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

["Jürgen Groß" <jgross@suse.com>]

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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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