Implement a hash based look-up to speed up containing address check in large

object space. Before, it was a link-list based look-up, and make this function
a little bit 'hot' from profile point.

BUG=v8:853
TEST=

Review URL: https://chromiumcodereview.appspot.com/9634005
Patch from Zhongping Wang <kewpie.w.zp@gmail.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11084 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/frames.cc

@@ -1302,7 +1302,7 @@ Code* InnerPointerToCodeCache::GcSafeFindCodeForInnerPointer(
     Address inner_pointer) {
   Heap* heap = isolate_->heap();
   // Check if the inner pointer points into a large object chunk.
-  LargePage* large_page = heap->lo_space()->FindPageContainingPc(inner_pointer);
+  LargePage* large_page = heap->lo_space()->FindPage(inner_pointer);
   if (large_page != NULL) {
     return GcSafeCastToCode(large_page->GetObject(), inner_pointer);
   }

src/spaces.cc

@@ -2525,6 +2525,10 @@ HeapObject* LargeObjectIterator::Next() {
 
 // -----------------------------------------------------------------------------
 // LargeObjectSpace
+static bool ComparePointers(void* key1, void* key2) {
+    return key1 == key2;
+}
+
 
 LargeObjectSpace::LargeObjectSpace(Heap* heap,
                                    intptr_t max_capacity,
@@ -2534,7 +2538,8 @@ LargeObjectSpace::LargeObjectSpace(Heap* heap,
       first_page_(NULL),
       size_(0),
       page_count_(0),
-      objects_size_(0) {}
+      objects_size_(0),
+      chunk_map_(ComparePointers, 1024) {}
 
 
 bool LargeObjectSpace::SetUp() {
@@ -2542,6 +2547,7 @@ bool LargeObjectSpace::SetUp() {
   size_ = 0;
   page_count_ = 0;
   objects_size_ = 0;
+  chunk_map_.Clear();
   return true;
 }
 
@@ -2585,6 +2591,17 @@ MaybeObject* LargeObjectSpace::AllocateRaw(int object_size,
   page->set_next_page(first_page_);
   first_page_ = page;
 
+  // Register all MemoryChunk::kAlignment-aligned chunks covered by
+  // this large page in the chunk map.
+  uintptr_t base = reinterpret_cast<uintptr_t>(page)/MemoryChunk::kAlignment;
+  uintptr_t limit = base + (page->size()-1)/MemoryChunk::kAlignment;
+  for (uintptr_t key = base; key <= limit; key++) {
+    HashMap::Entry* entry = chunk_map_.Lookup(reinterpret_cast<void*>(key),
+                                              key, true);
+    ASSERT(entry != NULL);
+    entry->value = page;
+  }
+
   HeapObject* object = page->GetObject();
 
 #ifdef DEBUG
@@ -2601,27 +2618,24 @@ MaybeObject* LargeObjectSpace::AllocateRaw(int object_size,
 
 // GC support
 MaybeObject* LargeObjectSpace::FindObject(Address a) {
-  for (LargePage* page = first_page_;
-       page != NULL;
-       page = page->next_page()) {
-    Address page_address = page->address();
-    if (page_address <= a && a < page_address + page->size()) {
+  LargePage* page = FindPage(a);
+  if (page != NULL) {
     return page->GetObject();
   }
-  }
   return Failure::Exception();
 }
 
 
-LargePage* LargeObjectSpace::FindPageContainingPc(Address pc) {
-  // TODO(853): Change this implementation to only find executable
-  // chunks and use some kind of hash-based approach to speed it up.
-  for (LargePage* chunk = first_page_;
-       chunk != NULL;
-       chunk = chunk->next_page()) {
-    Address chunk_address = chunk->address();
-    if (chunk_address <= pc && pc < chunk_address + chunk->size()) {
-      return chunk;
+LargePage* LargeObjectSpace::FindPage(Address a) {
+  uintptr_t key = reinterpret_cast<uintptr_t>(a) / MemoryChunk::kAlignment;
+  HashMap::Entry* e = chunk_map_.Lookup(reinterpret_cast<void*>(key),
+                                        key, false);
+  if (e != NULL) {
+    ASSERT(e->value != NULL);
+    LargePage* page = reinterpret_cast<LargePage*>(e->value);
+    ASSERT(page->is_valid());
+    if (page->Contains(a)) {
+      return page;
     }
   }
   return NULL;
@@ -2659,6 +2673,16 @@ void LargeObjectSpace::FreeUnmarkedObjects() {
       objects_size_ -= object->Size();
       page_count_--;
 
+      // Remove entries belonging to this page.
+      // Use variable alignment to help pass length check (<= 80 characters)
+      // of single line in tools/presubmit.py.
+      const intptr_t alignment = MemoryChunk::kAlignment;
+      uintptr_t base = reinterpret_cast<uintptr_t>(page)/alignment;
+      uintptr_t limit = base + (page->size()-1)/alignment;
+      for (uintptr_t key = base; key <= limit; key++) {
+        chunk_map_.Remove(reinterpret_cast<void*>(key), key);
+      }
+
       if (is_pointer_object) {
         heap()->QueueMemoryChunkForFree(page);
       } else {

src/spaces.h

@@ -29,6 +29,7 @@
 #define V8_SPACES_H_
 
 #include "allocation.h"
+#include "hashmap.h"
 #include "list.h"
 #include "log.h"
 
@@ -2499,9 +2500,9 @@ class LargeObjectSpace : public Space {
   // space, may be slow.
   MaybeObject* FindObject(Address a);
 
-  // Finds a large object page containing the given pc, returns NULL
+  // Finds a large object page containing the given address, returns NULL
   // if such a page doesn't exist.
-  LargePage* FindPageContainingPc(Address pc);
+  LargePage* FindPage(Address a);
 
   // Frees unmarked objects.
   void FreeUnmarkedObjects();
@@ -2536,6 +2537,8 @@ class LargeObjectSpace : public Space {
   intptr_t size_;  // allocated bytes
   int page_count_;  // number of chunks
   intptr_t objects_size_;  // size of objects
+  // Map MemoryChunk::kAlignment-aligned chunks to large pages covering them
+  HashMap chunk_map_;
 
   friend class LargeObjectIterator;