softclock swis not bound to specific cpu
Robert Watson
rwatson at FreeBSD.org
Mon Oct 19 15:05:42 UTC 2009
On Sun, 18 Oct 2009, Taku YAMAMOTO wrote:
> I noticed that the softclock threads didn't seem to be bound to any cpu.
>
> I'm not sure whether it's the Right Thing (TM) to bind them to the
> corresponding cpus though: it might be good to give the scheduler a chance
> to rebalance callouts.
>
> I'm about to test the modification like the attached diff. Comments are
> welcome.
Yes, I think the intent is that they have a "soft" affinity to the CPU where
the lapic timer is firing, but not a hard binding, allowing them to migrate if
required. It would be interesting to measure how effective that soft affinity
is in practice under various loads -- presumably the goal would be for the
softclock thread to migrate if a higher (lower) priority thread is hogging the
CPU.
Robert N M Watson
Computer Laboratory
University of Cambridge
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