mfbt/TaggedAnonymousMemory.h
author Jed Davis <jld@mozilla.com>
Tue, 17 Jun 2014 17:54:00 +0200
changeset 211226 7958c801c56ae9b74aac24d854b6cc37a28376ad
child 508163 6f3709b3878117466168c40affa7bca0b60cf75b
permissions -rw-r--r--
Bug 1011350 - Add mfbt support for PR_SET_VMA_ANON_NAME. r=njn r=froydnj This is a Linux kernel feature present in newer Android and B2G devices which allows attaching an arbitrary name to an anonymous memory regions, thus tagging it for the purposes of procfs mapping lists and causing it to be reported separately from adjacent regions with different names.

/* -*- 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/. */

// Some Linux kernels -- specifically, newer versions of Android and
// some B2G devices -- have a feature for assigning names to ranges of
// anonymous memory (i.e., memory that doesn't have a "name" in the
// form of an underlying mapped file).  These names are reported in
// /proc/<pid>/smaps alongside system-level memory usage information
// such as Proportional Set Size (memory usage adjusted for sharing
// between processes), which allows reporting this information at a
// finer granularity than would otherwise be possible (e.g.,
// separating malloc() heap from JS heap).
//
// Existing memory can be tagged with MozTagAnonymousMemory(); it will
// tag the range of complete pages containing the given interval, so
// the results may be inexact if the range isn't page-aligned.
// MozTaggedAnonymousMmap() can be used like mmap() with an extra
// parameter, and will tag the returned memory if the mapping was
// successful (and if it was in fact anonymous).
//
// NOTE: The pointer given as the "tag" argument MUST remain valid as
// long as the mapping exists.  The referenced string is read when
// /proc/<pid>/smaps or /proc/<pid>/maps is read, not when the tag is
// established, so freeing it or changing its contents will have
// unexpected results.  Using a static string is probably best.
//
// Also note that this header can be used by both C and C++ code.

#ifndef mozilla_TaggedAnonymousMemory_h
#define mozilla_TaggedAnonymousMemory_h

#ifndef XP_WIN

#include <sys/types.h>
#include <sys/mman.h>

#include "mozilla/Types.h"

#ifdef ANDROID

#ifdef __cplusplus
extern "C" {
#endif

MFBT_API void
MozTagAnonymousMemory(const void* aPtr, size_t aLength, const char* aTag);

MFBT_API void*
MozTaggedAnonymousMmap(void* aAddr, size_t aLength, int aProt, int aFlags,
                         int aFd, off_t aOffset, const char* aTag);

MFBT_API int
MozTaggedMemoryIsSupported(void);

#ifdef __cplusplus
} // extern "C"
#endif

#else // ANDROID

static inline void
MozTagAnonymousMemory(const void* aPtr, size_t aLength, const char* aTag)
{
}

static inline void*
MozTaggedAnonymousMmap(void* aAddr, size_t aLength, int aProt, int aFlags,
                       int aFd, off_t aOffset, const char* aTag)
{
  return mmap(aAddr, aLength, aProt, aFlags, aFd, aOffset);
}

static inline int
MozTaggedMemoryIsSupported(void)
{
  return 0;
}

#endif // ANDROID

#endif // !XP_WIN

#endif // mozilla_TaggedAnonymousMemory_h