Re: Noticable Delays Since Beta 3 (possible cause)

On Friday 08 October 2004 10:56 pm, Sam Lawrance wrote:
> I think I've found the cause of the delays.
>
> The problem was consistently reproducible with getty processes which are
> swapped out (ie 'ps' shows RSS=0 and state=IWs+).
>
> Since the problem was identifiable when starting to type at a vty, I
> traced the problem back through:
>
> ttyinput() : tty.c
> ttwakeup() : tty.c
> wakeup() : kern_synch.c
> sleepq_broadcast() : subr_sleepq.c
> sleepq_resume_thread() : subr_sleepq.c
> setrunnable() : kern_synch.c
>
> Notice in setrunnable() how wakeup(&proc0) is wrapped by #ifndef SMP?
> This means that scheduler() : vm/vm_glue.c, which tsleeps on proc0, is
> not awoken to traverse the process list and swap the process in.
>
> scheduler() tsleeps for a maximum of maxslp * hz / 2. maxslp on all
> archs appears to be 20, so the actual wakeup intended by ttwakeup() may
> not occur for up to 10 seconds.

I think I agree, FWIW.

Marc.

-- 
Marc Ramirez
Blue Circle Software Corporation
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