| Date | Wed, 8 Nov 2023 10:15:52 -0500 | From | Steven Rostedt <> | Subject | Re: [RFC PATCH 00/86] Make the kernel preemptible |
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On Wed, 8 Nov 2023 09:43:10 +0000 David Laight <David.Laight@ACULAB.COM> wrote:
> > Policies: > > > > A - preemption=none: run to completion > > B - preemption=voluntary: run to completion, unless a task of higher > > sched-class awaits > > C - preemption=full: optimized for low-latency. Preempt whenever a higher > > priority task awaits. > > If you remove cond_resched() then won't both B and C require an extra IPI. > That is probably OK for RT tasks but could get expensive for > normal tasks that aren't bound to a specific cpu.
What IPI is extra?
> > I suspect C could also lead to tasks being pre-empted just before > they sleep (eg after waking another task). > There might already be mitigation for that, I'm not sure if > a voluntary sleep can be done in a non-pre-emptible section.
No, voluntary sleep can not be done in a preemptible section.
-- Steve
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