Startvation of realtime piority threads

[Sushanth Rai]

Thanks. I'll try to back port locally.

Sushanth

--- On Tue, 4/10/12, John Baldwin <jhb at freebsd.org> wrote:

> From: John Baldwin <jhb at freebsd.org>
> Subject: Re: Startvation of realtime piority threads
> To: "Sushanth Rai" <sushanth_rai at yahoo.com>
> Cc: freebsd-hackers at freebsd.org
> Date: Tuesday, April 10, 2012, 6:57 AM
> On Monday, April 09, 2012 4:32:24 pm
> Sushanth Rai wrote:
> > I'm using stock 7.2. The priorities as defined in
> priority.h are in this range:
> > 
> > /*
> >  * Priorities range from 0 to 255, but differences
> of less then 4 (RQ_PPQ)
> >  * are insignificant.  Ranges are as
> follows:
> >  *
> >  * Interrupt threads:       
>    0 - 63
> >  * Top half kernel threads: 
>    64 - 127
> >  * Realtime user threads:   
>    128 - 159
> >  * Time sharing user threads:   160
> - 223
> >  * Idle user threads:       
>    224 - 255
> >  *
> >  * XXX If/When the specific interrupt thread and
> top half thread ranges
> >  * disappear, a larger range can be used for user
> processes.
> >  */
> > 
> > The trouble is with vm_waitpfault(), which explicitly
> sleeps at PUSER.
> 
> Ah, yes, PUSER is the one Pxxx not in "top half kernel
> threads".  You can patch
> that locally, but you may have better lucking using 9.0 (or
> backporting my
> fixes in 9.0 back to 7 or 8).  They were too invasive
> to backport to FreeBSD
> 7/8, but you could still do it locally (I've used them at
> work on both 7 and 8).
> 
> -- 
> John Baldwin
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