Messages in this thread | | | Date | Fri, 27 Nov 2015 10:17:02 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 3/4] sched: introduce synchronized idle injection |
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* Jacob Pan <jacob.jun.pan@linux.intel.com> wrote:
> On Wed, 18 Nov 2015 09:36:22 +0100 > Ingo Molnar <mingo@kernel.org> wrote: > > > > > > > This patch introduces a scheduler based idle injection method, it > > > works by blocking CFS runqueue synchronously and periodically. The > > > actions on all online CPUs are orchestrated by per CPU hrtimers. > > > > > > Two sysctl knobs are given to the userspace for selecting the > > > percentage of idle time as well as the forced idle duration for each > > > idle period injected. > > > > What's the purpose of these knobs? Just testing, or will some > > user-space daemon set them dynamically? > > > yes, it is to be used by userspace daemon such as thermal daemon. > Though there are interests from in kernel thermal governor but that is > another story.
Yeah, so let me make this very clear: for a kernel scheduling feature to be self-sufficient is not 'another story', but a must-have aspect for this feature to become upstream acceptable.
We don't add scheduler features that rely on pushing 'policy' to user-space. That's poor design with many disadvantages. This feature should offer a reasonable and automatic in-kernel default behavior with numbers that prove that it works.
Keeping an essential part of the feature in user-space earns a NAK from me.
Thanks,
Ingo
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