From e3774cf23f5033c34021122995ddcfa2950c49d7 Mon Sep 17 00:00:00 2001
From: "erik.corry@gmail.com"
 <erik.corry@gmail.com@ce2b1a6d-e550-0410-aec6-3dcde31c8c00>
Date: Fri, 16 Mar 2012 14:13:22 +0000
Subject: [PATCH] Record the addresses of pages that are unmapped to aid in
 post mortem crash dump analysis. Review URL:
 https://chromiumcodereview.appspot.com/9700061

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11071 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
---
 src/heap.cc         | 16 ++++++++++++++++
 src/heap.h          |  9 ++++++++-
 src/mark-compact.cc |  1 -
 src/spaces.cc       |  3 +++
 4 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/src/heap.cc b/src/heap.cc
index be302acbee..259dc31e88 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -104,6 +104,7 @@ Heap::Heap()
       gc_post_processing_depth_(0),
       ms_count_(0),
       gc_count_(0),
+      remembered_unmapped_pages_index_(0),
       unflattened_strings_length_(0),
 #ifdef DEBUG
       allocation_allowed_(true),
@@ -6971,4 +6972,19 @@ void Heap::FreeQueuedChunks() {
   chunks_queued_for_free_ = NULL;
 }
 
+
+void Heap::RememberUnmappedPage(Address page, bool compacted) {
+  uintptr_t p = reinterpret_cast<uintptr_t>(page);
+  // Tag the page pointer to make it findable in the dump file.
+  if (compacted) {
+    p ^= 0xc1ead & (Page::kPageSize - 1);  // Cleared.
+  } else {
+    p ^= 0x1d1ed & (Page::kPageSize - 1);  // I died.
+  }
+  remembered_unmapped_pages_[remembered_unmapped_pages_index_] =
+      reinterpret_cast<Address>(p);
+  remembered_unmapped_pages_index_++;
+  remembered_unmapped_pages_index_ %= kRememberedUnmappedPages;
+}
+
 } }  // namespace v8::internal
diff --git a/src/heap.h b/src/heap.h
index df3717e4fa..ef9ea1d6c6 100644
--- a/src/heap.h
+++ b/src/heap.h
@@ -1583,6 +1583,9 @@ class Heap {
     set_construct_stub_deopt_pc_offset(Smi::FromInt(pc_offset));
   }
 
+  // For post mortem debugging.
+  void RememberUnmappedPage(Address page, bool compacted);
+
  private:
   Heap();
 
@@ -1634,6 +1637,11 @@ class Heap {
   int ms_count_;  // how many mark-sweep collections happened
   unsigned int gc_count_;  // how many gc happened
 
+  // For post mortem debugging.
+  static const int kRememberedUnmappedPages = 128;
+  int remembered_unmapped_pages_index_;
+  Address remembered_unmapped_pages_[kRememberedUnmappedPages];
+
   // Total length of the strings we failed to flatten since the last GC.
   int unflattened_strings_length_;
 
@@ -1781,7 +1789,6 @@ class Heap {
 
   inline void UpdateOldSpaceLimits();
 
-
   // Allocate an uninitialized object in map space.  The behavior is identical
   // to Heap::AllocateRaw(size_in_bytes, MAP_SPACE), except that (a) it doesn't
   // have to test the allocation space argument and (b) can reduce code size
diff --git a/src/mark-compact.cc b/src/mark-compact.cc
index 17be2234c7..b956e73e10 100644
--- a/src/mark-compact.cc
+++ b/src/mark-compact.cc
@@ -3427,7 +3427,6 @@ void MarkCompactCollector::EvacuateNewSpaceAndCandidates() {
     space->Free(p->area_start(), p->area_size());
     p->set_scan_on_scavenge(false);
     slots_buffer_allocator_.DeallocateChain(p->slots_buffer_address());
-    p->ClearEvacuationCandidate();
     p->ResetLiveBytes();
     space->ReleasePage(p);
   }
diff --git a/src/spaces.cc b/src/spaces.cc
index d7061a1a79..2f3bb9bfb0 100644
--- a/src/spaces.cc
+++ b/src/spaces.cc
@@ -594,6 +594,9 @@ void MemoryAllocator::Free(MemoryChunk* chunk) {
     PerformAllocationCallback(space, kAllocationActionFree, chunk->size());
   }
 
+  isolate_->heap()->RememberUnmappedPage(
+      reinterpret_cast<Address>(chunk), chunk->IsEvacuationCandidate());
+
   delete chunk->slots_buffer();
   delete chunk->skip_list();