Start irqbalance by default

Steve Langasek steve.langasek at
Sat Jan 9 04:14:47 GMT 2010

Hi Chuck,

On Fri, Jan 08, 2010 at 09:00:12AM -0500, Chuck Short wrote:

> Recently there was some work done to get irqbalance promoted into main. 
> I am looking for people's opinions to see if it should be started by 
> default.

Thanks for bringing up this question.

For context, the irqbalance package is:

 Description: Daemon to balance interrupts for SMP systems
  Daemon to balance interrupts across multiple CPUs, which can lead to
  better performance and IO balance on SMP systems. This package is
  especially useful on systems with multi-core processors, as interrupts
  will typically only be serviced by the first core.
  Note: irqbalance is not useful if you dont have more than one core
        or socket.

Since this means running an extra daemon by default on everyone's systems, I
think the relevant questions are:

 - How much is the CPU overhead resulting from running the daemon in the
   event that there's only one core?
 - Are there downsides to running irqbalance on SMP systems - e.g., does
   using both CPUs for IRQs mean waking up processors that otherwise would
   be allowed to sleep, resulting in more power usage on systems where
   performance is not the primary concern?
 - Does the daemon behave sensibly at startup - minimal CPU usage, and
   starts late in the boot sequence so that it doesn't impact boot
   performance to desktop?
 - (optional) Do we have any estimates (e.g., from the hardware database)
   of the percentage of UP vs. SMP systems these days?

At least the package size shouldn't be a problem if we add this to the
install media - 128k installed, 20k packed.

Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
Ubuntu Developer                          
slangasek at                                     vorlon at
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