Re: [PATCH 0/5] xen/sched: rtds: add per-cpupool admission control

[Jürgen Groß <jgross@xxxxxxxx>]

On 11.09.26 14:25, Furkan Çalışkan wrote:
> On 8/26/26 07:57, Furkan Caliskan wrote:
> > RTDS currently has no admission control: nothing stops the sum of
> > all admitted units' (budget/period) reservations in a cpupool from
> > exceeding what its pCPUs can actually provide. Once that happens,
> > the global-EDF deadline guarantees the scheduler is built around no
> > longer hold for any unit sharing that pool.
> >
> > This series adds admission control to prevent that, tracks and
> > report utilization, and makes the check toggleable per cpupool so
> > an operator can disable it if they intentionally want to overcommit.
> >
> > Patch 1 introduces the core mechanism: a running utilization total
> > per cpupool, a fixed-point representation of a unit's (budget/period),
> > and a capacity check enforced in rt_alloc_udata()/rt_free_udata() -
> > the lifecycle hooks that catch every new unit's default reservation.
> >
> > Patch 2 extends the same check to domctl, so growing an existing
> > reservation via xl sched-rtds is checked too.
> >
> > Patch 3 reports a cpupool's admitted utilization agains its capacity
> > via the 'r' debug key.
> >
> > Patch 4 makes admission control itself toggleable per cpupool
> > (enabled by default) via sysctl.
> >
> > Patch 5 wires that toggle through libxl and adds -s/-a to
> > xl sched-rtds, and documents it.
> >
> > Furkan Caliskan (5):
> >    xen/sched: rtds: add global-EDF utilization admission control
> >    xen/sched: rtds: enforce admission control in xl sched-rtds
> >    xen/sched: rtds: report utilization and cap via debug key
> >    xen/sched: rtds: make admission control cpupool-wide toggleable
> >    tools: expose admission control toggle via xl sched-rtds
> >
> >   docs/man/xl.1.pod.in                 |  20 +++
> >   tools/golang/xenlight/helpers.gen.go |  23 +++
> >   tools/golang/xenlight/types.gen.go   |   4 +
> >   tools/include/libxl.h                |   4 +
> >   tools/include/xenctrl.h              |   6 +
> >   tools/libs/ctrl/xc_rt.c              |  40 ++++++
> >   tools/libs/light/libxl_sched.c       |  46 ++++++
> >   tools/libs/light/libxl_types.idl     |   5 +
> >   tools/xl/xl_cmdtable.c               |   8 +-
> >   tools/xl/xl_sched.c                  | 103 +++++++++++++-
> >   xen/common/sched/rt.c                | 205 ++++++++++++++++++++++++++-
> >   xen/include/public/sysctl.h          |   5 +
> >   12 files changed, 463 insertions(+), 6 deletions(-)
> Hi Juergen,
>
> Can I get a review on this series please?
I was quite busy preparing for Xen summit. I'm planning to do the review on
the train to Munich. :-)


Juergen

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