git: libthread_xu - Improve contended mutex code

[Matthew Dillon]

commit f56151fa43e3b9a933b2c10ac2bbab0421823e12
Author: Matthew Dillon <dillon at apollo.backplane.com>
Date:   Sun Apr 22 19:29:58 2018 -0700

    libthread_xu - Improve contended mutex code
    
    * Retry a few times in a loop before using the umtx*() system
      calls to sleep.
    
      This significantly reduces IPI traffic and improves performance
      when a mutex is heavily contended.

Summary of changes:
 lib/libthread_xu/thread/thr_umtx.c | 48 +++++++++++++++++++++-----------------
 lib/libthread_xu/thread/thr_umtx.h | 25 +++++++++++++-------
 2 files changed, 43 insertions(+), 30 deletions(-)

http://gitweb.dragonflybsd.org/dragonfly.git/commitdiff/f56151fa43e3b9a933b2c10ac2bbab0421823e12


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