Add a delay_tsc() static function for when DELAY() uses the TSC.
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Authored by jhb on Nov 5 2018, 6:12 PM.

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rS340168: Add a delay_tsc() static function for when DELAY() uses the TSC.

Summary

This uses slightly simpler logic than the existing code by using the
full 64-bit counter and thus not having to worry about counter overflow.

Test Plan

passed make tinderbox (aside from unrelated breakage in arm.GENERIC-NODEBUG)
booted in i386 and amd64 VMs
original PR reporter booted combined patch on amd64 machine

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Build Status

Buildable 20645
Build 20061: arc lint + arc unit

Event Timeline

jhb created this revision.Nov 5 2018, 6:12 PM

Harbormaster completed remote builds in B20641: Diff 50033.Nov 5 2018, 6:12 PM

jhb added a parent revision: D17849: Add a KPI for the delay while spinning on a spin lock..Nov 5 2018, 6:14 PM

jhb added a child revision: D17851: Add a custom implementation of cpu_lock_delay() for x86..

kib added inline comments.Nov 5 2018, 9:19 PM

sys/x86/x86/delay.c
59–70	Please add a comment explaining why sched_pin() is needed.
81	Perhaps there another comment is needed, noting that tsc_is_invariant check prevent too long delays.

Add some comments.

Harbormaster completed remote builds in B20645: Diff 50041.Nov 5 2018, 9:42 PM

jhb marked 2 inline comments as done.Nov 5 2018, 9:44 PM

kib accepted this revision.Nov 5 2018, 9:59 PM

This revision is now accepted and ready to land.Nov 5 2018, 9:59 PM

Closed by commit rS340168: Add a delay_tsc() static function for when DELAY() uses the TSC. (authored by jhb). · Explain WhyNov 5 2018, 10:52 PM

This revision was automatically updated to reflect the committed changes.

Herald added a subscriber: imp. · View Herald TranscriptNov 5 2018, 10:52 PM

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sys/

x86/

delay.c

48 lines

Diff 50041

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Add a delay_tsc() static function for when DELAY() uses the TSC.ClosedPublicActions