[patch] zfs livelock and thread priorities
jhb at freebsd.org
Mon May 18 19:06:02 UTC 2009
On Monday 18 May 2009 1:38:03 pm Attilio Rao wrote:
> 2009/5/18 John Baldwin <jhb at freebsd.org>:
> > On Monday 18 May 2009 1:12:59 pm Attilio Rao wrote:
> >> 2009/5/18 John Baldwin <jhb at freebsd.org>:
> >> > On Saturday 16 May 2009 12:40:44 pm Ben Kelly wrote:
> >> 2) I think this KPI can be dangerous and lead to problems. Priority is
> >> something highly fragile.
> > All the more reason to make developers _think_ about the priority of each
> > kthread they create. Right now all these threads start out with a priority
> > of PVM since that is what thread0 runs at. Does that sound right to you? Do
> > you think many folks realize that? It sounds very bogus to me. I think
> > forcing people to pick a sensible priority for each thread is far better than
> > the complete lack of thought that often happens now.
> At least, we could leave the default version not accepting any
> priority for threads which are not interested on that and trying to
> move people to the new KPI _only and if only_ they need real boosts or
> lay down.
I would rather force people to think. We've had problems in the past with
folks not thinking clearly enough (e.g. just using a constant to tsleep()
instead of figuring out a real timeout value to use).
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