Date: Wed, 23 Apr 2003 13:29:03 -0400 From: "Craig Reyenga" <creyenga@connectmail.carleton.ca> To: "John Baldwin" <jhb@freebsd.org> Cc: freebsd-current@freebsd.org Subject: Re: Renice idle process to -20 causes hang. Message-ID: <000b01c309bd$dbbd48b0$0200000a@fireball> References: <XFMail.20030423131324.jhb@FreeBSD.org>
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From: "John Baldwin" <jhb@freebsd.org> > > On 23-Apr-2003 Craig Reyenga wrote: > > While running a samba benchmark, I tried 'renice -n -20 10' (pid 10 is idle > > thread) to see what would happen. Turns out that this operation isn't > > illegal, and the system hung accordingly. The benchmark timed out soon > > after, and the console started displaying this message: > > > > swap_pager: indefinite wait buffer: device: ad0s1b, blkno: 776, size: 4096 > > > > over and over, although not rapidly. I'm not sure what to blame; perhaps > > setpriority() should return [EINVAL] or something. I can provide more info, > > upon request. > > Umm, yeah, setpriority should do an EINVAL, but that's not probably the > real bug. idlethreads are never on the run queues, they are truly idle > and only executed when there is nothing else to do. They don't have a > real priority other than "anything else is more important". What might have > happened is that setpiority() put the idle process on the run queue, which > is guaranteed to totally hose your system. > > Are you using SCHED_ULE or SCHED_4BSD? > > -- > > John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ > "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ > I am using SHED_ULE, and I have not yet tried this with SCHED_4BSD. I have already submitted a PR about this, perhaps a little prematurely. It's definitely a 'problem' though, because the system becomes unusable. I should also mention that any SSH sessions that were open already still work, until I try to run a new process, such as ls or something. -Craig
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