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Re: [PATCH] Add 3.0-rc7-rt0 patch set



On Fri, 2011-07-22 at 11:42 +0200, Uwe Kleine-König wrote:
> Hello,
> 
> On Thu, Jul 21, 2011 at 11:32:52PM +0200, Ben Hutchings wrote:
> > On Thu, 2011-07-21 at 16:25 +0200, Uwe Kleine-König wrote:
> > >  # initramfs-generators
> > >  initramfs-fallback: linux-initramfs-tool
> > >  initramfs-tools: initramfs-tools (>= 0.99)
> > > diff --git a/config/featureset-rt/config b/config/featureset-rt/config
> > > new file mode 100644
> > > index 0000000..8136f16
> > > --- /dev/null
> > > +++ b/config/featureset-rt/config
> > > @@ -0,0 +1,5 @@
> > > +# CONFIG_PREEMPT_VOLUNTARY is not set
> > > +CONFIG_PREEMPT_RT_FULL=y
> > > +CONFIG_SCHED_TRACER=y
> > > +CONFIG_MISSED_TIMER_OFFSETS_HIST=y
> > > +CONFIG_WAKEUP_LATENCY_HIST=y
> > 
> > I notice that you leave Xen (and other pvops) support enabled.  I don't
> > think this makes sense, as virtualisation will add back the latency and
> > jitter that RT is trying to avoid.
> hmm, it might not make much sense to run Xen on top of an rt kernel,
> that's right. I'm not sure that disabling Xen (and others) is needed
> though. There is no exact definition of rt in general, it always depends
> on your use-case and then you have to verify/test if the machine you
> want to use is capable to fulfill your requirements. So IMHO it's OK to
> say: my machine is able to serve my rt requirements as long as it
> doesn't run (as) a Xen guest. Don't do it then. Or only do it when
> you're not recording audio.
> 
> I'm sure there are many things more that increase the maximal latency, I
> don't want (and cannot) go through all of them and choose if they are
> still OK or crossed the border.

True.

> I could still be conviced to disable these, but I don't find how to get
> rid of the "This kernel also runs on a Xen hypervisor.  It supports both
> privileged (dom0) and unprivileged (domU) operation." in the
> description. Hints welcome.

I think you would need to add a 'amd64_description' section in
debian/config/amd64/rt/defines, overriding the one in
debian/config/amd64/defines.  Not sure.

> > > diff --git a/config/featureset-rt/defines b/config/featureset-rt/defines
> > > new file mode 100644
> > > index 0000000..caf2baf
> > > --- /dev/null
> > > +++ b/config/featureset-rt/defines
> > > @@ -0,0 +1,7 @@
> > > +[abi]
> > > +ignore-changes: *
> > > +
> > > +[description]
> > > +part-long-rt: This kernel includes the PREEMPT_RT patch set
> > 
> > This should be a whole sentence, ending in a full stop (period).
> I guess just adding a period is good enough?

Yes.

Ben.

-- 
Ben Hutchings
Absolutum obsoletum. (If it works, it's out of date.) - Stafford Beer

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