[patch] zfs livelock and thread priorities

Attilio Rao attilio at freebsd.org
Mon May 18 17:35:25 UTC 2009

2009/5/18 John Baldwin <jhb at freebsd.org>:
> On Saturday 16 May 2009 12:40:44 pm Ben Kelly wrote:
>>    1) It changes the kproc(9) API by adding a kproc_create_priority()
>> function that allows you to set the priority of the newly created
>> thread.  I'm not sure how people feel about this.
> Actually, I almost think we should just add a priority argument to each of the
> routines that creates a new kthread/kproc.  Perhaps allow a priority of 0 to
> let the thread run with the default priority.  Hmm, it looks like kthreads
> default to running with whatever thread0 runs at (PVM) which is probably not
> really ideal.  Having an explicit priority for every kthread would probably
> be best.  Most kthreads should probably be at PZERO by default I think.

I'm not sure I agree here.
1) Maybe I missed it (so please point me to the right one) but I
didn't see a deep analysis of what messed up with the priorities there
2) I think this KPI can be dangerous and lead to problems. Priority is
something highly fragile.


Peace can only be achieved by understanding - A. Einstein

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