Add hardware_destructive_interference_size

[folly.git] / folly / concurrency / CacheLocality.h

diff --git a/folly/concurrency/CacheLocality.h b/folly/concurrency/CacheLocality.h
index 7751b7dc91b624a3d3137694990ebea271f88ee0..420f5334b5ac108e37695e5943b17b115b83ed03 100644 (file)
--- a/folly/concurrency/CacheLocality.h
+++ b/folly/concurrency/CacheLocality.h
@@ -116,22 +116,9 @@ struct CacheLocality {
   /// CacheLocality structure with the specified number of cpus and a
   /// single cache level that associates one cpu per cache.
   static CacheLocality uniform(size_t numCpus);
-
-  enum {
-    /// Memory locations on the same cache line are subject to false
-    /// sharing, which is very bad for performance.  Microbenchmarks
-    /// indicate that pairs of cache lines also see interference under
-    /// heavy use of atomic operations (observed for atomic increment on
-    /// Sandy Bridge).  See FOLLY_ALIGN_TO_AVOID_FALSE_SHARING
-    kFalseSharingRange = 128
-  };
-
-  static_assert(
-      kFalseSharingRange == 128,
-      "FOLLY_ALIGN_TO_AVOID_FALSE_SHARING should track kFalseSharingRange");
 };
 
-// TODO replace __attribute__ with alignas and 128 with kFalseSharingRange
+// TODO replace with alignas(hardware_destructive_interference_size)
 
 /// An attribute that will cause a variable or field to be aligned so that
 /// it doesn't have false sharing with anything at a smaller memory address.
@@ -451,14 +438,11 @@ class CoreAllocator {
     void* allocate(size_t size) {
       auto cl = sizeClass(size);
       if (cl == 4) {
-        static_assert(
-            CacheLocality::kFalseSharingRange == 128,
-            "kFalseSharingRange changed");
         // Align to a cacheline
-        size = size + (CacheLocality::kFalseSharingRange - 1);
-        size &= ~size_t(CacheLocality::kFalseSharingRange - 1);
-        void* mem =
-            detail::aligned_malloc(size, CacheLocality::kFalseSharingRange);
+        size = size + (hardware_destructive_interference_size - 1);
+        size &= ~size_t(hardware_destructive_interference_size - 1);
+        void* mem = detail::aligned_malloc(
+            size, hardware_destructive_interference_size);
         if (!mem) {
           std::__throw_bad_alloc();
         }