mfbt/TaggedAnonymousMemory.h

   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 // Some Linux kernels -- specifically, newer versions of Android and
   8 // some B2G devices -- have a feature for assigning names to ranges of
   9 // anonymous memory (i.e., memory that doesn't have a "name" in the
  10 // form of an underlying mapped file).  These names are reported in
  11 // /proc/<pid>/smaps alongside system-level memory usage information
  12 // such as Proportional Set Size (memory usage adjusted for sharing
  13 // between processes), which allows reporting this information at a
  14 // finer granularity than would otherwise be possible (e.g.,
  15 // separating malloc() heap from JS heap).
  16 //
  17 // Existing memory can be tagged with MozTagAnonymousMemory(); it will
  18 // tag the range of complete pages containing the given interval, so
  19 // the results may be inexact if the range isn't page-aligned.
  20 // MozTaggedAnonymousMmap() can be used like mmap() with an extra
  21 // parameter, and will tag the returned memory if the mapping was
  22 // successful (and if it was in fact anonymous).
  23 //
  24 // NOTE: The pointer given as the "tag" argument MUST remain valid as
  25 // long as the mapping exists.  The referenced string is read when
  26 // /proc/<pid>/smaps or /proc/<pid>/maps is read, not when the tag is
  27 // established, so freeing it or changing its contents will have
  28 // unexpected results.  Using a static string is probably best.
  29 //
  30 // Also note that this header can be used by both C and C++ code.
  31
  32 #ifndef mozilla_TaggedAnonymousMemory_h
  33 #define mozilla_TaggedAnonymousMemory_h
  34
  35 #ifndef XP_WIN
  36
  37 #  ifdef __wasi__
  38 #    include <stdlib.h>
  39 #  else
  40 #    include <sys/types.h>
  41 #    include <sys/mman.h>
  42 #  endif  // __wasi__
  43
  44 #  include "mozilla/Types.h"
  45
  46 #  ifdef ANDROID
  47
  48 #    ifdef __cplusplus
  49 extern "C" {
  50 #    endif
  51
  52 MFBT_API void MozTagAnonymousMemory(const void* aPtr, size_t aLength,
  53                                     const char* aTag);
  54
  55 MFBT_API void* MozTaggedAnonymousMmap(void* aAddr, size_t aLength, int aProt,
  56                                       int aFlags, int aFd, off_t aOffset,
  57                                       const char* aTag);
  58
  59 MFBT_API int MozTaggedMemoryIsSupported(void);
  60
  61 #    ifdef __cplusplus
  62 }  // extern "C"
  63 #    endif
  64
  65 #  else  // ANDROID
  66
  67 static inline void MozTagAnonymousMemory(const void* aPtr, size_t aLength,
  68                                          const char* aTag) {}
  69
  70 static inline void* MozTaggedAnonymousMmap(void* aAddr, size_t aLength,
  71                                            int aProt, int aFlags, int aFd,
  72                                            off_t aOffset, const char* aTag) {
  73 #    ifdef __wasi__
  74   MOZ_CRASH("We don't use this memory for WASI right now.");
  75   return nullptr;
  76 #    else
  77   return mmap(aAddr, aLength, aProt, aFlags, aFd, aOffset);
  78 #    endif
  79 }
  80
  81 static inline int MozTaggedMemoryIsSupported(void) { return 0; }
  82
  83 #  endif  // ANDROID
  84
  85 #endif  // !XP_WIN
  86
  87 #endif  // mozilla_TaggedAnonymousMemory_h