[libcxx-commits] [PATCH] D126882: [libc++] Do not yield from __sp_mut::lock()

[Dimitry Andric via Phabricator via libcxx-commits]

dim added a comment.

To answer my own question partially, the original commit is Howard's: rG088e37c77aafaec5ead8fbe7ebf918265e6b86f2 <https://reviews.llvm.org/rG088e37c77aafaec5ead8fbe7ebf918265e6b86f2>:

> Despite my pathological distrust of spin locks, the number just don't lie.  I've put a small spin in __sp_mut::lock() on std::mutex::try_lock(), which is testing quite well.  In my experience, putting in a yield for every failed iteration is also a major performance booster.  This change makes one of the performance tests I was using (a highly contended one) run about 20 times faster.

But this was on macOS at the time, so ~2012...


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D126882/new/

https://reviews.llvm.org/D126882