Date: Tue, 19 May 2009 08:31:48 -0400 From: John Baldwin <jhb@freebsd.org> To: Ben Kelly <ben@wanderview.com> Cc: Adam McDougall <mcdouga9@egr.msu.edu>, freebsd-current@freebsd.org, Artem Belevich <fbsdlist@src.cx> Subject: Re: [patch] zfs livelock and thread priorities Message-ID: <200905190831.48523.jhb@freebsd.org> In-Reply-To: <A0A6EFA4-1827-4BCF-8A45-C65298EC5A55@wanderview.com> References: <08D7DC2A-68BE-47B6-8D5D-5DE6B48F87E5@wanderview.com> <200905181129.51526.jhb@freebsd.org> <A0A6EFA4-1827-4BCF-8A45-C65298EC5A55@wanderview.com>
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On Monday 18 May 2009 10:16:46 pm Ben Kelly wrote: > On May 18, 2009, at 11:29 AM, John Baldwin wrote: > > 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. > > If this approach was taken would it make sense to use a flag to > indicate "use the specified priority" since 0 is a valid priority value? Well, 0 isn't truly valid (it's sort of reserved I guess), and we already use 0 for tsleep() to mean "don't change my priority". However, I would almost be inclined to just KASSERT() that the priority argument is not 0 and require each place that creates a kthread to explicitly set the new thread's priority. -- John Baldwin
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