Date: Mon, 18 May 2009 14:57:24 -0400 From: John Baldwin <jhb@freebsd.org> To: Attilio Rao <attilio@freebsd.org> Cc: Adam McDougall <mcdouga9@egr.msu.edu>, freebsd-current@freebsd.org, Artem Belevich <fbsdlist@src.cx>, Ben Kelly <ben@wanderview.com> Subject: Re: [patch] zfs livelock and thread priorities Message-ID: <200905181457.25238.jhb@freebsd.org> In-Reply-To: <3bbf2fe10905181038geaec26csffea4788a40feaca@mail.gmail.com> References: <08D7DC2A-68BE-47B6-8D5D-5DE6B48F87E5@wanderview.com> <200905181331.11174.jhb@freebsd.org> <3bbf2fe10905181038geaec26csffea4788a40feaca@mail.gmail.com>
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On Monday 18 May 2009 1:38:03 pm Attilio Rao wrote: > 2009/5/18 John Baldwin <jhb@freebsd.org>: > > On Monday 18 May 2009 1:12:59 pm Attilio Rao wrote: > >> 2009/5/18 John Baldwin <jhb@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). -- John Baldwinhelp
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