softclock swis not bound to specific cpu
ivoras at freebsd.org
Mon Oct 19 15:20:06 UTC 2009
Ivan Voras wrote:
> Robert Watson wrote:
>> 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.
> So why are there NCPU softclock threads if the binding isn't important?
Nevermind, I got it - they are not used only for "clock".
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