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[OpenMP] Improve performance of ticket lock (x86) (#143557)

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Ticket lock has a yield operation (shown below) which degrades
performance on larger server machines due to an unconditional pause
operation.

```
#define KMP_YIELD(cond)                                                        \
  {                                                                            \
    KMP_CPU_PAUSE();                                                           \
    if ((cond) && (KMP_TRY_YIELD))                                             \
      __kmp_yield();                                                           \
  }
```
This commit is contained in:
Jonathan Peyton 2025-07-21 08:26:35 -05:00 committed by GitHub
parent 8ba341eec3
commit c9fe19a99b
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1 changed files with 0 additions and 7 deletions
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7
openmp/runtime/src/kmp_lock.cpp
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@ -712,16 +712,9 @@ static int __kmp_test_ticket_lock_with_checks(kmp_ticket_lock_t *lck,
}
int __kmp_release_ticket_lock(kmp_ticket_lock_t *lck, kmp_int32 gtid) {
kmp_uint32 distance = std::atomic_load_explicit(&lck->lk.next_ticket,
std::memory_order_relaxed) -
std::atomic_load_explicit(&lck->lk.now_serving,
std::memory_order_relaxed);
std::atomic_fetch_add_explicit(&lck->lk.now_serving, 1U,
std::memory_order_release);
KMP_YIELD(distance >
(kmp_uint32)(__kmp_avail_proc ? __kmp_avail_proc : __kmp_xproc));
return KMP_LOCK_RELEASED;
}