[all-commits] [llvm/llvm-project] f1ac55: Revert "[scudo] Use getMonotonicTimeFast for tryLo...

[ChiaHungDuan via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f1ac559534788f8dd42191b60dfdf9cc56b39fd4
      https://github.com/llvm/llvm-project/commit/f1ac559534788f8dd42191b60dfdf9cc56b39fd4
  Author: ChiaHungDuan <chiahungduan at google.com>
  Date:   2024-03-27 (Wed, 27 Mar 2024)

  Changed paths:
    M compiler-rt/lib/scudo/standalone/tsd.h

  Log Message:
  -----------
  Revert "[scudo] Use getMonotonicTimeFast for tryLock." (#86590)

This reverts commit 36ca9a29025a2f678096e9545fa2ec44e8432592.

We were using the `time` as the seed while choosing a new TSD. To make
the access of TSDs evenly distributed, we require a higher precision in
`time`. Otherwise, many threads may result in having the same random
access pattern on TSDs because they share the same `time` in certain
period. On Linux, CLOCK_MONOTONIC_COARSE usually adopts 4 ms precision.
This is way higher than the average accessing time of TSD (which is
usually less than 1 us). As a result, when multiple threads try to
select a new TSD in a 4 ms interval, they share the same `time` seed and
end up choosing and congesting on the same TSD.



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