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Differential D17850

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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kib
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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

Diff Detail

Repository
rS FreeBSD src repository - subversion
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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 ↗(On Diff #50033)

Please add a comment explaining why sched_pin() is needed.

77 ↗(On Diff #50033)

Perhaps there another comment is needed, noting that tsc_is_invariant check prevent too long delays.

jhb updated this revision to Diff 50041.Nov 5 2018, 9:42 PM

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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head/
sys/
x86/
x86/
48 lines

Diff 50044

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head/sys/x86/x86/delay.c

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