*** old/src/share/vm/memory/heap.cpp	Wed Feb  5 17:12:39 2014
--- new/src/share/vm/memory/heap.cpp	Wed Feb  5 17:12:39 2014

*** 51,61 ****
--- 51,61 ----
    assert(beg <  end && end <= _number_of_committed_segments, "interval end   out of bounds");
    // setup _segmap pointers for faster indexing
    address p = (address)_segmap.low() + beg;
    address q = (address)_segmap.low() + end;
    // initialize interval
!   while (p < q) *p++ = 0xFF;
!   while (p < q) *p++ = free_sentinel;
  }
  
  
  void CodeHeap::mark_segmap_as_used(size_t beg, size_t end) {
    assert(0   <= beg && beg <  _number_of_committed_segments, "interval begin out of bounds");

*** 65,75 ****
--- 65,75 ----
    address q = (address)_segmap.low() + end;
    // initialize interval
    int i = 0;
    while (p < q) {
      *p++ = i++;
!     if (i == 0xFF) i = 1;
!     if (i == free_sentinel) i = 1;
    }
  }
  
  
  static size_t align_to_page_size(size_t size) {

*** 137,151 ****
--- 137,146 ----
    clear();
    return true;
  }
  
  
  void CodeHeap::release() {
    Unimplemented();
  }
  
  
  bool CodeHeap::expand_by(size_t size) {
    // expand _memory space
    size_t dm = align_to_page_size(_memory.committed_size() + size) - _memory.committed_size();
    if (dm > 0) {
      char* base = _memory.low() + _memory.committed_size();

*** 155,207 ****
--- 150,193 ----
      _number_of_committed_segments = size_to_segments(_memory.committed_size());
      assert(_number_of_reserved_segments == size_to_segments(_memory.reserved_size()), "number of reserved segments should not change");
      assert(_number_of_reserved_segments >= _number_of_committed_segments, "just checking");
      // expand _segmap space
      size_t ds = align_to_page_size(_number_of_committed_segments) - _segmap.committed_size();
!     if ((ds > 0) && !_segmap.expand_by(ds)) {
-       if (!_segmap.expand_by(ds)) return false;
      }
      assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "just checking");
      // initialize additional segmap entries
      mark_segmap_as_free(i, _number_of_committed_segments);
    }
    return true;
  }
  
  
  void CodeHeap::shrink_by(size_t size) {
    Unimplemented();
  }
  
  
  void CodeHeap::clear() {
    _next_segment = 0;
    mark_segmap_as_free(0, _number_of_committed_segments);
  }
  
  
  void* CodeHeap::allocate(size_t instance_size, bool is_critical) {
!   size_t number_of_segments = size_to_segments(instance_size + sizeof(HeapBlock));
!   size_t number_of_segments = size_to_segments(instance_size + header_size());
    assert(segments_to_size(number_of_segments) >= sizeof(FreeBlock), "not enough room for FreeList");
  
!   // First check if we can satify request from freelist
!   debug_only(verify());
!   // First check if we can satisfy request from freelist
!   NOT_PRODUCT(verify());
    HeapBlock* block = search_freelist(number_of_segments, is_critical);
!   debug_only(if (VerifyCodeCacheOften) verify());
!   NOT_PRODUCT(verify());
+ 
    if (block != NULL) {
      assert(block->length() >= number_of_segments && block->length() < number_of_segments + CodeCacheMinBlockLength, "sanity check");
      assert(!block->free(), "must be marked free");
  #ifdef ASSERT
      memset((void *)block->allocated_space(), badCodeHeapNewVal, instance_size);
  #endif
+     DEBUG_ONLY(memset((void*)block->allocated_space(), badCodeHeapNewVal, instance_size));
      return block->allocated_space();
    }
  
    // Ensure minimum size for allocation to the heap.
    if (number_of_segments < CodeCacheMinBlockLength) {
      number_of_segments = CodeCacheMinBlockLength;
    }
+   number_of_segments = MAX2((int)CodeCacheMinBlockLength, (int)number_of_segments);
  
    if (!is_critical) {
      // Make sure the allocation fits in the unallocated heap without using
      // the CodeCacheMimimumFreeSpace that is reserved for critical allocations.
      if (segments_to_size(number_of_segments) > (heap_unallocated_capacity() - CodeCacheMinimumFreeSpace)) {

*** 213,225 ****
--- 199,209 ----
    if (_next_segment + number_of_segments <= _number_of_committed_segments) {
      mark_segmap_as_used(_next_segment, _next_segment + number_of_segments);
      HeapBlock* b =  block_at(_next_segment);
      b->initialize(number_of_segments);
      _next_segment += number_of_segments;
  #ifdef ASSERT
      memset((void *)b->allocated_space(), badCodeHeapNewVal, instance_size);
  #endif
+     DEBUG_ONLY(memset((void *)b->allocated_space(), badCodeHeapNewVal, instance_size));
      return b->allocated_space();
    } else {
      return NULL;
    }
  }

*** 228,259 ****
--- 212,271 ----
  void CodeHeap::deallocate(void* p) {
    assert(p == find_start(p), "illegal deallocation");
    // Find start of HeapBlock
    HeapBlock* b = (((HeapBlock *)p) - 1);
    assert(b->allocated_space() == p, "sanity check");
  #ifdef ASSERT
    memset((void *)b->allocated_space(),
           badCodeHeapFreeVal,
           segments_to_size(b->length()) - sizeof(HeapBlock));
  #endif
+   DEBUG_ONLY(memset((void *)b->allocated_space(), badCodeHeapFreeVal,
+              segments_to_size(b->length()) - sizeof(HeapBlock)));
    add_to_freelist(b);
  
    debug_only(if (VerifyCodeCacheOften) verify());
+   NOT_PRODUCT(verify());
  }
  
  
+ /**
+  * Uses segment map to find the the start (header) of a nmethod. This works as follows:
+  * The memory of the code cache is divided into 'segments'. The size of a segment is
+  * determined by -XX:CodeCacheSegmentSize=XX. Allocation in the code cache can only
+  * happen at segment boundaries. A pointer in the code cache can be mapped to a segment
+  * by calling segment_for(addr). Each time memory is requested from the code cache,
+  * the segmap is updated accordingly. See the following example, which illustrates the
+  * state of code cache and the segment map: (seg -> segment, nm ->nmethod)
+  *
+  *          code cache          segmap
+  *         -----------        ---------
+  * seg 1   | nm 1    |   ->   | 0     |
+  * seg 2   | nm 1    |   ->   | 1     |
+  * ...     | nm 1    |   ->   | ..    |
+  * seg m   | nm 2    |   ->   | 0     |
+  * seg m+1 | nm 2    |   ->   | 1     |
+  * ...     | nm 2    |   ->   | 2     |
+  * ...     | nm 2    |   ->   | ..    |
+  * ...     | nm 2    |   ->   | 0xFE  |
+  * seg m+n | nm 2    |   ->   | 1     |
+  * ...     | nm 2    |   ->   |       |
+  *
+  * A value of '0' in the segmap indicates that this segment contains the beginning of
+  * an nmethod. Let's walk through a simple example: If we want to find the start of
+  * an nmethod that falls into seg 2, we read the value of the segmap[2]. The value
+  * is an offset that points to the segment that contains the start of the nmethod.
+  * Another example: If we want to get the start of nm 2, and we happen to get a pointer
+  * that points to seg m+n, we first read seg[n+m], which returns '1'. So we have to
+  * do one more read of the segmap[m+n-1] to finally get the segment header.
+  */
  void* CodeHeap::find_start(void* p) const {
    if (!contains(p)) {
      return NULL;
    }
!   size_t seg_idx = segment_for(p);
!   address b = (address)_segmap.low();
!   if (b[i] == 0xFF) {
!   address seg_map = (address)_segmap.low();
!   if (is_segment_unused(seg_map[seg_idx])) {
      return NULL;
    }
!   while (b[i] > 0) i -= (int)b[i];
!   HeapBlock* h = block_at(i);
!   while (seg_map[seg_idx] > 0) {
!     seg_idx -= (int)seg_map[seg_idx];
+   }
+ 
+   HeapBlock* h = block_at(seg_idx);
    if (h->free()) {
      return NULL;
    }
    return h->allocated_space();
  }

*** 270,280 ****
--- 282,292 ----
    // equal to alignment_offset (mod alignment_unit).
    return sizeof(HeapBlock) & (_segment_size - 1);
  }
  
  // Finds the next free heapblock. If the current one is free, that it returned
! void* CodeHeap::next_free(HeapBlock *b) const {
! void* CodeHeap::next_free(HeapBlock* b) const {
    // Since free blocks are merged, there is max. on free block
    // between two used ones
    if (b != NULL && b->free()) b = next_block(b);
    assert(b == NULL || !b->free(), "must be in use or at end of heap");
    return (b == NULL) ? NULL : b->allocated_space();

*** 285,295 ****
--- 297,307 ----
    if (_next_segment > 0)
      return block_at(0);
    return NULL;
  }
  
! HeapBlock *CodeHeap::block_start(void *q) const {
! HeapBlock* CodeHeap::block_start(void* q) const {
    HeapBlock* b = (HeapBlock*)find_start(q);
    if (b == NULL) return NULL;
    return b - 1;
  }
  

*** 323,333 ****
--- 335,345 ----
    return segments_to_size(_number_of_reserved_segments - _next_segment);
  }
  
  // Free list management
  
! FreeBlock *CodeHeap::following_block(FreeBlock *b) {
! FreeBlock* CodeHeap::following_block(FreeBlock *b) {
    return (FreeBlock*)(((address)b) + _segment_size * b->length());
  }
  
  // Inserts block b after a
  void CodeHeap::insert_after(FreeBlock* a, FreeBlock* b) {

*** 341,364 ****
--- 353,379 ----
    merge_right(b); // Try to make b bigger
    merge_right(a); // Try to make a include b
  }
  
  // Try to merge this block with the following block
! void CodeHeap::merge_right(FreeBlock *a) {
! bool CodeHeap::merge_right(FreeBlock* a) {
    assert(a->free(), "must be a free block");
    if (following_block(a) == a->link()) {
      assert(a->link() != NULL && a->link()->free(), "must be free too");
      // Update block a to include the following block
      a->set_length(a->length() + a->link()->length());
      a->set_link(a->link()->link());
      // Update find_start map
      size_t beg = segment_for(a);
      mark_segmap_as_used(beg, beg + a->length());
+     return true;
    }
+   return false;
  }
  
  void CodeHeap::add_to_freelist(HeapBlock *a) {
+ 
+ void CodeHeap::add_to_freelist(HeapBlock* a) {
    FreeBlock* b = (FreeBlock*)a;
    assert(b != _freelist, "cannot be removed twice");
  
    // Mark as free and update free space count
    _freelist_segments += b->length();

*** 369,428 ****
--- 384,451 ----
      _freelist = b;
      b->set_link(NULL);
      return;
    }
  
+   // Since the freelist is ordered (smaller->larger) and the element we want to insert
+   // into the freelist is smaller than the first element, we can simply add 'b' as the
+   // first element and we are done.
+   if (b < _freelist) {
+     // Insert first in list
+     b->set_link(_freelist);
+     _freelist = b;
+     merge_right(_freelist);
+     return;
+   }
+ 
    // Scan for right place to put into list. List
-   // is sorted by increasing addresseses
!   FreeBlock* prev = NULL;
!   FreeBlock* cur  = _freelist;
!   FreeBlock* prev = _freelist;
!   FreeBlock* cur  = _freelist->link();
    while(cur != NULL && cur < b) {
!     assert(prev == NULL || prev < cur, "must be ordered");
!     assert(prev < cur, "Freelist must be ordered");
      prev = cur;
      cur  = cur->link();
    }
  
    assert( (prev == NULL && b < _freelist) ||
            (prev < b && (cur == NULL || b < cur)), "list must be ordered");
  
    if (prev == NULL) {
      // Insert first in list
      b->set_link(_freelist);
      _freelist = b;
      merge_right(_freelist);
    } else {
+   assert((prev < b) && (cur == NULL || b < cur), "free-list must be ordered");
    insert_after(prev, b);
    }
  }
  
  // Search freelist for an entry on the list with the best fit
  // Return NULL if no one was found
+ /**
+  * Search freelist for an entry on the list with the best fit.
+  * @return NULL, if no one was found
+  */
  FreeBlock* CodeHeap::search_freelist(size_t length, bool is_critical) {
!   FreeBlock *best_block = NULL;
!   FreeBlock *best_prev  = NULL;
!   FreeBlock* best_block = NULL;
!   FreeBlock* best_prev  = NULL;
    size_t     best_length = 0;
  
+   FreeBlock* prev = NULL;
+   FreeBlock* cur = _freelist;
+   const size_t critical_boundary = (size_t)high_boundary() - CodeCacheMinimumFreeSpace;
+ 
    // Search for smallest block which is bigger than length
    FreeBlock *prev = NULL;
    FreeBlock *cur = _freelist;
    while(cur != NULL) {
      size_t l = cur->length();
!     if (l >= length && (best_block == NULL || best_length > l)) {
  
!     if (l >= length && (best_block == NULL || l < best_length )) {
        // Non critical allocations are not allowed to use the last part of the code heap.
        if (!is_critical) {
          // Make sure the end of the allocation doesn't cross into the last part of the code heap
          if (((size_t)cur + length) > ((size_t)high_boundary() - CodeCacheMinimumFreeSpace)) {
            // the freelist is sorted by address - if one fails, all consecutive will also fail.
+       // Make sure the end of the allocation doesn't cross into the last part of the code heap.
+       if (!is_critical && (((size_t)cur + length) > critical_boundary)) {
+         // The freelist is sorted by address - if one fails, all consecutive will also fail.
          break;
        }
        }
  
        // Remember best block, its previous element, and its length
        best_block = cur;
        best_prev  = prev;
        best_length = best_block->length();
+ 
+       // Found best fit, since we are not allowed to have less than CodeCacheMinBlockLength number of
+       // free segments.
+       if ((best_length - length) < CodeCacheMinBlockLength) {
+         break;
+       }
      }
  
      // Next element in list
      prev = cur;
      cur  = cur->link();

*** 431,451 ****
--- 454,472 ----
    if (best_block == NULL) {
      // None found
      return NULL;
    }
  
    assert((best_prev == NULL && _freelist == best_block ) ||
           (best_prev != NULL && best_prev->link() == best_block), "sanity check");
  
    // Exact (or at least good enough) fit. Remove from list.
    // Don't leave anything on the freelist smaller than CodeCacheMinBlockLength.
    if (best_length < length + CodeCacheMinBlockLength) {
      length = best_length;
      if (best_prev == NULL) {
        assert(_freelist == best_block, "sanity check");
        _freelist = _freelist->link();
      } else {
+       assert((best_prev->link() == best_block), "sanity check");
        // Unmap element
        best_prev->set_link(best_block->link());
      }
    } else {
      // Truncate block and return a pointer to the following block

*** 469,503 ****
--- 490,525 ----
  
  void CodeHeap::print() {
    tty->print_cr("The Heap");
  }
  
  #endif
  
  void CodeHeap::verify() {
    // Count the number of blocks on the freelist, and the amount of space
    // represented.
    int count = 0;
+   if (VerifyCodeCache) {
      size_t len = 0;
+     int count = 0;
      for(FreeBlock* b = _freelist; b != NULL; b = b->link()) {
        len += b->length();
        count++;
+       // Check if we have merged all free blocks
+       assert(merge_right(b) == false, "Missed merging opportunity");
      }
  
      // Verify that freelist contains the right amount of free space
!   //  guarantee(len == _freelist_segments, "wrong freelist");
!     assert(len == _freelist_segments, "wrong freelist");
+ 
+     for(HeapBlock* h = first_block(); h != NULL; h = next_block(h)) {
+       if (h->free()) count--;
+     }
+     // Verify that the freelist contains the same number of blocks
+     // than free blocks found on the full list.
+     assert(count == 0, "missing free blocks");
  
      // Verify that the number of free blocks is not out of hand.
      static int free_block_threshold = 10000;
      if (count > free_block_threshold) {
        warning("CodeHeap: # of free blocks > %d", free_block_threshold);
        // Double the warning limit
        free_block_threshold *= 2;
      }
  
    // Verify that the freelist contains the same number of free blocks that is
    // found on the full list.
    for(HeapBlock *h = first_block(); h != NULL; h = next_block(h)) {
      if (h->free()) count--;
    }
    //  guarantee(count == 0, "missing free blocks");
  }
+ 
+ #endif