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Code Releases Wiki Activity

SpinLock: Overhaul false sharing avoidance

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This commit is contained in:
Pedro J. Estébanez
2024-11-13 10:45:43 +01:00
parent cb411fa960
commit a5caeeb664
1 changed files with 27 additions and 6 deletions
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29
core/os/spin_lock.h
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@@ -31,8 +31,15 @@
#ifndef SPIN_LOCK_H #ifndef SPIN_LOCK_H
#define SPIN_LOCK_H #define SPIN_LOCK_H
#include "core/os/thread.h"
#include "core/typedefs.h" #include "core/typedefs.h"
#ifdef THREADS_ENABLED
// Note the implementations below avoid false sharing by ensuring their
// sizes match the assumed cache line. We can't use align attributes
// because these objects may end up unaligned in semi-tightly packed arrays.
#ifdef _MSC_VER #ifdef _MSC_VER
#include <intrin.h> #include <intrin.h>
#endif #endif
@@ -42,7 +49,10 @@
#include <os/lock.h> #include <os/lock.h>
class SpinLock { class SpinLock {
union {
mutable os_unfair_lock _lock = OS_UNFAIR_LOCK_INIT; mutable os_unfair_lock _lock = OS_UNFAIR_LOCK_INIT;
char aligner[Thread::CACHE_LINE_BYTES];
};
public: public:
_ALWAYS_INLINE_ void lock() const { _ALWAYS_INLINE_ void lock() const {
@@ -54,9 +64,7 @@ public:
} }
}; };
#else #else // __APPLE__
#include "core/os/thread.h"
#include <atomic> #include <atomic>
@@ -84,8 +92,11 @@ _ALWAYS_INLINE_ static void _cpu_pause() {
static_assert(std::atomic_bool::is_always_lock_free); static_assert(std::atomic_bool::is_always_lock_free);
class alignas(Thread::CACHE_LINE_BYTES) SpinLock { class SpinLock {
union {
mutable std::atomic<bool> locked = ATOMIC_VAR_INIT(false); mutable std::atomic<bool> locked = ATOMIC_VAR_INIT(false);
char aligner[Thread::CACHE_LINE_BYTES];
};
public: public:
_ALWAYS_INLINE_ void lock() const { _ALWAYS_INLINE_ void lock() const {
@@ -107,4 +118,14 @@ public:
#endif // __APPLE__ #endif // __APPLE__
#else // THREADS_ENABLED
class SpinLock {
public:
void lock() const {}
void unlock() const {}
};
#endif // THREADS_ENABLED
#endif // SPIN_LOCK_H #endif // SPIN_LOCK_H