--- old/src/share/vm/memory/heap.cpp 2014-02-04 16:00:32.214625768 +0100 +++ new/src/share/vm/memory/heap.cpp 2014-02-04 16:00:32.094625771 +0100 @@ -53,7 +53,7 @@ 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; } @@ -67,7 +67,7 @@ int i = 0; while (p < q) { *p++ = i++; - if (i == 0xFF) i = 1; + if (i == free_sentinel) i = 1; } } @@ -139,11 +139,6 @@ } -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(); @@ -157,8 +152,8 @@ 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) { - if (!_segmap.expand_by(ds)) return false; + if ((ds > 0) && !_segmap.expand_by(ds)) { + return false; } assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "just checking"); // initialize additional segmap entries @@ -167,12 +162,6 @@ 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); @@ -180,26 +169,23 @@ 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 @@ -215,9 +201,7 @@ 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; @@ -230,28 +214,56 @@ // 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 i = segment_for(p); - address b = (address)_segmap.low(); - if (b[i] == 0xFF) { + size_t seg_idx = segment_for(p); + 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; } @@ -272,7 +284,7 @@ } // 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); @@ -287,7 +299,7 @@ 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; @@ -325,7 +337,7 @@ // Free list management -FreeBlock *CodeHeap::following_block(FreeBlock *b) { +FreeBlock* CodeHeap::following_block(FreeBlock *b) { return (FreeBlock*)(((address)b) + _segment_size * b->length()); } @@ -343,7 +355,7 @@ } // 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"); @@ -353,10 +365,13 @@ // 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"); @@ -371,56 +386,64 @@ return; } - // Scan for right place to put into list. List - // is sorted by increasing addresseses - FreeBlock* prev = NULL; - FreeBlock* cur = _freelist; - while(cur != NULL && cur < b) { - assert(prev == NULL || prev < cur, "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) { + // 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); - } else { - insert_after(prev, b); + return; + } + + // Scan for right place to put into list. List + // is sorted by increasing addresses + FreeBlock* prev = _freelist; + FreeBlock* cur = _freelist->link(); + while(cur != NULL && cur < b) { + assert(prev < cur, "Freelist must be ordered"); + prev = cur; + cur = cur->link(); } + 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; - size_t best_length = 0; + 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. - break; - } + // 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 @@ -433,9 +456,6 @@ 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) { @@ -444,6 +464,7 @@ 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()); } @@ -474,30 +495,31 @@ #endif void CodeHeap::verify() { - // Count the number of blocks on the freelist, and the amount of space - // represented. - int count = 0; - size_t len = 0; - for(FreeBlock* b = _freelist; b != NULL; b = b->link()) { - len += b->length(); - count++; - } - - // Verify that freelist contains the right amount of free space - // guarantee(len == _freelist_segments, "wrong freelist"); - - // 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--; + 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 + 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; + } } - // guarantee(count == 0, "missing free blocks"); }