HEADSUP: Realtime thread scheduling changed

John Baldwin jhb at freebsd.org
Fri Jan 14 18:01:02 UTC 2011

On Friday, January 14, 2011 12:22:18 pm Daniel Eischen wrote:
> On Fri, 14 Jan 2011, John Baldwin wrote:
> > This is just a heads up that I've committed some changes to how the scheduler
> > handles realtime thread priorities.  Please let me know of any issues you
> > encounter with nice, rtprio, or idprio.  Note that as a result of these
> > changes, rtprio threads will no longer share priorities with interactive
> > timeshare threads.  Instead, rtprio threads are now always more important than
> > non-rt threads.
> Cool - thanks for doing this!  Is this something that could
> be MFC'able to 8?

That's a harder question.  This changes the effective value of the P* priority
constants passed to *sleep().  That would be an ABI change for kernel modules.
We could either 1) decide that it is an ABI change worth making (probably
doubtful since it is mostly a new feature rather than a major bug fix) or
2) maybe MFC it but make the different priority ranges be subject to some
global kernel config option.  2) isn't super ideal since you have to really
make sure kernel modules are compiled with the same setting for that option
to avoid weird behavior.  I will MFC all the other changes I've made prior to
this in which case this change would be the only local patch someone would need
to have this.

John Baldwin

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