Handle multiple clock ticks in sched_clock()
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Authored by jeff on Dec 1 2019, 8:42 PM.

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Reviewers

mav
kib
jhb
markj
mjg

Commits

rS355512: Handle multiple clock interrupts simultaneously in sched_clock().

Summary

This was one optimization from https://github.com/freebsd/freebsd/compare/master...jwroberson:schedlock

It is relatively straightforward in ULE to handle a long set of idle ticks without looping. I did not attempt to do so for 4bsd. This also gives an early return for idlethread because it does not need interactivity or priority adjustments. It does run the percent cpu calculator.

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Repository

rS FreeBSD src repository - subversion

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Event Timeline

jeff created this revision.Dec 1 2019, 8:42 PM

Harbormaster completed remote builds in B27875: Diff 65105.Dec 1 2019, 8:42 PM

jeff edited the summary of this revision. (Show Details)Dec 1 2019, 8:44 PM

jeff added reviewers: mav, kib, jhb, markj, mjg.

jeff set the repository for this revision to rS FreeBSD src repository - subversion.

Herald added a subscriber: imp. · View Herald TranscriptDec 1 2019, 8:44 PM

kib accepted this revision.Dec 1 2019, 9:07 PM

This revision is now accepted and ready to land.Dec 1 2019, 9:07 PM

mav accepted this revision.Dec 1 2019, 10:42 PM

Looks same to me. The only macro difference is dropping the idle thread check. Is that intended? Is so, is it safe?

sys/kern/sched_ule.c
2468 ↗	(On Diff #65105)	Why did you drop the idle thread check,?

markj accepted this revision.Dec 2 2019, 4:49 PM

markj added inline comments.

sys/kern/sched_ule.c
2445 ↗	(On Diff #65105)	This comment is slightly wrong, we don't update the index once per tick.
2468 ↗	(On Diff #65105)	It is moved earlier. The change is a no-op since PRI_BASE(td->td_pri_class) != PRI_TIMESHARE for an idle thread.