Changes to improve the performance of reading a snapshot.

runtime/vm/pages.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/pages.h"
 
 #include "platform/assert.h"
 #include "vm/compiler_stats.h"
 #include "vm/gc_marker.h"
 #include "vm/gc_sweeper.h"
@@ skipping 207 matching lines @@
   }
 }
 
 
 uword PageSpace::TryAllocate(intptr_t size,
                              HeapPage::PageType type,
                              GrowthPolicy growth_policy) {
   ASSERT(size >= kObjectAlignment);
   ASSERT(Utils::IsAligned(size, kObjectAlignment));
   uword result = 0;
-  SpaceUsage after_allocation = usage_;
-  after_allocation.used_in_words += size >> kWordSizeLog2;
+  intptr_t after_capacity_in_words = usage_.capacity_in_words;
   if (size < kAllocatablePageSize) {
     const bool is_protected = (type == HeapPage::kExecutable)
         && FLAG_write_protect_code;
     result = freelist_[type].TryAllocate(size, is_protected);
     if (result == 0) {
       // Can we grow by one page?
-      after_allocation.capacity_in_words += kPageSizeInWords;
-      if ((!page_space_controller_.NeedsGarbageCollection(after_allocation) ||
-           growth_policy == kForceGrowth) &&
+      after_capacity_in_words += kPageSizeInWords;
+      const bool needs_gc = page_space_controller_.NeedsGarbageCollection(
+          after_capacity_in_words);
+      if ((!needs_gc || growth_policy == kForceGrowth) &&
           CanIncreaseCapacityInWords(kPageSizeInWords)) {
         HeapPage* page = AllocatePage(type);
         ASSERT(page != NULL);
         // Start of the newly allocated page is the allocated object.
         result = page->object_start();
         // Enqueue the remainder in the free list.
         uword free_start = result + size;
         intptr_t free_size = page->object_end() - free_start;
         if (free_size > 0) {
           freelist_[type].Free(free_start, free_size);
         }
       }
     }
   } else {
     // Large page allocation.
     intptr_t page_size_in_words = LargePageSizeInWordsFor(size);
     if ((page_size_in_words << kWordSizeLog2) < size) {
       // On overflow we fail to allocate.
       return 0;
     }
-    after_allocation.capacity_in_words += page_size_in_words;
-    if ((!page_space_controller_.NeedsGarbageCollection(after_allocation) ||
-         growth_policy == kForceGrowth) &&
+    after_capacity_in_words += page_size_in_words;
+    const bool needs_gc = page_space_controller_.NeedsGarbageCollection(
+          after_capacity_in_words);
+    if ((!needs_gc || growth_policy == kForceGrowth) &&
         CanIncreaseCapacityInWords(page_size_in_words)) {
       HeapPage* page = AllocateLargePage(size, type);
       if (page != NULL) {
         result = page->object_start();
       }
     }
   }
   if (result != 0) {
-    usage_ = after_allocation;
+    usage_.used_in_words += (size >> kWordSizeLog2);
+    usage_.capacity_in_words = after_capacity_in_words;
     if (FLAG_compiler_stats && (type == HeapPage::kExecutable)) {
       CompilerStats::code_allocated += size;
     }
   }
   ASSERT((result & kObjectAlignmentMask) == kOldObjectAlignmentOffset);
   return result;
 }
 
 
 void PageSpace::AllocateExternal(intptr_t size) {
@@ skipping 297 matching lines @@
       desired_utilization_((100.0 - heap_growth_ratio) / 100.0),
       heap_growth_max_(heap_growth_max),
       garbage_collection_time_ratio_(garbage_collection_time_ratio),
       last_code_collection_in_us_(OS::GetCurrentTimeMicros()) {
 }
 
 
 PageSpaceController::~PageSpaceController() {}
 
 
-bool PageSpaceController::NeedsGarbageCollection(SpaceUsage after) const {
+bool PageSpaceController::NeedsGarbageCollection(
+    intptr_t after_capacity_in_words) const {
   if (!is_enabled_) {
     return false;
   }
   if (heap_growth_ratio_ == 100) {
     return false;
   }
   intptr_t capacity_increase_in_words =
-    after.capacity_in_words - last_usage_.capacity_in_words;
+    after_capacity_in_words - last_usage_.capacity_in_words;
   ASSERT(capacity_increase_in_words >= 0);
   capacity_increase_in_words =
       Utils::RoundUp(capacity_increase_in_words, PageSpace::kPageSizeInWords);
   intptr_t capacity_increase_in_pages =
       capacity_increase_in_words / PageSpace::kPageSizeInWords;
   double multiplier = 1.0;
   // To avoid waste, the first GC should be triggered before too long. After
   // kInitialTimeoutSeconds, gradually lower the capacity limit.
   static const double kInitialTimeoutSeconds = 1.00;
   if (history_.IsEmpty()) {
@@ skipping 74 matching lines @@
     return 0;
   } else {
     ASSERT(total_time >= gc_time);
     int result= static_cast<int>((static_cast<double>(gc_time) /
                              static_cast<double>(total_time)) * 100);
     return result;
   }
 }
 
 }  // namespace dart