1 files changed, 165 insertions, 0 deletions
diff --git a/third_party/base/allocator/partition_allocator/partition_page.cc b/third_party/base/allocator/partition_allocator/partition_page.cc
new file mode 100644
index 0000000000..3f70048269
--- /dev/null
+++ b/third_party/base/allocator/partition_allocator/partition_page.cc
@@ -0,0 +1,165 @@
+// 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 "third_party/base/allocator/partition_allocator/partition_page.h"
+
+#include "third_party/base/allocator/partition_allocator/partition_direct_map_extent.h"
+#include "third_party/base/allocator/partition_allocator/partition_root_base.h"
+
+namespace pdfium {
+namespace base {
+namespace internal {
+
+namespace {
+
+ALWAYS_INLINE void PartitionDirectUnmap(PartitionPage* page) {
+  PartitionRootBase* root = PartitionRootBase::FromPage(page);
+  const PartitionDirectMapExtent* extent =
+      PartitionDirectMapExtent::FromPage(page);
+  size_t unmap_size = extent->map_size;
+
+  // Maintain the doubly-linked list of all direct mappings.
+  if (extent->prev_extent) {
+    DCHECK(extent->prev_extent->next_extent == extent);
+    extent->prev_extent->next_extent = extent->next_extent;
+  } else {
+    root->direct_map_list = extent->next_extent;
+  }
+  if (extent->next_extent) {
+    DCHECK(extent->next_extent->prev_extent == extent);
+    extent->next_extent->prev_extent = extent->prev_extent;
+  }
+
+  // Add on the size of the trailing guard page and preceeding partition
+  // page.
+  unmap_size += kPartitionPageSize + kSystemPageSize;
+
+  size_t uncommitted_page_size = page->bucket->slot_size + kSystemPageSize;
+  root->DecreaseCommittedPages(uncommitted_page_size);
+  DCHECK(root->total_size_of_direct_mapped_pages >= uncommitted_page_size);
+  root->total_size_of_direct_mapped_pages -= uncommitted_page_size;
+
+  DCHECK(!(unmap_size & kPageAllocationGranularityOffsetMask));
+
+  char* ptr = reinterpret_cast<char*>(PartitionPage::ToPointer(page));
+  // Account for the mapping starting a partition page before the actual
+  // allocation address.
+  ptr -= kPartitionPageSize;
+
+  FreePages(ptr, unmap_size);
+}
+
+ALWAYS_INLINE void PartitionRegisterEmptyPage(PartitionPage* page) {
+  DCHECK(page->is_empty());
+  PartitionRootBase* root = PartitionRootBase::FromPage(page);
+
+  // If the page is already registered as empty, give it another life.
+  if (page->empty_cache_index != -1) {
+    DCHECK(page->empty_cache_index >= 0);
+    DCHECK(static_cast<unsigned>(page->empty_cache_index) < kMaxFreeableSpans);
+    DCHECK(root->global_empty_page_ring[page->empty_cache_index] == page);
+    root->global_empty_page_ring[page->empty_cache_index] = nullptr;
+  }
+
+  int16_t current_index = root->global_empty_page_ring_index;
+  PartitionPage* page_to_decommit = root->global_empty_page_ring[current_index];
+  // The page might well have been re-activated, filled up, etc. before we get
+  // around to looking at it here.
+  if (page_to_decommit)
+    page_to_decommit->DecommitIfPossible(root);
+
+  // We put the empty slot span on our global list of "pages that were once
+  // empty". thus providing it a bit of breathing room to get re-used before
+  // we really free it. This improves performance, particularly on Mac OS X
+  // which has subpar memory management performance.
+  root->global_empty_page_ring[current_index] = page;
+  page->empty_cache_index = current_index;
+  ++current_index;
+  if (current_index == kMaxFreeableSpans)
+    current_index = 0;
+  root->global_empty_page_ring_index = current_index;
+}
+
+}  // namespace
+
+// static
+PartitionPage PartitionPage::sentinel_page_;
+
+PartitionPage* PartitionPage::get_sentinel_page() {
+  return &sentinel_page_;
+}
+
+void PartitionPage::FreeSlowPath() {
+  DCHECK(this != get_sentinel_page());
+  if (LIKELY(this->num_allocated_slots == 0)) {
+    // Page became fully unused.
+    if (UNLIKELY(bucket->is_direct_mapped())) {
+      PartitionDirectUnmap(this);
+      return;
+    }
+    // If it's the current active page, change it. We bounce the page to
+    // the empty list as a force towards defragmentation.
+    if (LIKELY(this == bucket->active_pages_head))
+      bucket->SetNewActivePage();
+    DCHECK(bucket->active_pages_head != this);
+
+    set_raw_size(0);
+    DCHECK(!get_raw_size());
+
+    PartitionRegisterEmptyPage(this);
+  } else {
+    DCHECK(!bucket->is_direct_mapped());
+    // Ensure that the page is full. That's the only valid case if we
+    // arrive here.
+    DCHECK(this->num_allocated_slots < 0);
+    // A transition of num_allocated_slots from 0 to -1 is not legal, and
+    // likely indicates a double-free.
+    CHECK(this->num_allocated_slots != -1);
+    this->num_allocated_slots = -this->num_allocated_slots - 2;
+    DCHECK(this->num_allocated_slots == bucket->get_slots_per_span() - 1);
+    // Fully used page became partially used. It must be put back on the
+    // non-full page list. Also make it the current page to increase the
+    // chances of it being filled up again. The old current page will be
+    // the next page.
+    DCHECK(!this->next_page);
+    if (LIKELY(bucket->active_pages_head != get_sentinel_page()))
+      this->next_page = bucket->active_pages_head;
+    bucket->active_pages_head = this;
+    --bucket->num_full_pages;
+    // Special case: for a partition page with just a single slot, it may
+    // now be empty and we want to run it through the empty logic.
+    if (UNLIKELY(this->num_allocated_slots == 0))
+      FreeSlowPath();
+  }
+}
+
+void PartitionPage::Decommit(PartitionRootBase* root) {
+  DCHECK(is_empty());
+  DCHECK(!bucket->is_direct_mapped());
+  void* addr = PartitionPage::ToPointer(this);
+  root->DecommitSystemPages(addr, bucket->get_bytes_per_span());
+
+  // We actually leave the decommitted page in the active list. We'll sweep
+  // it on to the decommitted page list when we next walk the active page
+  // list.
+  // Pulling this trick enables us to use a singly-linked page list for all
+  // cases, which is critical in keeping the page metadata structure down to
+  // 32 bytes in size.
+  freelist_head = nullptr;
+  num_unprovisioned_slots = 0;
+  DCHECK(is_decommitted());
+}
+
+void PartitionPage::DecommitIfPossible(PartitionRootBase* root) {
+  DCHECK(empty_cache_index >= 0);
+  DCHECK(static_cast<unsigned>(empty_cache_index) < kMaxFreeableSpans);
+  DCHECK(this == root->global_empty_page_ring[empty_cache_index]);
+  empty_cache_index = -1;
+  if (is_empty())
+    Decommit(root);
+}
+
+}  // namespace internal
+}  // namespace base
+}  // namespace pdfium