On Wed, Mar 24, 2021 at 01:39:16PM +0000, Mel Gorman wrote:
I'm not going to NAK because I do not have hard data that shows they must
exist. However, I won't ACK either because I bet a lot of tasty beverages
the next time we meet that the following parameters will generate reports
if removed.

kernel.sched_latency_ns
kernel.sched_migration_cost_ns
kernel.sched_min_granularity_ns
kernel.sched_wakeup_granularity_ns

I know they are altered by tuned for different profiles and some people do
go the effort to create custom profiles for specific applications. They
also show up in "Official Benchmarking" such as SPEC CPU 2017 and
some vendors put a *lot* of effort into SPEC CPU results for bragging
rights. They show up in technical books and best practice guids for
applications.  Finally they show up in Google when searching for "tuning
sched_foo". I'm not saying that any of these are even accurate or a good
idea, just that they show up near the top of the results and they are
sufficiently popular that they might as well be an ABI.

+1, these seem like sufficiently well-known scheduler tunables, and
not really SCHED_DEBUG.