Messages in this thread | | | Date | Wed, 7 Oct 2020 14:29:23 +0200 | From | Michal Hocko <> | Subject | Re: [RFC PATCH] kernel: allow to configure PREEMPT_NONE, PREEMPT_VOLUNTARY on kernel command line |
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On Wed 07-10-20 14:19:39, Peter Zijlstra wrote: > On Wed, Oct 07, 2020 at 02:04:01PM +0200, Michal Hocko wrote: > > From: Michal Hocko <mhocko@suse.com> > > > > Many people are still relying on pre built distribution kernels and so > > distributions have to provide mutliple kernel flavors to offer different > > preemption models. Most of them are providing PREEMPT_NONE for typical > > server deployments and PREEMPT_VOLUNTARY for desktop users. > > Is there actually a benefit to NONE? We were recently talking about > removing it.
I believe Mel can provide much better insight. We have been historically using PREEMPT_NONE for our enterprise customers mostly for nice throughput numbers. Many users are really targeting throughput much more than latencies. My understanding is that even though VOLUNTARY preemption model doesn't add too many preemption points on top of NONE it is still something that is observable (IIRC 2-3% on hackbench).
> The much more interesting (runtime) switch (IMO) would be between > VOLUNTARY and PREEMPT.
Absolutely and as said we are looking into that. This is meant to be a first baby step in that direction. Still very useful in our current situation when we want to provide both NONE and VOLUNTARY.
-- Michal Hocko SUSE Labs
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