Re: [PATCH v2] sched: Warn on long periods of pending need_resched

Josh Don
2021-03-25T22:02:12Z

> 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.