Use MemoryChunk-based allocation for deoptimization entry code

src/spaces.cc

 // 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 189 matching lines @@
     if (requested <= allocation_list_[current_allocation_block_index_].size) {
       return;  // Found a large enough allocation block.
     }
   }
 
   // Code range is full or too fragmented.
   V8::FatalProcessOutOfMemory("CodeRange::GetNextAllocationBlock");
 }
 
 
-
 Address CodeRange::AllocateRawMemory(const size_t requested,
-                                     size_t* allocated) {
+                                     size_t* allocated,
+                                     size_t commit_body_size) {
+  ASSERT(commit_body_size <= requested);
   ASSERT(current_allocation_block_index_ < allocation_list_.length());
   if (requested > allocation_list_[current_allocation_block_index_].size) {
     // Find an allocation block large enough.  This function call may
     // call V8::FatalProcessOutOfMemory if it cannot find a large enough block.
     GetNextAllocationBlock(requested);
   }
   // Commit the requested memory at the start of the current allocation block.
   size_t aligned_requested = RoundUp(requested, MemoryChunk::kAlignment);
   FreeBlock current = allocation_list_[current_allocation_block_index_];
   if (aligned_requested >= (current.size - Page::kPageSize)) {
     // Don't leave a small free block, useless for a large object or chunk.
     *allocated = current.size;
   } else {
     *allocated = aligned_requested;
   }
   ASSERT(*allocated <= current.size);
   ASSERT(IsAddressAligned(current.start, MemoryChunk::kAlignment));
   if (!MemoryAllocator::CommitCodePage(code_range_,
                                        current.start,
-                                       *allocated)) {
+                                       *allocated,
+                                       commit_body_size)) {
     *allocated = 0;
     return NULL;
   }
   allocation_list_[current_allocation_block_index_].start += *allocated;
   allocation_list_[current_allocation_block_index_].size -= *allocated;
   if (*allocated == current.size) {
     GetNextAllocationBlock(0);  // This block is used up, get the next one.
   }
   return current.start;
 }
 
 
+bool CodeRange::CommitRawMemory(Address start, size_t length) {
+  // Commit page body (executable).
+  if (!code_range_->Commit(start, length, true)) return false;

[danno, 2013/01/17 10:49:55]

how about just:

return code_range_->Commit(start, length, true);

[haitao.feng, 2013/01/17 14:20:33]

Done.

+  return true;
+}
+
+
 void CodeRange::FreeRawMemory(Address address, size_t length) {
   ASSERT(IsAddressAligned(address, MemoryChunk::kAlignment));
   free_list_.Add(FreeBlock(address, length));
   code_range_->Uncommit(address, length);
 }
 
 
 void CodeRange::TearDown() {
     delete code_range_;  // Frees all memory in the virtual memory range.
     code_range_ = NULL;
@@ skipping 84 matching lines @@
 }
 
 
 Address MemoryAllocator::ReserveAlignedMemory(size_t size,
                                               size_t alignment,
                                               VirtualMemory* controller) {
   VirtualMemory reservation(size, alignment);
 
   if (!reservation.IsReserved()) return NULL;
   size_ += reservation.size();
-  Address base = RoundUp(static_cast<Address>(reservation.address()),
-                         alignment);
+  Address base = static_cast<Address>(reservation.address());
   controller->TakeControl(&reservation);
   return base;
 }
 
 
 Address MemoryAllocator::AllocateAlignedMemory(size_t size,

[danno, 2013/01/17 10:49:55]

nit: "requested_size" is a better name

[haitao.feng, 2013/01/17 14:20:33]

Done.

                                                size_t alignment,
+                                               size_t commit_body_size,

[danno, 2013/01/17 10:49:55]

nit: "commit_size" is a better name
nit: could you make this the second parameter?, i.e.:

AllocateAlignedMemory(reserved_size, commit_size, alignment, ...)

[haitao.feng, 2013/01/17 14:20:33]

Done.

[haitao.feng, 2013/01/17 14:20:33]

Done.

                                                Executability executable,
                                                VirtualMemory* controller) {
+  ASSERT(commit_body_size <= size);
   VirtualMemory reservation;
   Address base = ReserveAlignedMemory(size, alignment, &reservation);
   if (base == NULL) return NULL;
 
   if (executable == EXECUTABLE) {
-    if (!CommitCodePage(&reservation, base, size)) {
+    if (!CommitCodePage(&reservation, base, size, commit_body_size)) {
       base = NULL;
     }
   } else {
-    if (!reservation.Commit(base, size, false)) {
+    size_t commit_size = MemoryChunk::kObjectStartOffset + commit_body_size;
+    if (!reservation.Commit(base, commit_size, false)) {
       base = NULL;
     }
   }
 
   if (base == NULL) {
     // Failed to commit the body. Release the mapping and any partially
     // commited regions inside it.
     reservation.Release();
     return NULL;
   }
@@ skipping 83 matching lines @@
   }
 
   if (owner == heap->old_data_space()) {
     chunk->SetFlag(CONTAINS_ONLY_DATA);
   }
 
   return chunk;
 }
 
 
+bool MemoryChunk::CommitBody(size_t body_size, Executability executable) {
+  // Already committed, no uncommitment
+  if (body_size <= (area_end_ - area_start_)) return true;

[danno, 2013/01/17 10:49:55]

The problem with using area_end is that you change it later. This is brittle,
since a MemoryChunk's reservation never changes, just how much is committed. If
you change area_end_, you can commit off the end of the reserved area, because
there is no way that you can validate body_size (i.e. there actually should be a
ASSERT(body_size <= area_end_ - area_start_) statement in this method. That's
why I suggested adding commited_size_, and I still think that's a good idea.
area_end_ should be immutable.

[haitao.feng, 2013/01/17 14:20:33]

How about "ASSERT(body_size <= static_cast<size_t>(address() + size_ -
area_start_))"? From my reading, the memory space between area_start_ and
area_end_ should be iterated. If area_end_ is not committed, we could not access
it.

+
+  size_t length = body_size - (area_end_ - area_start_);
+  if (reservation_.IsReserved()) {
+      if (!reservation_.Commit(area_end_, length, executable == EXECUTABLE)) {
+        return false;
+      }
+  } else {
+    CodeRange* code_range = heap_->isolate()->code_range();
+    ASSERT(code_range->exists() && (executable == EXECUTABLE));
+    if (!code_range->CommitRawMemory(area_end_, length))  return false;
+  }
+
+  if (Heap::ShouldZapGarbage()) {
+    heap_->isolate()->memory_allocator()->ZapBlock(area_end_, length);
+  }
+
+  area_end_ = area_start_ + body_size;
+
+  return true;
+}
+
+
 void MemoryChunk::InsertAfter(MemoryChunk* other) {
   next_chunk_ = other->next_chunk_;
   prev_chunk_ = other;
   other->next_chunk_->prev_chunk_ = this;
   other->next_chunk_ = this;
 }
 
 
 void MemoryChunk::Unlink() {
   if (!InNewSpace() && IsFlagSet(SCAN_ON_SCAVENGE)) {
     heap_->decrement_scan_on_scavenge_pages();
     ClearFlag(SCAN_ON_SCAVENGE);
   }
   next_chunk_->prev_chunk_ = prev_chunk_;
   prev_chunk_->next_chunk_ = next_chunk_;
   prev_chunk_ = NULL;
   next_chunk_ = NULL;
 }
 
 
-MemoryChunk* MemoryAllocator::AllocateChunk(intptr_t body_size,
+MemoryChunk* MemoryAllocator::AllocateChunk(intptr_t reserve_body_size,
+                                            intptr_t commit_body_size,
                                             Executability executable,
                                             Space* owner) {
+  ASSERT(commit_body_size <= reserve_body_size);
+
   size_t chunk_size;
   Heap* heap = isolate_->heap();
   Address base = NULL;
   VirtualMemory reservation;
   Address area_start = NULL;
   Address area_end = NULL;
 
   if (executable == EXECUTABLE) {
-    chunk_size = RoundUp(CodePageAreaStartOffset() + body_size,
+    chunk_size = RoundUp(CodePageAreaStartOffset() + reserve_body_size,
                          OS::CommitPageSize()) + CodePageGuardSize();
 
     // Check executable memory limit.
     if (size_executable_ + chunk_size > capacity_executable_) {
       LOG(isolate_,
           StringEvent("MemoryAllocator::AllocateRawMemory",
                       "V8 Executable Allocation capacity exceeded"));
       return NULL;
     }
 
     // Allocate executable memory either from code range or from the
     // OS.
     if (isolate_->code_range()->exists()) {
-      base = isolate_->code_range()->AllocateRawMemory(chunk_size, &chunk_size);
+      base = isolate_->code_range()->AllocateRawMemory(chunk_size,
+                                                       &chunk_size,
+                                                       commit_body_size);
       ASSERT(IsAligned(reinterpret_cast<intptr_t>(base),
                        MemoryChunk::kAlignment));
       if (base == NULL) return NULL;
       size_ += chunk_size;
       // Update executable memory size.
       size_executable_ += chunk_size;
     } else {
       base = AllocateAlignedMemory(chunk_size,
                                    MemoryChunk::kAlignment,
+                                   commit_body_size,
                                    executable,
                                    &reservation);
       if (base == NULL) return NULL;
       // Update executable memory size.
       size_executable_ += reservation.size();
     }
 
     if (Heap::ShouldZapGarbage()) {
       ZapBlock(base, CodePageGuardStartOffset());
-      ZapBlock(base + CodePageAreaStartOffset(), body_size);
+      ZapBlock(base + CodePageAreaStartOffset(), commit_body_size);
     }
 
     area_start = base + CodePageAreaStartOffset();
-    area_end = area_start + body_size;
+    area_end = area_start + commit_body_size;

[danno, 2013/01/17 10:49:55]

area_end should always be the end of the reserved space, not the committed
space.

[haitao.feng, 2013/01/17 14:20:33]

The end could be calculated by address() + size_. 

   } else {
-    chunk_size = MemoryChunk::kObjectStartOffset + body_size;
+    chunk_size = MemoryChunk::kObjectStartOffset + reserve_body_size;
     base = AllocateAlignedMemory(chunk_size,
                                  MemoryChunk::kAlignment,
+                                 commit_body_size,
                                  executable,
                                  &reservation);
 
     if (base == NULL) return NULL;
 
     if (Heap::ShouldZapGarbage()) {
-      ZapBlock(base, chunk_size);
+      ZapBlock(base, MemoryChunk::kObjectStartOffset + commit_body_size);
     }
 
     area_start = base + Page::kObjectStartOffset;
-    area_end = base + chunk_size;
+    area_end = area_start + commit_body_size;
   }
 
+  // Use chunk_size for statistics and callbacks as the reserved
+  // but uncommitted memory regions are only meaningful for this allocated
+  // memory trunk.

[danno, 2013/01/17 10:49:55]

nit: I don't know what you mean by "allocated memory trunk". How about:

Use chunk_size for statistics and callbacks because we assume that they treat
reserved but not-yet committed memory regions of chunks as allocated.

[haitao.feng, 2013/01/17 14:20:33]

Done.

   isolate_->counters()->memory_allocated()->
       Increment(static_cast<int>(chunk_size));
 
   LOG(isolate_, NewEvent("MemoryChunk", base, chunk_size));
   if (owner != NULL) {
     ObjectSpace space = static_cast<ObjectSpace>(1 << owner->identity());
     PerformAllocationCallback(space, kAllocationActionAllocate, chunk_size);
   }
 
   MemoryChunk* result = MemoryChunk::Initialize(heap,
                                                 base,
                                                 chunk_size,
                                                 area_start,
                                                 area_end,
                                                 executable,
                                                 owner);
   result->set_reserved_memory(&reservation);
   return result;
 }
 
 
 Page* MemoryAllocator::AllocatePage(intptr_t size,
                                     PagedSpace* owner,
                                     Executability executable) {
-  MemoryChunk* chunk = AllocateChunk(size, executable, owner);
+  MemoryChunk* chunk = AllocateChunk(size, size, executable, owner);
 
   if (chunk == NULL) return NULL;
 
   return Page::Initialize(isolate_->heap(), chunk, executable, owner);
 }
 
 
 LargePage* MemoryAllocator::AllocateLargePage(intptr_t object_size,
                                               Space* owner,
                                               Executability executable) {
-  MemoryChunk* chunk = AllocateChunk(object_size, executable, owner);
+  MemoryChunk* chunk = AllocateChunk(object_size,
+                                     object_size,
+                                     executable,
+                                     owner);
   if (chunk == NULL) return NULL;
   return LargePage::Initialize(isolate_->heap(), chunk);
 }
 
 
 void MemoryAllocator::Free(MemoryChunk* chunk) {
   LOG(isolate_, DeleteEvent("MemoryChunk", chunk));
   if (chunk->owner() != NULL) {
     ObjectSpace space =
         static_cast<ObjectSpace>(1 << chunk->owner()->identity());
@@ skipping 123 matching lines @@
 
 int MemoryAllocator::CodePageAreaEndOffset() {
   // We are guarding code pages: the last OS page will be protected as
   // non-writable.
   return Page::kPageSize - static_cast<int>(OS::CommitPageSize());
 }
 
 
 bool MemoryAllocator::CommitCodePage(VirtualMemory* vm,
                                      Address start,
-                                     size_t size) {
+                                     size_t size,

[danno, 2013/01/17 10:49:55]

I think it's clearer if you swap the order of the parameters here and call them
"reserved_size" and "committed_size". I also think that the name of the function
is not quite right, I think it should be renamed to "CommitExecutableMemory"

[haitao.feng, 2013/01/17 14:20:33]

Done.

+                                     size_t body_size) {
   // Commit page header (not executable).
   if (!vm->Commit(start,
                   CodePageGuardStartOffset(),
                   false)) {
     return false;
   }
 
   // Create guard page after the header.
   if (!vm->Guard(start + CodePageGuardStartOffset())) {
     return false;
   }
 
   // Commit page body (executable).
-  size_t area_size = size - CodePageAreaStartOffset() - CodePageGuardSize();
   if (!vm->Commit(start + CodePageAreaStartOffset(),
-                  area_size,
+                  body_size,
                   true)) {
     return false;
   }
 
-  // Create guard page after the allocatable area.
-  if (!vm->Guard(start + CodePageAreaStartOffset() + area_size)) {
+  // Create guard page before the end.
+  if (!vm->Guard(start + size - CodePageGuardSize())) {
     return false;
   }
 
   return true;
 }
 
 
 // -----------------------------------------------------------------------------
 // MemoryChunk implementation
 
@@ skipping 2215 matching lines @@
     object->ShortPrint();
     PrintF("\n");
   }
   printf(" --------------------------------------\n");
   printf(" Marked: %x, LiveCount: %x\n", mark_size, LiveBytes());
 }
 
 #endif  // DEBUG
 
 } }  // namespace v8::internal