PPC: perf enhancement: Use larger heap page size on PPC.

Revisit of https://codereview.chromium.org/910333004.

Use 4MB heap page size over the default of 1MB.

This change provides an improvement of 1.86% on the composite octane
benchmark score on PPC. This is 0.56% more than if --min_semi_space_size=4
was used to specify a 4MB heap page size.

Additionally, two more tests required modification to account for
configurable heap page size.

R=svenpanne@chromium.org, hpayer@chromium.org, danno@chromium.org, mbrandy@us.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1221433022

Cr-Commit-Position: refs/heads/master@{#29775}

src/base/build_config.h

@@ -177,6 +177,11 @@
 
 // Number of bits to represent the page size for paged spaces. The value of 20
 // gives 1Mb bytes per page.
+#if V8_HOST_ARCH_PPC && V8_TARGET_ARCH_PPC && V8_OS_LINUX
+// Bump up for Power Linux due to larger (64K) page size.
+const int kPageSizeBits = 22;
+#else
 const int kPageSizeBits = 20;
+#endif
 
 #endif  // V8_BASE_BUILD_CONFIG_H_

src/heap/heap.cc

@@ -169,7 +169,7 @@ Heap::Heap()
 #endif
 
   // Ensure old_generation_size_ is a multiple of kPageSize.
-  DCHECK(MB >= Page::kPageSize);
+  DCHECK((max_old_generation_size_ & (Page::kPageSize - 1)) == 0);
 
   memset(roots_, 0, sizeof(roots_[0]) * kRootListLength);
   set_native_contexts_list(NULL);
@@ -5367,6 +5367,13 @@ bool Heap::ConfigureHeap(int max_semi_space_size, int max_old_space_size,
     max_executable_size_ = static_cast<intptr_t>(FLAG_max_executable_size) * MB;
   }
 
+  if (Page::kPageSize > MB) {
+    max_semi_space_size_ = ROUND_UP(max_semi_space_size_, Page::kPageSize);
+    max_old_generation_size_ =
+        ROUND_UP(max_old_generation_size_, Page::kPageSize);
+    max_executable_size_ = ROUND_UP(max_executable_size_, Page::kPageSize);
+  }
+
   if (FLAG_stress_compaction) {
     // This will cause more frequent GCs when stressing.
     max_semi_space_size_ = Page::kPageSize;
@@ -5392,12 +5399,6 @@ bool Heap::ConfigureHeap(int max_semi_space_size, int max_old_space_size,
     reserved_semispace_size_ = max_semi_space_size_;
   }
 
-  // The max executable size must be less than or equal to the max old
-  // generation size.
-  if (max_executable_size_ > max_old_generation_size_) {
-    max_executable_size_ = max_old_generation_size_;
-  }
-
   // The new space size must be a power of two to support single-bit testing
   // for containment.
   max_semi_space_size_ =
@@ -5416,7 +5417,8 @@ bool Heap::ConfigureHeap(int max_semi_space_size, int max_old_space_size,
                      max_semi_space_size_ / MB);
       }
     } else {
-      initial_semispace_size_ = initial_semispace_size;
+      initial_semispace_size_ =
+          ROUND_UP(initial_semispace_size, Page::kPageSize);
     }
   }
 
@@ -5441,7 +5443,7 @@ bool Heap::ConfigureHeap(int max_semi_space_size, int max_old_space_size,
                      max_semi_space_size_ / MB);
       }
     } else {
-      target_semispace_size_ = target_semispace_size;
+      target_semispace_size_ = ROUND_UP(target_semispace_size, Page::kPageSize);
     }
   }
 
@@ -5457,6 +5459,12 @@ bool Heap::ConfigureHeap(int max_semi_space_size, int max_old_space_size,
       Max(static_cast<intptr_t>(paged_space_count * Page::kPageSize),
           max_old_generation_size_);
 
+  // The max executable size must be less than or equal to the max old
+  // generation size.
+  if (max_executable_size_ > max_old_generation_size_) {
+    max_executable_size_ = max_old_generation_size_;
+  }
+
   if (FLAG_initial_old_space_size > 0) {
     initial_old_generation_size_ = FLAG_initial_old_space_size * MB;
   } else {

test/cctest/test-api.cc

@@ -17263,10 +17263,12 @@ class InitDefaultIsolateThread : public v8::base::Thread {
   void Run() {
     v8::Isolate::CreateParams create_params;
     create_params.array_buffer_allocator = CcTest::array_buffer_allocator();
+    const intptr_t pageSizeMult =
+        v8::internal::Page::kPageSize / v8::internal::MB;
     switch (testCase_) {
       case SetResourceConstraints: {
-        create_params.constraints.set_max_semi_space_size(1);
-        create_params.constraints.set_max_old_space_size(4);
+        create_params.constraints.set_max_semi_space_size(1 * pageSizeMult);
+        create_params.constraints.set_max_old_space_size(4 * pageSizeMult);
         break;
       }
       default:

test/cctest/test-strings.cc

@@ -1210,8 +1210,8 @@ TEST(SliceFromSlice) {
 UNINITIALIZED_TEST(OneByteArrayJoin) {
   v8::Isolate::CreateParams create_params;
   // Set heap limits.
-  create_params.constraints.set_max_semi_space_size(1);
-  create_params.constraints.set_max_old_space_size(6);
+  create_params.constraints.set_max_semi_space_size(1 * Page::kPageSize / MB);
+  create_params.constraints.set_max_old_space_size(6 * Page::kPageSize / MB);
   create_params.array_buffer_allocator = CcTest::array_buffer_allocator();
   v8::Isolate* isolate = v8::Isolate::New(create_params);
   isolate->Enter();