ipc/glue/SharedMemory.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include <math.h>
   8
   9 #include "nsString.h"
  10 #include "nsIMemoryReporter.h"
  11 #include "mozilla/ipc/SharedMemory.h"
  12 #include "mozilla/Atomics.h"
  13
  14 namespace mozilla {
  15 namespace ipc {
  16
  17 static Atomic<size_t> gShmemAllocated;
  18 static Atomic<size_t> gShmemMapped;
  19
  20 class ShmemReporter final : public nsIMemoryReporter {
  21   ~ShmemReporter() = default;
  22
  23  public:
  24   NS_DECL_THREADSAFE_ISUPPORTS
  25
  26   NS_IMETHOD
  27   CollectReports(nsIHandleReportCallback* aHandleReport, nsISupports* aData,
  28                  bool aAnonymize) override {
  29     MOZ_COLLECT_REPORT(
  30         "shmem-allocated", KIND_OTHER, UNITS_BYTES, gShmemAllocated,
  31         "Memory shared with other processes that is accessible (but not "
  32         "necessarily mapped).");
  33
  34     MOZ_COLLECT_REPORT(
  35         "shmem-mapped", KIND_OTHER, UNITS_BYTES, gShmemMapped,
  36         "Memory shared with other processes that is mapped into the address "
  37         "space.");
  38
  39     return NS_OK;
  40   }
  41 };
  42
  43 NS_IMPL_ISUPPORTS(ShmemReporter, nsIMemoryReporter)
  44
  45 SharedMemory::SharedMemory() : mAllocSize(0), mMappedSize(0) {
  46   static Atomic<bool> registered;
  47   if (registered.compareExchange(false, true)) {
  48     RegisterStrongMemoryReporter(new ShmemReporter());
  49   }
  50 }
  51
  52 /*static*/
  53 size_t SharedMemory::PageAlignedSize(size_t aSize) {
  54   size_t pageSize = SystemPageSize();
  55   size_t nPagesNeeded = size_t(ceil(double(aSize) / double(pageSize)));
  56   return pageSize * nPagesNeeded;
  57 }
  58
  59 void SharedMemory::Created(size_t aNBytes) {
  60   mAllocSize = aNBytes;
  61   gShmemAllocated += mAllocSize;
  62 }
  63
  64 void SharedMemory::Mapped(size_t aNBytes) {
  65   mMappedSize = aNBytes;
  66   gShmemMapped += mMappedSize;
  67 }
  68
  69 void SharedMemory::Unmapped() {
  70   MOZ_ASSERT(gShmemMapped >= mMappedSize, "Can't unmap more than mapped");
  71   gShmemMapped -= mMappedSize;
  72   mMappedSize = 0;
  73 }
  74
  75 /*static*/
  76 void SharedMemory::Destroyed() {
  77   MOZ_ASSERT(gShmemAllocated >= mAllocSize,
  78              "Can't destroy more than allocated");
  79   gShmemAllocated -= mAllocSize;
  80   mAllocSize = 0;
  81 }
  82
  83 }  // namespace ipc
  84 }  // namespace mozilla