Re: Although CONFIG_IRQBALANCE is enabled IRQ's don't seem to be balanced very well

[Martin Bligh <mbligh@mbligh.org>]

Jesper Juhl wrote:
> On 1/10/06, Martin Bligh <mbligh@mbligh.org> wrote:
> 
>>Josef Sipek wrote:
>>
>>>On Tue, Jan 10, 2006 at 12:14:42PM +0100, Jesper Juhl wrote:
>>>
>>>
>>>>Do I need any userspace tools in addition to CONFIG_IRQBALANCE?
>>>
>>>
>>>Last I checked, yes you do need "irqbalance" (at least that's what
>>>the package is called in debian.
>>
>>Nope - you need the kernel option turned on OR the userspace daemon,
>>not both.
>>
> 
> Ok, good to know.
> 
> 
>>If you're not generating interrupts at a high enough rate, it won't
>>rotate. That's deliberate.
>>
> 
> 
> Hmm, and what would count as "a high enough rate"?
> 
> I just did a small test with thousands of  ping -f's through my NIC
> while at the same time giving the disk a good workout with tons of
> find's, sync's & updatedb's - that sure did drive up the number of
> interrupts and my load average went sky high (amazingly the box was
> still fairly responsive):
> 
> root@dragon:/home/juhl# uptime
>  22:59:58 up 12:43,  1 user,  load average: 1015.48, 715.93, 429.07
> 
> but, not a single interrupt was handled by CPU1, they all went to CPU0.
> 
> Do you have a good way to drive up the nr of interrupts above the
> treshhold for balancing?

Is it HT? ISTR it was intelligent enough to ignore that. But you'd
have to look at the code to be sure.

M.