/*
* 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;
_freelist_segments = 0;
_freelist_length = 0;
_max_allocated_capacity = 0;
_blob_count = 0;
_nmethod_count = 0;
_adapter_count = 0;
_full_count = 0;
}
// The segmap is marked free for that part of the heap
// which has not been allocated yet (beyond _next_segment).
// "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
void CodeHeap::mark_segmap_as_used(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
int i = 0;
while (p < q) {
*p++ = i++;
if (i == free_sentinel) i = 1;
}
}
}
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");
_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();
return true;
}
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) {
// 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");
// 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 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()));
// 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()).
DEBUG_ONLY(memset((void*)block->allocated_space(), badCodeHeapNewVal, sizeof(FreeBlock) - sizeof(HeapBlock)));
_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);
HeapBlock* b = block_at(_next_segment);
b->initialize(number_of_segments);
_next_segment += number_of_segments;
guarantee((char*) b >= _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(b), p2i(_memory.low_boundary()), p2i(_memory.high()));
_max_allocated_capacity = MAX2(_max_allocated_capacity, allocated_capacity());
_blob_count++;
return b->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);
b->set_length(split_at);
return newb;
}
void CodeHeap::deallocate_tail(void* p, size_t used_size) {
assert(p == find_start(p), "illegal deallocation");
// 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");
// 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());
}
/**
* 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 seg_map = (address)_segmap.low();
if (is_segment_unused(seg_map[seg_idx])) {
return NULL;
}
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();
}
CodeBlob* CodeHeap::find_blob_unsafe(void* start) const {
CodeBlob* result = (CodeBlob*)CodeHeap::find_start(start);
if (result != NULL && result->blob_contains((address)start)) {
return result;
}
return 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.
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
HeapBlock* CodeHeap::first_block() const {
if (_next_segment > 0)
return block_at(0);
return NULL;
}
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 an offset into one
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");
// 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());
invalidate(beg, beg + a->length(), sizeof(FreeBlock));
_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++;
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();
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
*/
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 = found_block;
} 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;
}
//----------------------------------------------------------------------------
// Non-product code
#ifndef PRODUCT
void CodeHeap::print() {
tty->print_cr("The Heap");
}
void CodeHeap::verify() {
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");
//---< 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));
}
}
// Verify segment map marking.
// All allocated segments, no matter if in a free or used block,
// must be marked "in use".
address seg_map = (address)_segmap.low();
size_t nseg = 0;
for(HeapBlock* b = first_block(); b != NULL; b = next_block(b)) {
size_t seg1 = segment_for(b);
size_t segn = seg1 + b->length();
for (size_t i = seg1; i < segn; i++) {
nseg++;
assert(!is_segment_unused(seg_map[i]), "CodeHeap: unused segment. %d [%d..%d], %s block", (int)i, (int)seg1, (int)segn, b->free()? "free":"used");
}
}
assert(nseg == _next_segment, "CodeHeap: segment count mismatch. found %d, expected %d.", (int)nseg, (int)_next_segment);
// 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