Differential D60434

libthr: Reorder pthread mutex to prevent false sharing
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Authored by aokblast on Wed, Oct 7, 7:25 AM.

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kib
markj

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rG99edcc3bd526: libthr: Reorder pthread mutex to prevent false sharing

Summary

On a 64 byte cache line CPU (amd64), m_owner is contended by all of
the shared processes. However, after finding one winner, mtx is
enqueued, which trigger a cache refresh from other processors. Reorder
mtx so that m_lock and m_qu will not be in the same cache line.

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rG FreeBSD src repository

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Buildable 77802
Build 74685: arc lint + arc unit

Event Timeline

aokblast created this revision.Wed, Oct 7, 7:25 AM

Herald added a subscriber: imp. · View Herald TranscriptWed, Oct 7, 7:25 AM

aokblast requested review of this revision.Wed, Oct 7, 7:25 AM

Harbormaster completed remote builds in B77802: Diff 188945.Wed, Oct 7, 7:25 AM

aokblast added reviewers: kib, markj.Wed, Oct 7, 7:26 AM

kib accepted this revision.Wed, Oct 7, 9:26 AM

This revision is now accepted and ready to land.Wed, Oct 7, 9:26 AM

markj accepted this revision.Wed, Oct 7, 2:34 PM

markj added inline comments.

lib/libthr/thread/thr_private.h
177	I'd amend this comment to explain that it's preferable to keep the linkage fields in a separate cache line.

aokblast added inline comments.Wed, Oct 7, 3:35 PM

lib/libthr/thread/thr_private.h
177	Thanks! I will also add some assertion test on LPI64 to indicate that these should not be sit in the same cache line.

Closed by commit rG99edcc3bd526: libthr: Reorder pthread mutex to prevent false sharing (authored by aokblast). · Explain WhyWed, Oct 7, 5:06 PM

This revision was automatically updated to reflect the committed changes.

aokblast added a commit: rG99edcc3bd526: libthr: Reorder pthread mutex to prevent false sharing.

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lib/

libthr/

thread/

2 lines

Diff 188945

lib/libthr/thread/thr_private.h

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