add test for numeric -> string conversions

[folly.git] / folly / SmallLocks.h

diff --git a/folly/SmallLocks.h b/folly/SmallLocks.h
index 51abb97c738608bf346165117e51eb5989ccd874..01387aee724eae06da863f6f48f346db9be4cd9d 100644 (file)
--- a/folly/SmallLocks.h
+++ b/folly/SmallLocks.h
@@ -1,5 +1,5 @@
 /*
- * Copyright 2012 Facebook, Inc.
+ * Copyright 2013 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -34,6 +34,7 @@
  * @author Jordan DeLong <delong.j@fb.com>
  */
 
+#include <array>
 #include <cinttypes>
 #include <type_traits>
 #include <ctime>
@@ -48,6 +49,8 @@
 # error "SmallLocks.h is currently x64-only."
 #endif
 
+#include "folly/Portability.h"
+
 namespace folly {
 
 //////////////////////////////////////////////////////////////////////
@@ -172,7 +175,7 @@ struct PicoSpinLock {
                   sizeof(IntType) == 8,
                 "PicoSpinLock can't work on integers smaller than 2 bytes");
 
-public:
+ public:
   static const UIntType kLockBitMask_ = UIntType(1) << Bit;
   UIntType lock_;
 
@@ -275,6 +278,50 @@ public:
 
 //////////////////////////////////////////////////////////////////////
 
+/**
+ * Array of spinlocks where each one is padded to prevent false sharing.
+ * Useful for shard-based locking implementations in environments where
+ * contention is unlikely.
+ */
+
+// TODO: generate it from configure (`getconf LEVEL1_DCACHE_LINESIZE`)
+#define FOLLY_CACHE_LINE_SIZE 64
+
+template <class T, size_t N>
+struct SpinLockArray {
+  T& operator[](size_t i) {
+    return data_[i].lock;
+  }
+
+  const T& operator[](size_t i) const {
+    return data_[i].lock;
+  }
+
+  constexpr size_t size() const { return N; }
+
+ private:
+  struct PaddedSpinLock {
+    PaddedSpinLock() : lock() { }
+    T lock;
+    char padding[FOLLY_CACHE_LINE_SIZE - sizeof(T)];
+  };
+  static_assert(sizeof(PaddedSpinLock) == FOLLY_CACHE_LINE_SIZE,
+                "Invalid size of PaddedSpinLock");
+
+  // Check if T can theoretically cross a cache line.
+  // NOTE: It should be alignof(std::max_align_t), but max_align_t
+  // isn't supported by gcc 4.6.2.
+  static_assert(alignof(MaxAlign) > 0 &&
+                FOLLY_CACHE_LINE_SIZE % alignof(MaxAlign) == 0 &&
+                sizeof(T) <= alignof(MaxAlign),
+                "T can cross cache line boundaries");
+
+  char padding_[FOLLY_CACHE_LINE_SIZE];
+  std::array<PaddedSpinLock, N> data_;
+} __attribute__((aligned));
+
+//////////////////////////////////////////////////////////////////////
+
 typedef std::lock_guard<MicroSpinLock> MSLGuard;
 
 //////////////////////////////////////////////////////////////////////