blob: 8bcddb7af61f5209a1eb0d2d5425a45cadada5bc [file] [log] [blame]
// Copyright (c) 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <stddef.h>
#include <stdint.h>
#include "third_party/base/allocator/partition_allocator/partition_alloc_constants.h"
#include "third_party/base/base_export.h"
#include "third_party/base/check.h"
#include "third_party/base/compiler_specific.h"
namespace pdfium {
namespace base {
namespace internal {
struct PartitionPage;
struct PartitionRootBase;
struct PartitionBucket {
// Accessed most in hot path => goes first.
PartitionPage* active_pages_head;
PartitionPage* empty_pages_head;
PartitionPage* decommitted_pages_head;
uint32_t slot_size;
uint32_t num_system_pages_per_slot_span : 8;
uint32_t num_full_pages : 24;
// Public API.
void Init(uint32_t new_slot_size);
// Sets |is_already_zeroed| to true if the allocation was satisfied by
// requesting (a) new page(s) from the operating system, or false otherwise.
// This enables an optimization for when callers use |PartitionAllocZeroFill|:
// there is no need to call memset on fresh pages; the OS has already zeroed
// them. (See |PartitionRootBase::AllocFromBucket|.)
// Note the matching Free() functions are in PartitionPage.
BASE_EXPORT NOINLINE void* SlowPathAlloc(PartitionRootBase* root,
int flags,
size_t size,
bool* is_already_zeroed);
ALWAYS_INLINE bool is_direct_mapped() const {
return !num_system_pages_per_slot_span;
ALWAYS_INLINE size_t get_bytes_per_span() const {
// TODO(ajwong): Change to CheckedMul.
return num_system_pages_per_slot_span * SystemPageSize();
ALWAYS_INLINE uint16_t get_slots_per_span() const {
// TODO(ajwong): Change to CheckedMul.
return static_cast<uint16_t>(get_bytes_per_span() / slot_size);
static ALWAYS_INLINE size_t get_direct_map_size(size_t size) {
// Caller must check that the size is not above the GenericMaxDirectMapped()
// limit before calling. This also guards against integer overflow in the
// calculation here.
DCHECK(size <= GenericMaxDirectMapped());
return (size + SystemPageOffsetMask()) & SystemPageBaseMask();
// TODO(ajwong): Can this be made private?
static PartitionBucket* get_sentinel_bucket();
// This helper function scans a bucket's active page list for a suitable new
// active page. When it finds a suitable new active page (one that has
// free slots and is not empty), it is set as the new active page. If there
// is no suitable new active page, the current active page is set to
// PartitionPage::get_sentinel_page(). As potential pages are scanned, they
// are tidied up according to their state. Empty pages are swept on to the
// empty page list, decommitted pages on to the decommitted page list and full
// pages are unlinked from any list.
// This is where the guts of the bucket maintenance is done!
bool SetNewActivePage();
static void OutOfMemory(const PartitionRootBase* root);
static void OutOfMemoryWithLotsOfUncommitedPages();
static NOINLINE void OnFull();
// Returns a natural number of PartitionPages (calculated by
// get_system_pages_per_slot_span()) to allocate from the current
// SuperPage when the bucket runs out of slots.
ALWAYS_INLINE uint16_t get_pages_per_slot_span();
// Returns the number of system pages in a slot span.
// The calculation attemps to find the best number of System Pages to
// allocate for the given slot_size to minimize wasted space. It uses a
// heuristic that looks at number of bytes wasted after the last slot and
// attempts to account for the PTE usage of each System Page.
uint8_t get_system_pages_per_slot_span();
// Allocates a new slot span with size |num_partition_pages| from the
// current extent. Metadata within this slot span will be uninitialized.
// Returns nullptr on error.
ALWAYS_INLINE void* AllocNewSlotSpan(PartitionRootBase* root,
int flags,
uint16_t num_partition_pages);
// Each bucket allocates a slot span when it runs out of slots.
// A slot span's size is equal to get_pages_per_slot_span() number of
// PartitionPages. This function initializes all PartitionPage within the
// span to point to the first PartitionPage which holds all the metadata
// for the span and registers this bucket as the owner of the span. It does
// NOT put the slots into the bucket's freelist.
ALWAYS_INLINE void InitializeSlotSpan(PartitionPage* page);
// Allocates one slot from the given |page| and then adds the remainder to
// the current bucket. If the |page| was freshly allocated, it must have been
// passed through InitializeSlotSpan() first.
ALWAYS_INLINE char* AllocAndFillFreelist(PartitionPage* page);
static PartitionBucket sentinel_bucket_;
} // namespace internal
} // namespace base
} // namespace pdfium