Subject: Re: [RFC] irqbalance: Mark in-kernel irqbalance as obsolete, set to N by default

From: Arjan van de Ven <[email-masked]>
Date: Fri, 04 Aug 2006 07:36:06 -0700

Andrew Morton wrote:
> On Mon, 31 Jul 2006 10:35:26 -0700
> Auke Kok <[email-masked]> wrote:
> 
>> We've recently seen a number of user bug reports against e1000 that the 
>> in-kernel irqbalance code is detrimental to network latency. The algorithm 
>> keeps swapping irq's for NICs from cpu to cpu causing extremely high network 
>> latency (>1000ms).
> 
> What kernel versions?  Some IRQ balancer fixes went in shortly after 2.6.17.
> 
> It would be better if poss to fix the balancer rather than deprecating it.

to some degree the in kernel balancer cannot really make the level of decisions that a
userspace balancer can make, at least not without making all kernel developers vomit ;)
(for example the userspace balancer looks in /proc/interrupts and parses that to see
which interrupts are used by networking versus which by storage etc, and has different
balancing policies for those and other classes; the networking policy basically comes down to
"pin the interrupt unless some higher networking interrupt really gets in the way")