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Enhance spin_adaptive() to yield after several iterations.

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This avoids worst case behavior if e.g. another thread is preempted
while owning the resource the spinning thread is waiting for.
This commit is contained in:
Jason Evans
2017-02-08 10:30:44 -08:00
parent 5f11830754
commit de8a68e853
3 changed files with 28 additions and 6 deletions
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17
include/jemalloc/internal/spin_inlines.h
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@@ -8,14 +8,19 @@ void spin_adaptive(spin_t *spin);
#if (defined(JEMALLOC_ENABLE_INLINE) || defined(JEMALLOC_SPIN_C_))
JEMALLOC_INLINE void
spin_adaptive(spin_t *spin) {
volatile uint64_t i;
volatile uint32_t i;
for (i = 0; i < (KQU(1) << spin->iteration); i++) {
CPU_SPINWAIT;
}
if (spin->iteration < 63) {
if (spin->iteration < 5) {
for (i = 0; i < (1U << spin->iteration); i++) {
CPU_SPINWAIT;
}
spin->iteration++;
} else {
#ifdef _WIN32
SwitchToThread();
#else
sched_yield();
#endif
}
}