Start irqbalance by default

[Martin Pitt]

Hello all,

Steve Langasek [2010-01-08 20:14 -0800]:
>  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.

To be honest, this sounds a bit like black voodoo to me. How can it be
more efficient to schedule interrupts in an userspace daemon than in
the kernel itself (where it is already done presumably)? Does
userspace have more information about which processes are running and
what they are going to do? If so, doesn't that involve more IPC and
thus wakeups? If not, why isn't that alternative strategy implemented
in the kernel itself (right now it seems that the scheduling would be
done at two places?)

>  - 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?

That's my primary concern, too. Do we have some measurements about
this?

Chuck, did you actually intend to install this on all desktop systems
as well, or just servers (where performance might matter more).

Thanks,

Martin

-- 
Martin Pitt                        | http://www.piware.de
Ubuntu Developer (www.ubuntu.com)  | Debian Developer  (www.debian.org)
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