| /* |
| * Copyright (c) 1997, 2019, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| * |
| */ |
| |
| #include "precompiled.hpp" |
| #include "memory/heap.hpp" |
| #include "oops/oop.inline.hpp" |
| #include "runtime/os.hpp" |
| #include "services/memTracker.hpp" |
| #include "utilities/align.hpp" |
| |
| size_t CodeHeap::header_size() { |
| return sizeof(HeapBlock); |
| } |
| |
| |
| // Implementation of Heap |
| |
| CodeHeap::CodeHeap(const char* name, const int code_blob_type) |
| : _code_blob_type(code_blob_type) { |
| _name = name; |
| _number_of_committed_segments = 0; |
| _number_of_reserved_segments = 0; |
| _segment_size = 0; |
| _log2_segment_size = 0; |
| _next_segment = 0; |
| _freelist = NULL; |
| _last_insert_point = NULL; |
| _freelist_segments = 0; |
| _freelist_length = 0; |
| _max_allocated_capacity = 0; |
| _blob_count = 0; |
| _nmethod_count = 0; |
| _adapter_count = 0; |
| _full_count = 0; |
| _fragmentation_count = 0; |
| } |
| |
| // Dummy initialization of template array. |
| char CodeHeap::segmap_template[] = {0}; |
| |
| // This template array is used to (re)initialize the segmap, |
| // replacing a 1..254 loop. |
| void CodeHeap::init_segmap_template() { |
| assert(free_sentinel == 255, "Segment map logic changed!"); |
| for (int i = 0; i <= free_sentinel; i++) { |
| segmap_template[i] = i; |
| } |
| } |
| |
| // The segmap is marked free for that part of the heap |
| // which has not been allocated yet (beyond _next_segment). |
| // The range of segments to be marked is given by [beg..end). |
| // "Allocated" space in this context means there exists a |
| // HeapBlock or a FreeBlock describing this space. |
| // This method takes segment map indices as range boundaries |
| void CodeHeap::mark_segmap_as_free(size_t beg, size_t end) { |
| assert( beg < _number_of_committed_segments, "interval begin out of bounds"); |
| assert(beg < end && end <= _number_of_committed_segments, "interval end out of bounds"); |
| // Don't do unpredictable things in PRODUCT build |
| if (beg < end) { |
| // setup _segmap pointers for faster indexing |
| address p = (address)_segmap.low() + beg; |
| address q = (address)_segmap.low() + end; |
| // initialize interval |
| memset(p, free_sentinel, q-p); |
| } |
| } |
| |
| // Don't get confused here. |
| // All existing blocks, no matter if they are used() or free(), |
| // have their segmap marked as used. This allows to find the |
| // block header (HeapBlock or FreeBlock) for any pointer |
| // within the allocated range (upper limit: _next_segment). |
| // This method takes segment map indices as range boundaries. |
| // The range of segments to be marked is given by [beg..end). |
| void CodeHeap::mark_segmap_as_used(size_t beg, size_t end, bool is_FreeBlock_join) { |
| assert( beg < _number_of_committed_segments, "interval begin out of bounds"); |
| assert(beg < end && end <= _number_of_committed_segments, "interval end out of bounds"); |
| // Don't do unpredictable things in PRODUCT build |
| if (beg < end) { |
| // setup _segmap pointers for faster indexing |
| address p = (address)_segmap.low() + beg; |
| address q = (address)_segmap.low() + end; |
| // initialize interval |
| // If we are joining two free blocks, the segmap range for each |
| // block is consistent. To create a consistent segmap range for |
| // the blocks combined, we have three choices: |
| // 1 - Do a full init from beg to end. Not very efficient because |
| // the segmap range for the left block is potentially initialized |
| // over and over again. |
| // 2 - Carry over the last segmap element value of the left block |
| // and initialize the segmap range of the right block starting |
| // with that value. Saves initializing the left block's segmap |
| // over and over again. Very efficient if FreeBlocks mostly |
| // are appended to the right. |
| // 3 - Take full advantage of the segmap being almost correct with |
| // the two blocks combined. Lets assume the left block consists |
| // of m segments. The the segmap looks like |
| // ... (m-2) (m-1) (m) 0 1 2 3 ... |
| // By substituting the '0' by '1', we create a valid, but |
| // suboptimal, segmap range covering the two blocks combined. |
| // We introduced an extra hop for the find_block_for() iteration. |
| // |
| // When this method is called with is_FreeBlock_join == true, the |
| // segmap index beg must select the first segment of the right block. |
| // Otherwise, it has to select the first segment of the left block. |
| // Variant 3 is used for all FreeBlock joins. |
| if (is_FreeBlock_join && (beg > 0)) { |
| #ifndef PRODUCT |
| FreeBlock* pBlock = (FreeBlock*)block_at(beg); |
| assert(beg + pBlock->length() == end, "Internal error: (%d - %d) != %d", (unsigned int)end, (unsigned int)beg, (unsigned int)(pBlock->length())); |
| assert(*p == 0, "Begin index does not select a block start segment, *p = %2.2x", *p); |
| #endif |
| // If possible, extend the previous hop. |
| if (*(p-1) < (free_sentinel-1)) { |
| *p = *(p-1) + 1; |
| } else { |
| *p = 1; |
| } |
| if (_fragmentation_count++ >= fragmentation_limit) { |
| defrag_segmap(true); |
| _fragmentation_count = 0; |
| } |
| } else { |
| size_t n_bulk = free_sentinel-1; // bulk processing uses template indices [1..254]. |
| // Use shortcut for blocks <= 255 segments. |
| // Special case bulk processing: [0..254]. |
| if ((end - beg) <= n_bulk) { |
| memcpy(p, &segmap_template[0], end - beg); |
| } else { |
| *p++ = 0; // block header marker |
| while (p < q) { |
| if ((p+n_bulk) <= q) { |
| memcpy(p, &segmap_template[1], n_bulk); |
| p += n_bulk; |
| } else { |
| memcpy(p, &segmap_template[1], q-p); |
| p = q; |
| } |
| } |
| } |
| } |
| } |
| } |
| |
| void CodeHeap::invalidate(size_t beg, size_t end, size_t hdr_size) { |
| #ifndef PRODUCT |
| // Fill the given range with some bad value. |
| // length is expected to be in segment_size units. |
| // This prevents inadvertent execution of code leftover from previous use. |
| char* p = low_boundary() + segments_to_size(beg) + hdr_size; |
| memset(p, badCodeHeapNewVal, segments_to_size(end-beg)-hdr_size); |
| #endif |
| } |
| |
| void CodeHeap::clear(size_t beg, size_t end) { |
| mark_segmap_as_free(beg, end); |
| invalidate(beg, end, 0); |
| } |
| |
| void CodeHeap::clear() { |
| _next_segment = 0; |
| clear(_next_segment, _number_of_committed_segments); |
| } |
| |
| |
| static size_t align_to_page_size(size_t size) { |
| const size_t alignment = (size_t)os::vm_page_size(); |
| assert(is_power_of_2(alignment), "no kidding ???"); |
| return (size + alignment - 1) & ~(alignment - 1); |
| } |
| |
| |
| void CodeHeap::on_code_mapping(char* base, size_t size) { |
| #ifdef LINUX |
| extern void linux_wrap_code(char* base, size_t size); |
| linux_wrap_code(base, size); |
| #endif |
| } |
| |
| |
| bool CodeHeap::reserve(ReservedSpace rs, size_t committed_size, size_t segment_size) { |
| assert(rs.size() >= committed_size, "reserved < committed"); |
| assert(segment_size >= sizeof(FreeBlock), "segment size is too small"); |
| assert(is_power_of_2(segment_size), "segment_size must be a power of 2"); |
| assert_locked_or_safepoint(CodeCache_lock); |
| |
| _segment_size = segment_size; |
| _log2_segment_size = exact_log2(segment_size); |
| |
| // Reserve and initialize space for _memory. |
| size_t page_size = os::vm_page_size(); |
| if (os::can_execute_large_page_memory()) { |
| const size_t min_pages = 8; |
| page_size = MIN2(os::page_size_for_region_aligned(committed_size, min_pages), |
| os::page_size_for_region_aligned(rs.size(), min_pages)); |
| } |
| |
| const size_t granularity = os::vm_allocation_granularity(); |
| const size_t c_size = align_up(committed_size, page_size); |
| |
| os::trace_page_sizes(_name, committed_size, rs.size(), page_size, |
| rs.base(), rs.size()); |
| if (!_memory.initialize(rs, c_size)) { |
| return false; |
| } |
| |
| on_code_mapping(_memory.low(), _memory.committed_size()); |
| _number_of_committed_segments = size_to_segments(_memory.committed_size()); |
| _number_of_reserved_segments = size_to_segments(_memory.reserved_size()); |
| assert(_number_of_reserved_segments >= _number_of_committed_segments, "just checking"); |
| const size_t reserved_segments_alignment = MAX2((size_t)os::vm_page_size(), granularity); |
| const size_t reserved_segments_size = align_up(_number_of_reserved_segments, reserved_segments_alignment); |
| const size_t committed_segments_size = align_to_page_size(_number_of_committed_segments); |
| |
| // reserve space for _segmap |
| if (!_segmap.initialize(reserved_segments_size, committed_segments_size)) { |
| return false; |
| } |
| |
| MemTracker::record_virtual_memory_type((address)_segmap.low_boundary(), mtCode); |
| |
| assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "could not commit enough space for segment map"); |
| assert(_segmap.reserved_size() >= (size_t) _number_of_reserved_segments , "could not reserve enough space for segment map"); |
| assert(_segmap.reserved_size() >= _segmap.committed_size() , "just checking"); |
| |
| // initialize remaining instance variables, heap memory and segmap |
| clear(); |
| init_segmap_template(); |
| return true; |
| } |
| |
| |
| bool CodeHeap::expand_by(size_t size) { |
| assert_locked_or_safepoint(CodeCache_lock); |
| |
| // expand _memory space |
| size_t dm = align_to_page_size(_memory.committed_size() + size) - _memory.committed_size(); |
| if (dm > 0) { |
| // Use at least the available uncommitted space if 'size' is larger |
| if (_memory.uncommitted_size() != 0 && dm > _memory.uncommitted_size()) { |
| dm = _memory.uncommitted_size(); |
| } |
| char* base = _memory.low() + _memory.committed_size(); |
| if (!_memory.expand_by(dm)) return false; |
| on_code_mapping(base, dm); |
| size_t i = _number_of_committed_segments; |
| _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)) { |
| return false; |
| } |
| assert(_segmap.committed_size() >= (size_t) _number_of_committed_segments, "just checking"); |
| // initialize additional space (heap memory and segmap) |
| clear(i, _number_of_committed_segments); |
| } |
| return true; |
| } |
| |
| |
| void* CodeHeap::allocate(size_t instance_size) { |
| 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"); |
| assert_locked_or_safepoint(CodeCache_lock); |
| |
| // First check if we can satisfy request from freelist |
| NOT_PRODUCT(verify()); |
| HeapBlock* block = search_freelist(number_of_segments); |
| NOT_PRODUCT(verify()); |
| |
| if (block != NULL) { |
| assert(!block->free(), "must not be marked free"); |
| guarantee((char*) block >= _memory.low_boundary() && (char*) block < _memory.high(), |
| "The newly allocated block " INTPTR_FORMAT " is not within the heap " |
| "starting with " INTPTR_FORMAT " and ending with " INTPTR_FORMAT, |
| p2i(block), p2i(_memory.low_boundary()), p2i(_memory.high())); |
| _max_allocated_capacity = MAX2(_max_allocated_capacity, allocated_capacity()); |
| _blob_count++; |
| return block->allocated_space(); |
| } |
| |
| // Ensure minimum size for allocation to the heap. |
| number_of_segments = MAX2((int)CodeCacheMinBlockLength, (int)number_of_segments); |
| |
| if (_next_segment + number_of_segments <= _number_of_committed_segments) { |
| mark_segmap_as_used(_next_segment, _next_segment + number_of_segments, false); |
| block = block_at(_next_segment); |
| block->initialize(number_of_segments); |
| _next_segment += number_of_segments; |
| guarantee((char*) block >= _memory.low_boundary() && (char*) block < _memory.high(), |
| "The newly allocated block " INTPTR_FORMAT " is not within the heap " |
| "starting with " INTPTR_FORMAT " and ending with " INTPTR_FORMAT, |
| p2i(block), p2i(_memory.low_boundary()), p2i(_memory.high())); |
| _max_allocated_capacity = MAX2(_max_allocated_capacity, allocated_capacity()); |
| _blob_count++; |
| return block->allocated_space(); |
| } else { |
| return NULL; |
| } |
| } |
| |
| // Split the given block into two at the given segment. |
| // This is helpful when a block was allocated too large |
| // to trim off the unused space at the end (interpreter). |
| // It also helps with splitting a large free block during allocation. |
| // Usage state (used or free) must be set by caller since |
| // we don't know if the resulting blocks will be used or free. |
| // split_at is the segment number (relative to segment_for(b)) |
| // where the split happens. The segment with relative |
| // number split_at is the first segment of the split-off block. |
| HeapBlock* CodeHeap::split_block(HeapBlock *b, size_t split_at) { |
| if (b == NULL) return NULL; |
| // After the split, both blocks must have a size of at least CodeCacheMinBlockLength |
| assert((split_at >= CodeCacheMinBlockLength) && (split_at + CodeCacheMinBlockLength <= b->length()), |
| "split position(%d) out of range [0..%d]", (int)split_at, (int)b->length()); |
| size_t split_segment = segment_for(b) + split_at; |
| size_t b_size = b->length(); |
| size_t newb_size = b_size - split_at; |
| |
| HeapBlock* newb = block_at(split_segment); |
| newb->set_length(newb_size); |
| mark_segmap_as_used(segment_for(newb), segment_for(newb) + newb_size, false); |
| b->set_length(split_at); |
| return newb; |
| } |
| |
| void CodeHeap::deallocate_tail(void* p, size_t used_size) { |
| assert(p == find_start(p), "illegal deallocation"); |
| assert_locked_or_safepoint(CodeCache_lock); |
| |
| // Find start of HeapBlock |
| HeapBlock* b = (((HeapBlock *)p) - 1); |
| assert(b->allocated_space() == p, "sanity check"); |
| |
| size_t actual_number_of_segments = b->length(); |
| size_t used_number_of_segments = size_to_segments(used_size + header_size()); |
| size_t unused_number_of_segments = actual_number_of_segments - used_number_of_segments; |
| guarantee(used_number_of_segments <= actual_number_of_segments, "Must be!"); |
| |
| HeapBlock* f = split_block(b, used_number_of_segments); |
| add_to_freelist(f); |
| NOT_PRODUCT(verify()); |
| } |
| |
| void CodeHeap::deallocate(void* p) { |
| assert(p == find_start(p), "illegal deallocation"); |
| assert_locked_or_safepoint(CodeCache_lock); |
| |
| // Find start of HeapBlock |
| HeapBlock* b = (((HeapBlock *)p) - 1); |
| assert(b->allocated_space() == p, "sanity check"); |
| guarantee((char*) b >= _memory.low_boundary() && (char*) b < _memory.high(), |
| "The block to be deallocated " INTPTR_FORMAT " is not within the heap " |
| "starting with " INTPTR_FORMAT " and ending with " INTPTR_FORMAT, |
| p2i(b), p2i(_memory.low_boundary()), p2i(_memory.high())); |
| add_to_freelist(b); |
| NOT_PRODUCT(verify()); |
| } |
| |
| /** |
| * The segment map is used to quickly find the the start (header) of a |
| * code block (e.g. nmethod) when only a pointer to a location inside the |
| * code block is known. This works as follows: |
| * - The storage reserved for the code heap is divided into 'segments'. |
| * - The size of a segment is determined by -XX:CodeCacheSegmentSize=<#bytes>. |
| * - The size must be a power of two to allow the use of shift operations |
| * to quickly convert between segment index and segment address. |
| * - Segment start addresses should be aligned to be multiples of CodeCacheSegmentSize. |
| * - It seems beneficial for CodeCacheSegmentSize to be equal to os::page_size(). |
| * - Allocation in the code cache can only happen at segment start addresses. |
| * - Allocation in the code cache is in units of CodeCacheSegmentSize. |
| * - A pointer in the code cache can be mapped to a segment by calling |
| * segment_for(addr). |
| * - The segment map is a byte array where array element [i] is related |
| * to the i-th segment in the code heap. |
| * - Each time memory is allocated/deallocated from the code cache, |
| * the segment map is updated accordingly. |
| * Note: deallocation does not cause the memory to become "free", as |
| * indicated by the segment map state "free_sentinel". Deallocation |
| * just changes the block state from "used" to "free". |
| * - Elements of the segment map (byte) array are interpreted |
| * as unsigned integer. |
| * - Element values normally identify an offset backwards (in segment |
| * size units) from the associated segment towards the start of |
| * the block. |
| * - Some values have a special meaning: |
| * 0 - This segment is the start of a block (HeapBlock or FreeBlock). |
| * 255 - The free_sentinel value. This is a free segment, i.e. it is |
| * not yet allocated and thus does not belong to any block. |
| * - The value of the current element has to be subtracted from the |
| * current index to get closer to the start. |
| * - If the value of the then current element is zero, the block start |
| * segment is found and iteration stops. Otherwise, start over with the |
| * previous step. |
| * |
| * The following example illustrates a possible 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-1 | nm 1 | -> | m-1 | |
| * seg m | nm 2 | -> | 0 | |
| * seg m+1 | nm 2 | -> | 1 | |
| * ... | nm 2 | -> | 2 | |
| * ... | nm 2 | -> | .. | |
| * ... | nm 2 | -> | 0xFE | (free_sentinel-1) |
| * ... | nm 2 | -> | 1 | |
| * seg m+n | nm 2 | -> | 2 | |
| * ... | nm 2 | -> | | |
| * |
| * How to read: |
| * A value of '0' in the segmap indicates that this segment contains the |
| * beginning of a CodeHeap block. Let's walk through a simple example: |
| * |
| * We want to find the start of the block that contains nm 1, and we are |
| * given a pointer that points into segment m-2. We then read the value |
| * of segmap[m-2]. The value is an offset that points to the segment |
| * which contains the start of the block. |
| * |
| * Another example: We want to locate the start of nm 2, and we happen to |
| * get a pointer that points into seg m+n. We first read seg[n+m], which |
| * returns '2'. So we have to update our segment map index (ix -= segmap[n+m]) |
| * and start over. |
| */ |
| |
| // Find block which contains the passed pointer, |
| // regardless of the block being used or free. |
| // NULL is returned if anything invalid is detected. |
| void* CodeHeap::find_block_for(void* p) const { |
| // Check the pointer to be in committed range. |
| if (!contains(p)) { |
| return NULL; |
| } |
| |
| address seg_map = (address)_segmap.low(); |
| size_t seg_idx = segment_for(p); |
| |
| // This may happen in special cases. Just ignore. |
| // Example: PPC ICache stub generation. |
| if (is_segment_unused(seg_map[seg_idx])) { |
| return NULL; |
| } |
| |
| // Iterate the segment map chain to find the start of the block. |
| while (seg_map[seg_idx] > 0) { |
| // Don't check each segment index to refer to a used segment. |
| // This method is called extremely often. Therefore, any checking |
| // has a significant impact on performance. Rely on CodeHeap::verify() |
| // to do the job on request. |
| seg_idx -= (int)seg_map[seg_idx]; |
| } |
| |
| return address_for(seg_idx); |
| } |
| |
| // Find block which contains the passed pointer. |
| // The block must be used, i.e. must not be a FreeBlock. |
| // Return a pointer that points past the block header. |
| void* CodeHeap::find_start(void* p) const { |
| HeapBlock* h = (HeapBlock*)find_block_for(p); |
| return ((h == NULL) || h->free()) ? NULL : h->allocated_space(); |
| } |
| |
| // Find block which contains the passed pointer. |
| // Same as find_start(p), but with additional safety net. |
| CodeBlob* CodeHeap::find_blob_unsafe(void* start) const { |
| CodeBlob* result = (CodeBlob*)CodeHeap::find_start(start); |
| return (result != NULL && result->blob_contains((address)start)) ? result : NULL; |
| } |
| |
| size_t CodeHeap::alignment_unit() const { |
| // this will be a power of two |
| return _segment_size; |
| } |
| |
| |
| size_t CodeHeap::alignment_offset() const { |
| // The lowest address in any allocated block will be |
| // equal to alignment_offset (mod alignment_unit). |
| return sizeof(HeapBlock) & (_segment_size - 1); |
| } |
| |
| // Returns the current block if available and used. |
| // If not, it returns the subsequent block (if available), NULL otherwise. |
| // Free blocks are merged, therefore there is at most one free block |
| // between two used ones. As a result, the subsequent block (if available) is |
| // guaranteed to be used. |
| // The returned pointer points past the block header. |
| void* CodeHeap::next_used(HeapBlock* b) const { |
| 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(); |
| } |
| |
| // Returns the first used HeapBlock |
| // The returned pointer points to the block header. |
| HeapBlock* CodeHeap::first_block() const { |
| if (_next_segment > 0) |
| return block_at(0); |
| return NULL; |
| } |
| |
| // The returned pointer points to the block header. |
| HeapBlock* CodeHeap::block_start(void* q) const { |
| HeapBlock* b = (HeapBlock*)find_start(q); |
| if (b == NULL) return NULL; |
| return b - 1; |
| } |
| |
| // Returns the next Heap block. |
| // The returned pointer points to the block header. |
| HeapBlock* CodeHeap::next_block(HeapBlock *b) const { |
| if (b == NULL) return NULL; |
| size_t i = segment_for(b) + b->length(); |
| if (i < _next_segment) |
| return block_at(i); |
| return NULL; |
| } |
| |
| |
| // Returns current capacity |
| size_t CodeHeap::capacity() const { |
| return _memory.committed_size(); |
| } |
| |
| size_t CodeHeap::max_capacity() const { |
| return _memory.reserved_size(); |
| } |
| |
| int CodeHeap::allocated_segments() const { |
| return (int)_next_segment; |
| } |
| |
| size_t CodeHeap::allocated_capacity() const { |
| // size of used heap - size on freelist |
| return segments_to_size(_next_segment - _freelist_segments); |
| } |
| |
| // Returns size of the unallocated heap block |
| size_t CodeHeap::heap_unallocated_capacity() const { |
| // Total number of segments - number currently used |
| return segments_to_size(_number_of_reserved_segments - _next_segment); |
| } |
| |
| // Free list management |
| |
| 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) { |
| assert(a != NULL && b != NULL, "must be real pointers"); |
| |
| // Link b into the list after a |
| b->set_link(a->link()); |
| a->set_link(b); |
| |
| // See if we can merge blocks |
| 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 |
| 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"); |
| |
| // Remember linked (following) block. invalidate should only zap header of this block. |
| size_t follower = segment_for(a->link()); |
| // Merge block a to include the following block. |
| a->set_length(a->length() + a->link()->length()); |
| a->set_link(a->link()->link()); |
| |
| // Update the segment map and invalidate block contents. |
| mark_segmap_as_used(follower, segment_for(a) + a->length(), true); |
| // Block contents has already been invalidated by add_to_freelist. |
| // What's left is the header of the following block which now is |
| // in the middle of the merged block. Just zap one segment. |
| invalidate(follower, follower + 1, 0); |
| |
| _freelist_length--; |
| return true; |
| } |
| return false; |
| } |
| |
| |
| void CodeHeap::add_to_freelist(HeapBlock* a) { |
| FreeBlock* b = (FreeBlock*)a; |
| size_t bseg = segment_for(b); |
| _freelist_length++; |
| |
| _blob_count--; |
| assert(_blob_count >= 0, "sanity"); |
| |
| assert(b != _freelist, "cannot be removed twice"); |
| |
| // Mark as free and update free space count |
| _freelist_segments += b->length(); |
| b->set_free(); |
| invalidate(bseg, bseg + b->length(), sizeof(FreeBlock)); |
| |
| // First element in list? |
| if (_freelist == NULL) { |
| b->set_link(NULL); |
| _freelist = b; |
| return; |
| } |
| |
| // Since the freelist is ordered (smaller addresses -> larger addresses) and the |
| // element we want to insert into the freelist has a smaller address 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 addresses. |
| FreeBlock* prev = _freelist; |
| FreeBlock* cur = _freelist->link(); |
| if ((_freelist_length > freelist_limit) && (_last_insert_point != NULL)) { |
| _last_insert_point = (FreeBlock*)find_block_for(_last_insert_point); |
| if ((_last_insert_point != NULL) && _last_insert_point->free() && (_last_insert_point < b)) { |
| prev = _last_insert_point; |
| cur = prev->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); |
| _last_insert_point = prev; |
| } |
| |
| /** |
| * Search freelist for an entry on the list with the best fit. |
| * @return NULL, if no one was found |
| */ |
| HeapBlock* CodeHeap::search_freelist(size_t length) { |
| FreeBlock* found_block = NULL; |
| FreeBlock* found_prev = NULL; |
| size_t found_length = _next_segment; // max it out to begin with |
| |
| HeapBlock* res = NULL; |
| FreeBlock* prev = NULL; |
| FreeBlock* cur = _freelist; |
| |
| length = length < CodeCacheMinBlockLength ? CodeCacheMinBlockLength : length; |
| |
| // Search for best-fitting block |
| while(cur != NULL) { |
| size_t cur_length = cur->length(); |
| if (cur_length == length) { |
| // We have a perfect fit |
| found_block = cur; |
| found_prev = prev; |
| found_length = cur_length; |
| break; |
| } else if ((cur_length > length) && (cur_length < found_length)) { |
| // This is a new, closer fit. Remember block, its previous element, and its length |
| found_block = cur; |
| found_prev = prev; |
| found_length = cur_length; |
| } |
| // Next element in list |
| prev = cur; |
| cur = cur->link(); |
| } |
| |
| if (found_block == NULL) { |
| // None found |
| return NULL; |
| } |
| |
| // Exact (or at least good enough) fit. Remove from list. |
| // Don't leave anything on the freelist smaller than CodeCacheMinBlockLength. |
| if (found_length - length < CodeCacheMinBlockLength) { |
| _freelist_length--; |
| length = found_length; |
| if (found_prev == NULL) { |
| assert(_freelist == found_block, "sanity check"); |
| _freelist = _freelist->link(); |
| } else { |
| assert((found_prev->link() == found_block), "sanity check"); |
| // Unmap element |
| found_prev->set_link(found_block->link()); |
| } |
| res = (HeapBlock*)found_block; |
| // sizeof(HeapBlock) < sizeof(FreeBlock). |
| // Invalidate the additional space that FreeBlock occupies. |
| // The rest of the block should already be invalidated. |
| // This is necessary due to a dubious assert in nmethod.cpp(PcDescCache::reset_to()). |
| // Can't use invalidate() here because it works on segment_size units (too coarse). |
| DEBUG_ONLY(memset((void*)res->allocated_space(), badCodeHeapNewVal, sizeof(FreeBlock) - sizeof(HeapBlock))); |
| } else { |
| // Truncate the free block and return the truncated part |
| // as new HeapBlock. The remaining free block does not |
| // need to be updated, except for it's length. Truncating |
| // the segment map does not invalidate the leading part. |
| res = split_block(found_block, found_length - length); |
| } |
| |
| res->set_used(); |
| _freelist_segments -= length; |
| return res; |
| } |
| |
| int CodeHeap::defrag_segmap(bool do_defrag) { |
| int extra_hops_used = 0; |
| int extra_hops_free = 0; |
| int blocks_used = 0; |
| int blocks_free = 0; |
| for(HeapBlock* h = first_block(); h != NULL; h = next_block(h)) { |
| size_t beg = segment_for(h); |
| size_t end = segment_for(h) + h->length(); |
| int extra_hops = segmap_hops(beg, end); |
| if (h->free()) { |
| extra_hops_free += extra_hops; |
| blocks_free++; |
| } else { |
| extra_hops_used += extra_hops; |
| blocks_used++; |
| } |
| if (do_defrag && (extra_hops > 0)) { |
| mark_segmap_as_used(beg, end, false); |
| } |
| } |
| return extra_hops_used + extra_hops_free; |
| } |
| |
| // Count the hops required to get from the last segment of a |
| // heap block to the block header segment. For the optimal case, |
| // #hops = ((#segments-1)+(free_sentinel-2))/(free_sentinel-1) |
| // The range of segments to be checked is given by [beg..end). |
| // Return the number of extra hops required. There may be extra hops |
| // due to the is_FreeBlock_join optimization in mark_segmap_as_used(). |
| int CodeHeap::segmap_hops(size_t beg, size_t end) { |
| if (beg < end) { |
| // setup _segmap pointers for faster indexing |
| address p = (address)_segmap.low() + beg; |
| int hops_expected = (int)(((end-beg-1)+(free_sentinel-2))/(free_sentinel-1)); |
| int nhops = 0; |
| size_t ix = end-beg-1; |
| while (p[ix] > 0) { |
| ix -= p[ix]; |
| nhops++; |
| } |
| return (nhops > hops_expected) ? nhops - hops_expected : 0; |
| } |
| return 0; |
| } |
| |
| //---------------------------------------------------------------------------- |
| // Non-product code |
| |
| #ifndef PRODUCT |
| |
| void CodeHeap::print() { |
| tty->print_cr("The Heap"); |
| } |
| |
| void CodeHeap::verify() { |
| if (VerifyCodeCache) { |
| assert_locked_or_safepoint(CodeCache_lock); |
| 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"); |
| |
| //---< all free block memory must have been invalidated >--- |
| for(FreeBlock* b = _freelist; b != NULL; b = b->link()) { |
| for (char* c = (char*)b + sizeof(FreeBlock); c < (char*)b + segments_to_size(b->length()); c++) { |
| assert(*c == (char)badCodeHeapNewVal, "FreeBlock@" PTR_FORMAT "(" PTR_FORMAT ") not invalidated @byte %d", p2i(b), b->length(), (int)(c - (char*)b)); |
| } |
| } |
| |
| address seg_map = (address)_segmap.low(); |
| size_t nseg = 0; |
| int extra_hops = 0; |
| count = 0; |
| for(HeapBlock* b = first_block(); b != NULL; b = next_block(b)) { |
| size_t seg1 = segment_for(b); |
| size_t segn = seg1 + b->length(); |
| extra_hops += segmap_hops(seg1, segn); |
| count++; |
| for (size_t i = seg1; i < segn; i++) { |
| nseg++; |
| //---< Verify segment map marking >--- |
| // All allocated segments, no matter if in a free or used block, |
| // must be marked "in use". |
| assert(!is_segment_unused(seg_map[i]), "CodeHeap: unused segment. seg_map[%d]([%d..%d]) = %d, %s block", (int)i, (int)seg1, (int)segn, seg_map[i], b->free()? "free":"used"); |
| assert((unsigned char)seg_map[i] < free_sentinel, "CodeHeap: seg_map[%d]([%d..%d]) = %d (out of range)", (int)i, (int)seg1, (int)segn, seg_map[i]); |
| } |
| } |
| assert(nseg == _next_segment, "CodeHeap: segment count mismatch. found %d, expected %d.", (int)nseg, (int)_next_segment); |
| assert(extra_hops <= _fragmentation_count, "CodeHeap: extra hops wrong. fragmentation: %d, extra hops: %d.", _fragmentation_count, extra_hops); |
| if (extra_hops >= (16 + 2 * count)) { |
| warning("CodeHeap: many extra hops due to optimization. blocks: %d, extra hops: %d.", count, extra_hops); |
| } |
| |
| // 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; |
| } |
| } |
| } |
| |
| #endif |