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Differential D22746

Eliminate lock recursion from turnstiles.
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Authored by jeff on Dec 10 2019, 6:16 AM.
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jhb
kib
mav
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rS355782: schedlock 3/4
Summary

This avoids the one place we recursively lock turnstiles. In highly contended workloads the recursive locking actually imposes a performance penalty. We trade failed atomic cmpsets and multiple modifications to the lock cacheline for a few pointer comparisons.

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Buildable 28055
Build 26203: arc lint + arc unit

Event Timeline

jeff created this revision.Dec 10 2019, 6:16 AM
Harbormaster completed remote builds in B28055: Diff 65449.Dec 10 2019, 6:16 AM
jeff edited the summary of this revision. (Show Details)Dec 10 2019, 6:21 AM
jeff added reviewers: jhb, kib, mav.
jeff set the repository for this revision to rS FreeBSD src repository - subversion.
Herald added a subscriber: imp. · View Herald TranscriptDec 10 2019, 6:21 AM
kib accepted this revision.Dec 10 2019, 2:42 PM
This revision is now accepted and ready to land.Dec 10 2019, 2:42 PM
Closed by commit rS355782: schedlock 3/4 (authored by jeff). · Explain WhyDec 15 2019, 9:20 PM
This revision was automatically updated to reflect the committed changes.
jeff added a commit: rS355782: schedlock 3/4.

Revision Contents
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sys/
kern/
50 lines

Diff 65449

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sys/kern/subr_turnstile.c

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