Make arena use hugepage if possible

Summary:
arena doesn't use huge page by default. This change will make it happen
if possible. A new paramerter is added for Arena(). If it's set, Arena
will use huge page always. If huge page allocation fails, Arena
allocation will fallback to malloc().

Test Plan:
Change util/arena_test to support huge page allocation.
Run below tests:
1. normal regression test:
  make check
2. Check if huge page allocation works
  echo 50 > /proc/sys/vm/nr_hugepages
  make check

Reviewers: sdong

Reviewed By: sdong

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D28647

util/arena.cc

@@ -32,13 +32,20 @@ size_t OptimizeBlockSize(size_t block_size) {
   return block_size;
 }
 
-Arena::Arena(size_t block_size) : kBlockSize(OptimizeBlockSize(block_size)) {
+Arena::Arena(size_t block_size, size_t huge_page_size)
+    : kBlockSize(OptimizeBlockSize(block_size)) {
   assert(kBlockSize >= kMinBlockSize && kBlockSize <= kMaxBlockSize &&
          kBlockSize % kAlignUnit == 0);
   alloc_bytes_remaining_ = sizeof(inline_block_);
   blocks_memory_ += alloc_bytes_remaining_;
   aligned_alloc_ptr_ = inline_block_;
   unaligned_alloc_ptr_ = inline_block_ + alloc_bytes_remaining_;
+#ifdef MAP_HUGETLB
+  hugetlb_size_ = huge_page_size;
+  if (hugetlb_size_ && kBlockSize > hugetlb_size_) {
+    hugetlb_size_ = ((kBlockSize - 1U) / hugetlb_size_ + 1U) * hugetlb_size_;
+  }
+#endif
 }
 
 Arena::~Arena() {
@@ -62,20 +69,49 @@ char* Arena::AllocateFallback(size_t bytes, bool aligned) {
   }
 
   // We waste the remaining space in the current block.
-  auto block_head = AllocateNewBlock(kBlockSize);
+  size_t size;
-  alloc_bytes_remaining_ = kBlockSize - bytes;
+  char* block_head = nullptr;
+  if (hugetlb_size_) {
+    size = hugetlb_size_;
+    block_head = AllocateFromHugePage(size);
+  }
+  if (!block_head) {
+    size = kBlockSize;
+    block_head = AllocateNewBlock(size);
+  }
+  alloc_bytes_remaining_ = size - bytes;
 
   if (aligned) {
     aligned_alloc_ptr_ = block_head + bytes;
-    unaligned_alloc_ptr_ = block_head + kBlockSize;
+    unaligned_alloc_ptr_ = block_head + size;
     return block_head;
   } else {
     aligned_alloc_ptr_ = block_head;
-    unaligned_alloc_ptr_ = block_head + kBlockSize - bytes;
+    unaligned_alloc_ptr_ = block_head + size - bytes;
     return unaligned_alloc_ptr_;
   }
 }
 
+char* Arena::AllocateFromHugePage(size_t bytes) {
+#ifdef MAP_HUGETLB
+  if (hugetlb_size_ == 0) {
+    return nullptr;
+  }
+
+  void* addr = mmap(nullptr, bytes, (PROT_READ | PROT_WRITE),
+                    (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB), 0, 0);
+
+  if (addr == MAP_FAILED) {
+    return nullptr;
+  }
+  huge_blocks_.push_back(MmapInfo(addr, bytes));
+  blocks_memory_ += bytes;
+  return reinterpret_cast<char*>(addr);
+#else
+  return nullptr;
+#endif
+}
+
 char* Arena::AllocateAligned(size_t bytes, size_t huge_page_size,
                              Logger* logger) {
   assert((kAlignUnit & (kAlignUnit - 1)) ==
@@ -88,17 +124,14 @@ char* Arena::AllocateAligned(size_t bytes, size_t huge_page_size,
     size_t reserved_size =
         ((bytes - 1U) / huge_page_size + 1U) * huge_page_size;
     assert(reserved_size >= bytes);
-    void* addr = mmap(nullptr, reserved_size, (PROT_READ | PROT_WRITE),
-                      (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB), 0, 0);
 
-    if (addr == MAP_FAILED) {
+    char* addr = AllocateFromHugePage(reserved_size);
+    if (addr == nullptr) {
       Warn(logger, "AllocateAligned fail to allocate huge TLB pages: %s",
            strerror(errno));
       // fail back to malloc
     } else {
-      blocks_memory_ += reserved_size;
+      return addr;
-      huge_blocks_.push_back(MmapInfo(addr, reserved_size));
-      return reinterpret_cast<char*>(addr);
     }
   }
 #endif

util/arena.h

@@ -35,7 +35,10 @@ class Arena {
   static const size_t kMinBlockSize;
   static const size_t kMaxBlockSize;
 
-  explicit Arena(size_t block_size = kMinBlockSize);
+  // huge_page_size: if 0, don't use huge page TLB. If > 0 (should set to the
+  // supported hugepage size of the system), block allocation will try huge
+  // page TLB first. If allocation fails, will fall back to normal case.
+  explicit Arena(size_t block_size = kMinBlockSize, size_t huge_page_size = 0);
   ~Arena();
 
   char* Allocate(size_t bytes);
@@ -100,6 +103,8 @@ class Arena {
   // How many bytes left in currently active block?
   size_t alloc_bytes_remaining_ = 0;
 
+  size_t hugetlb_size_ = 0;
+  char* AllocateFromHugePage(size_t bytes);
   char* AllocateFallback(size_t bytes, bool aligned);
   char* AllocateNewBlock(size_t block_bytes);
 

util/arena_test.cc

@@ -13,17 +13,21 @@
 
 namespace rocksdb {
 
+namespace {
+const size_t kHugePageSize = 2 * 1024 * 1024;
+}  // namespace
 class ArenaTest {};
 
 TEST(ArenaTest, Empty) { Arena arena0; }
 
-TEST(ArenaTest, MemoryAllocatedBytes) {
+namespace {
+void MemoryAllocatedBytesTest(size_t huge_page_size) {
   const int N = 17;
   size_t req_sz;  // requested size
   size_t bsz = 8192;  // block size
   size_t expected_memory_allocated;
 
-  Arena arena(bsz);
+  Arena arena(bsz, huge_page_size);
 
   // requested size > quarter of a block:
   //   allocate requested size separately
@@ -44,8 +48,15 @@ TEST(ArenaTest, MemoryAllocatedBytes) {
   for (int i = 0; i < N; i++) {
     arena.Allocate(req_sz);
   }
+  if (huge_page_size) {
+    ASSERT_TRUE(arena.MemoryAllocatedBytes() ==
+                    expected_memory_allocated + bsz ||
+                arena.MemoryAllocatedBytes() ==
+                    expected_memory_allocated + huge_page_size);
+  } else {
     expected_memory_allocated += bsz;
     ASSERT_EQ(arena.MemoryAllocatedBytes(), expected_memory_allocated);
+  }
 
   // requested size > quarter of a block:
   //   allocate requested size separately
@@ -54,16 +65,23 @@ TEST(ArenaTest, MemoryAllocatedBytes) {
     arena.Allocate(req_sz);
   }
   expected_memory_allocated += req_sz * N;
+  if (huge_page_size) {
+    ASSERT_TRUE(arena.MemoryAllocatedBytes() ==
+                    expected_memory_allocated + bsz ||
+                arena.MemoryAllocatedBytes() ==
+                    expected_memory_allocated + huge_page_size);
+  } else {
     ASSERT_EQ(arena.MemoryAllocatedBytes(), expected_memory_allocated);
+  }
 }
 
 // Make sure we didn't count the allocate but not used memory space in
 // Arena::ApproximateMemoryUsage()
-TEST(ArenaTest, ApproximateMemoryUsageTest) {
+static void ApproximateMemoryUsageTest(size_t huge_page_size) {
   const size_t kBlockSize = 4096;
   const size_t kEntrySize = kBlockSize / 8;
   const size_t kZero = 0;
-  Arena arena(kBlockSize);
+  Arena arena(kBlockSize, huge_page_size);
   ASSERT_EQ(kZero, arena.ApproximateMemoryUsage());
 
   // allocate inline bytes
@@ -78,7 +96,12 @@ TEST(ArenaTest, ApproximateMemoryUsageTest) {
   // first allocation
   arena.AllocateAligned(kEntrySize);
   auto mem_usage = arena.MemoryAllocatedBytes();
+  if (huge_page_size) {
+    ASSERT_TRUE(mem_usage == kBlockSize + Arena::kInlineSize ||
+                mem_usage == huge_page_size + Arena::kInlineSize);
+  } else {
     ASSERT_EQ(mem_usage, kBlockSize + Arena::kInlineSize);
+  }
   auto usage = arena.ApproximateMemoryUsage();
   ASSERT_LT(usage, mem_usage);
   for (size_t i = 1; i < num_blocks; ++i) {
@@ -87,12 +110,17 @@ TEST(ArenaTest, ApproximateMemoryUsageTest) {
     ASSERT_EQ(arena.ApproximateMemoryUsage(), usage + kEntrySize);
     usage = arena.ApproximateMemoryUsage();
   }
+  if (huge_page_size) {
+    ASSERT_TRUE(usage > mem_usage ||
+                usage + huge_page_size - kBlockSize == mem_usage);
+  } else {
     ASSERT_GT(usage, mem_usage);
+  }
 }
 
-TEST(ArenaTest, Simple) {
+static void SimpleTest(size_t huge_page_size) {
   std::vector<std::pair<size_t, char*>> allocated;
-  Arena arena;
+  Arena arena(Arena::kMinBlockSize, huge_page_size);
   const int N = 100000;
   size_t bytes = 0;
   Random rnd(301);
@@ -136,7 +164,22 @@ TEST(ArenaTest, Simple) {
     }
   }
 }
+}  // namespace
+
+TEST(ArenaTest, MemoryAllocatedBytes) {
+  MemoryAllocatedBytesTest(0);
+  MemoryAllocatedBytesTest(kHugePageSize);
+}
 
+TEST(ArenaTest, ApproximateMemoryUsage) {
+  ApproximateMemoryUsageTest(0);
+  ApproximateMemoryUsageTest(kHugePageSize);
+}
+
+TEST(ArenaTest, Simple) {
+  SimpleTest(0);
+  SimpleTest(kHugePageSize);
+}
 }  // namespace rocksdb
 
 int main(int argc, char** argv) { return rocksdb::test::RunAllTests(); }