Revert "[scudo] Use getMonotonicTimeFast for tryLock." (#86590)

This reverts commit 36ca9a2902.

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.
This commit is contained in:
ChiaHungDuan
2024-03-27 11:30:08 -07:00
committed by GitHub
parent 2598aa67c8
commit f1ac559534

View File

@@ -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 {