mitigation; this is not
always enabled since it CAN reduce network performance
on low-use networking.
For example, e1000 has several module parameters to enable this:
parm:        TxIntDelay 	description "Transmit Interrupt Delay"
parm:        TxAbsIntDelay 	description "Transmit Absolute Interrupt Delay"
parm:        RxIntDelay 	description "Receive Interrupt Delay"
parm:        RxAbsIntDelay 	description "Receive Absolute Interrupt Delay"

setting these values to > 0 (eg somewhere between 2 and 10) will
probably reduce your rate of interrupts quite significant (and
increase performance due to better irq grouping)

Another thing you can do is install the RHL8 erratum or RHL9
kernel-utils rpm and make sure the irqbalance service is started during
boot (default for RHL9, the RHL8 erratum defaults to off)

    Arjan van de Ven

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