kc3-lang/angle/src/common/Spinlock.h

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• Hash : 9faf7059
  Author :
  Date : 2023-06-20T19:04:49
  

  Optimize angle::Spinlock performance
  
  This optimization is a preparation for future commits.
  
  Performance was tested by defining `ContextMutexType = angle::Spinlock`
  to use `SharedContextMutex<angle::Spinlock>` as `mSharedContextMutex`.
  
  Test result is average time for 1000'000 `glGetError()` calls on S906B
  with locked CPU frequencies:
  
      SharedContextMutex<angle::Spinlock>
          Before the optimization:        14.289 ms
          After the optimization:         12.941 ms (-9.4%)
  
  Performance when not using `angle::Spinlock` (current code):
  
      SingleContextMutex:                  9.115 ms  (-36.2%)
      SharedContextMutex<std::mutex>:     29.186 ms (+204.3%)
  
  Bug: angleproject:8226
  Change-Id: I447ff807cd6b72ff3fc115e73736fe63eb642785
  Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4632728
  Commit-Queue: Igor Nazarov <i.nazarov@samsung.com>
  Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
  

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• src/common/Spinlock.h

• //
  // Copyright 2021 The ANGLE Project Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  //
  // Spinlock.h:
  //   Spinlock is a lock that loops actively until it gets the resource.
  //   Only use it when the lock will be granted in reasonably short time.
  
  #ifndef COMMON_SPINLOCK_H_
  #define COMMON_SPINLOCK_H_
  
  #include "common/angleutils.h"
  
  #ifdef _MSC_VER
  #    include <intrin.h>  // for _mm_pause() and __yield()
  #endif
  
  #if defined(__ARM_ARCH_7__) || defined(__aarch64__)
  #    if defined(__GNUC__) || defined(__clang__)
  #        include <arm_acle.h>  // for __yield()
  #    endif
  #endif
  
  #if defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
  #    define ANGLE_SMT_PAUSE() _mm_pause()
  #elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
  #    define ANGLE_SMT_PAUSE() __asm__ __volatile__("pause;")
  #elif defined(_M_ARM) || defined(_M_ARM64) || defined(__ARM_ARCH_7__) || defined(__aarch64__)
  #    define ANGLE_SMT_PAUSE() __yield()
  #else
  #    define ANGLE_SMT_PAUSE() static_cast<void>(0)
  #endif
  
  namespace angle
  {
  
  class Spinlock
  {
    public:
      Spinlock() noexcept;
  
      bool try_lock() noexcept;
      void lock() noexcept;
      void unlock() noexcept;
  
    private:
      std::atomic_int mLock;
  };
  
  ANGLE_INLINE Spinlock::Spinlock() noexcept : mLock(0) {}
  
  ANGLE_INLINE bool Spinlock::try_lock() noexcept
  {
      // Relaxed check first to prevent unnecessary cache misses.
      return mLock.load(std::memory_order_relaxed) == 0 &&
             mLock.exchange(1, std::memory_order_acquire) == 0;
  }
  
  ANGLE_INLINE void Spinlock::lock() noexcept
  {
      while (mLock.exchange(1, std::memory_order_acquire) != 0)
      {
          // Relaxed wait to prevent unnecessary cache misses.
          while (mLock.load(std::memory_order_relaxed) != 0)
          {
              // Optimization for simultaneous multithreading.
              ANGLE_SMT_PAUSE();
          }
      }
  }
  
  ANGLE_INLINE void Spinlock::unlock() noexcept
  {
      mLock.store(0, std::memory_order_release);
  }
  
  }  // namespace angle
  
  #endif  // COMMON_SPINLOCK_H_
  

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