Support compaction for code space pages.

src/spaces.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1439 matching lines @@
 
   bool AdvanceSweeper(intptr_t bytes_to_sweep);
 
   bool IsSweepingComplete() {
     return !first_unswept_page_->is_valid();
   }
 
   Page* FirstPage() { return anchor_.next_page(); }
   Page* LastPage() { return anchor_.prev_page(); }
 
   bool IsFragmented(Page* p) {

[Erik Corry, 2011/09/06 14:10:31]

Perhaps this should always return true if the --always-compact flag is used.
Good for testing?

[Vyacheslav Egorov (Chromium), 2011/09/06 15:01:42]

Done.

     intptr_t sizes[4];
     free_list_.CountFreeListItems(p, sizes);
 
-    intptr_t ratio =
-        (sizes[0] * 5 + sizes[1]) * 100 / Page::kObjectAreaSize;
+    intptr_t ratio;
+    intptr_t ratio_threshold;
+    if (identity() == CODE_SPACE) {
+      ratio = (sizes[1] * 10 + sizes[2] * 2) * 100 / Page::kObjectAreaSize;
+      ratio_threshold = 10;
+    } else {
+      ratio = (sizes[0] * 5 + sizes[1]) * 100 / Page::kObjectAreaSize;
+      ratio_threshold = 15;
+    }
 
     if (FLAG_trace_fragmentation) {
-      PrintF("%p: %d (%.2f%%) %d (%.2f%%) %d (%.2f%%) %d (%.2f%%) %s\n",
+      PrintF("%p [%d]: %d (%.2f%%) %d (%.2f%%) %d (%.2f%%) %d (%.2f%%) %s\n",
              reinterpret_cast<void*>(p),
+             identity(),
              static_cast<int>(sizes[0]),
              static_cast<double>(sizes[0] * 100) / Page::kObjectAreaSize,
              static_cast<int>(sizes[1]),
              static_cast<double>(sizes[1] * 100) / Page::kObjectAreaSize,
              static_cast<int>(sizes[2]),
              static_cast<double>(sizes[2] * 100) / Page::kObjectAreaSize,
              static_cast<int>(sizes[3]),
              static_cast<double>(sizes[3] * 100) / Page::kObjectAreaSize,
-             (ratio > 15) ? "[fragmented]" : "");
+             (ratio > ratio_threshold) ? "[fragmented]" : "");
     }
 
-    return ratio > 15;
+    return ratio > ratio_threshold;
   }
 
   void EvictEvacuationCandidatesFromFreeLists();
 
  protected:
   // Maximum capacity of this space.
   intptr_t max_capacity_;
 
   // Accounting information for this space.
   AllocationStats accounting_stats_;
@@ skipping 1014 matching lines @@
   }
   // Must be small, since an iteration is used for lookup.
   static const int kMaxComments = 64;
 };
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_SPACES_H_