Modify default alignment for UnboundedQueue to work correctly on ARM builds.

Summary: The original code provided an unsupported alignment for 32-bit ARM builds. This change makes use of hardware_destructive_interference_size, which represents exactly what the alignment field is used for.

Reviewed By: yfeldblum

Differential Revision: D6782366

fbshipit-source-id: b8e2cdf6a0bafdba96d40d729535646b1f6660df

folly/concurrency/UnboundedQueue.h

@@ -22,8 +22,10 @@
 
 #include <glog/logging.h>
 
+#include <folly/ConstexprMath.h>
 #include <folly/concurrency/CacheLocality.h>
 #include <folly/experimental/hazptr/hazptr.h>
+#include <folly/lang/Align.h>
 #include <folly/synchronization/SaturatingSemaphore.h>
 
 namespace folly {
@@ -197,7 +199,7 @@ template <
     bool SingleConsumer,
     bool MayBlock,
     size_t LgSegmentSize = 8,
-    size_t LgAlign = 7,
+    size_t LgAlign = constexpr_log2(hardware_destructive_interference_size),
     template <typename> class Atom = std::atomic>
 class UnboundedQueue {
   using Ticket = uint64_t;
@@ -724,7 +726,7 @@ template <
     typename T,
     bool MayBlock,
     size_t LgSegmentSize = 8,
-    size_t LgAlign = 7,
+    size_t LgAlign = constexpr_log2(hardware_destructive_interference_size),
     template <typename> class Atom = std::atomic>
 using USPSCQueue =
     UnboundedQueue<T, true, true, MayBlock, LgSegmentSize, LgAlign, Atom>;
@@ -733,7 +735,7 @@ template <
     typename T,
     bool MayBlock,
     size_t LgSegmentSize = 8,
-    size_t LgAlign = 7,
+    size_t LgAlign = constexpr_log2(hardware_destructive_interference_size),
     template <typename> class Atom = std::atomic>
 using UMPSCQueue =
     UnboundedQueue<T, false, true, MayBlock, LgSegmentSize, LgAlign, Atom>;
@@ -742,7 +744,7 @@ template <
     typename T,
     bool MayBlock,
     size_t LgSegmentSize = 8,
-    size_t LgAlign = 7,
+    size_t LgAlign = constexpr_log2(hardware_destructive_interference_size),
     template <typename> class Atom = std::atomic>
 using USPMCQueue =
     UnboundedQueue<T, true, false, MayBlock, LgSegmentSize, LgAlign, Atom>;
@@ -751,7 +753,7 @@ template <
     typename T,
     bool MayBlock,
     size_t LgSegmentSize = 8,
-    size_t LgAlign = 7,
+    size_t LgAlign = constexpr_log2(hardware_destructive_interference_size),
     template <typename> class Atom = std::atomic>
 using UMPMCQueue =
     UnboundedQueue<T, false, false, MayBlock, LgSegmentSize, LgAlign, Atom>;