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| author | ChiaHungDuan <chiahungduan@google.com> | 2024-03-27 11:30:08 -0700 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2024-03-27 11:30:08 -0700 |
| commit | f1ac559534788f8dd42191b60dfdf9cc56b39fd4 (patch) | |
| tree | 2bb12cba2ce75dc2c15eab4d43fbf90d1b996533 | |
| parent | 2598aa67c8fa733455af1b9738f257653ee6322b (diff) | |
| download | llvm-f1ac559534788f8dd42191b60dfdf9cc56b39fd4.zip llvm-f1ac559534788f8dd42191b60dfdf9cc56b39fd4.tar.gz llvm-f1ac559534788f8dd42191b60dfdf9cc56b39fd4.tar.bz2 | |
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.
| -rw-r--r-- | compiler-rt/lib/scudo/standalone/tsd.h | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/compiler-rt/lib/scudo/standalone/tsd.h b/compiler-rt/lib/scudo/standalone/tsd.h index b2108a0..72773f2 100644 --- a/compiler-rt/lib/scudo/standalone/tsd.h +++ b/compiler-rt/lib/scudo/standalone/tsd.h @@ -41,9 +41,9 @@ template <class Allocator> struct alignas(SCUDO_CACHE_LINE_SIZE) TSD { return true; } if (atomic_load_relaxed(&Precedence) == 0) - atomic_store_relaxed(&Precedence, - static_cast<uptr>(getMonotonicTimeFast() >> - FIRST_32_SECOND_64(16, 0))); + atomic_store_relaxed( + &Precedence, + static_cast<uptr>(getMonotonicTime() >> FIRST_32_SECOND_64(16, 0))); return false; } inline void lock() NO_THREAD_SAFETY_ANALYSIS { |