From 346d1069c3031468cf5cb06299f018a873c9fb33 Mon Sep 17 00:00:00 2001
From: Daniel Black <daniel@linux.ibm.com>
Date: Mon, 25 Jun 2018 22:42:35 -0700
Subject: [PATCH] Align StatisticsImpl / StatisticsData (#4036)

Summary:
Pinned the alignment of StatisticsData to the cacheline size rather than just extending its size (which could go over two cache lines)if unaligned in allocation.

Avoid compile errors in the process as per individual commit messages.

strengthen static_assert to CACHELINE rather than the highest common multiple.
Closes https://github.com/facebook/rocksdb/pull/4036

Differential Revision: D8582844

Pulled By: yiwu-arbug

fbshipit-source-id: 363c37029f28e6093e06c60b987bca9aa204bc71
---
 Makefile                |  4 ++++
 monitoring/statistics.h | 17 ++++++++++++++---
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/Makefile b/Makefile
index 578031339..d9b5e11cd 100644
--- a/Makefile
+++ b/Makefile
@@ -102,6 +102,10 @@ OPT += -momit-leaf-frame-pointer
 endif
 endif
 
+ifeq (,$(shell $(CXX) -fsyntax-only -faligned-new -xc++ /dev/null 2>&1))
+CXXFLAGS += -faligned-new -DHAVE_ALIGNED_NEW
+endif
+
 ifeq (,$(shell $(CXX) -fsyntax-only -maltivec -xc /dev/null 2>&1))
 CXXFLAGS += -DHAS_ALTIVEC
 CFLAGS += -DHAS_ALTIVEC
diff --git a/monitoring/statistics.h b/monitoring/statistics.h
index 3bf20d4cf..a061d3ed2 100644
--- a/monitoring/statistics.h
+++ b/monitoring/statistics.h
@@ -22,6 +22,11 @@
 #define ROCKSDB_FIELD_UNUSED
 #endif  // __clang__
 
+#ifndef STRINGIFY
+#define STRINGIFY(x) #x
+#define TOSTRING(x) STRINGIFY(x)
+#endif
+
 namespace rocksdb {
 
 enum TickersInternal : uint32_t {
@@ -35,7 +40,7 @@ enum HistogramsInternal : uint32_t {
 };
 
 
-class StatisticsImpl : public Statistics {
+class ALIGN_AS(CACHE_LINE_SIZE) StatisticsImpl : public Statistics {
  public:
   StatisticsImpl(std::shared_ptr<Statistics> stats,
                  bool enable_internal_stats);
@@ -69,17 +74,23 @@ class StatisticsImpl : public Statistics {
   // cores can never share the same cache line.
   //
   // Alignment attributes expand to nothing depending on the platform
-  struct StatisticsData {
+  struct ALIGN_AS(CACHE_LINE_SIZE) StatisticsData {
     std::atomic_uint_fast64_t tickers_[INTERNAL_TICKER_ENUM_MAX] = {{0}};
     HistogramImpl histograms_[INTERNAL_HISTOGRAM_ENUM_MAX];
+#ifndef HAVE_ALIGNED_NEW
     char
         padding[(CACHE_LINE_SIZE -
                  (INTERNAL_TICKER_ENUM_MAX * sizeof(std::atomic_uint_fast64_t) +
                   INTERNAL_HISTOGRAM_ENUM_MAX * sizeof(HistogramImpl)) %
                      CACHE_LINE_SIZE)] ROCKSDB_FIELD_UNUSED;
+#endif
+    void *operator new(size_t s) { return port::cacheline_aligned_alloc(s); }
+    void *operator new[](size_t s) { return port::cacheline_aligned_alloc(s); }
+    void operator delete(void *p) { port::cacheline_aligned_free(p); }
+    void operator delete[](void *p) { port::cacheline_aligned_free(p); }
   };
 
-  static_assert(sizeof(StatisticsData) % 64 == 0, "Expected 64-byte aligned");
+  static_assert(sizeof(StatisticsData) % CACHE_LINE_SIZE == 0, "Expected " TOSTRING(CACHE_LINE_SIZE) "-byte aligned");
 
   CoreLocalArray<StatisticsData> per_core_stats_;