gecko-dev/ipc/glue/SharedMemory.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include <math.h>

#include "nsString.h"
#include "nsIMemoryReporter.h"
#include "mozilla/ipc/SharedMemory.h"
#include "mozilla/Atomics.h"

namespace mozilla {
namespace ipc {

static Atomic<size_t> gShmemAllocated;
static Atomic<size_t> gShmemMapped;

class ShmemReporter final : public nsIMemoryReporter {
  ~ShmemReporter() = default;

 public:
  NS_DECL_THREADSAFE_ISUPPORTS

  NS_IMETHOD
  CollectReports(nsIHandleReportCallback* aHandleReport, nsISupports* aData,
                 bool aAnonymize) override {
    MOZ_COLLECT_REPORT(
        "shmem-allocated", KIND_OTHER, UNITS_BYTES, gShmemAllocated,
        "Memory shared with other processes that is accessible (but not "
        "necessarily mapped).");

    MOZ_COLLECT_REPORT(
        "shmem-mapped", KIND_OTHER, UNITS_BYTES, gShmemMapped,
        "Memory shared with other processes that is mapped into the address "
        "space.");

    return NS_OK;
  }
};

NS_IMPL_ISUPPORTS(ShmemReporter, nsIMemoryReporter)

SharedMemory::SharedMemory() : mAllocSize(0), mMappedSize(0) {
  static Atomic<bool> registered;
  if (registered.compareExchange(false, true)) {
    RegisterStrongMemoryReporter(new ShmemReporter());
  }
}

/*static*/
size_t SharedMemory::PageAlignedSize(size_t aSize) {
  size_t pageSize = SystemPageSize();
  size_t nPagesNeeded = size_t(ceil(double(aSize) / double(pageSize)));
  return pageSize * nPagesNeeded;
}

void SharedMemory::Created(size_t aNBytes) {
  mAllocSize = aNBytes;
  gShmemAllocated += mAllocSize;
}

void SharedMemory::Mapped(size_t aNBytes) {
  mMappedSize = aNBytes;
  gShmemMapped += mMappedSize;
}

void SharedMemory::Unmapped() {
  MOZ_ASSERT(gShmemMapped >= mMappedSize, "Can't unmap more than mapped");
  gShmemMapped -= mMappedSize;
  mMappedSize = 0;
}

/*static*/
void SharedMemory::Destroyed() {
  MOZ_ASSERT(gShmemAllocated >= mAllocSize,
             "Can't destroy more than allocated");
  gShmemAllocated -= mAllocSize;
  mAllocSize = 0;
}

}  // namespace ipc
}  // namespace mozilla