memory/volatile/VolatileBufferOSX.cpp

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this
   3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #include "VolatileBuffer.h"
   6 #include "mozilla/Assertions.h"
   7 #include "mozilla/DebugOnly.h"
   8 #include "mozilla/mozalloc.h"
   9
  10 #include <mach/mach.h>
  11 #include <sys/mman.h>
  12 #include <unistd.h>
  13
  14 #define MIN_VOLATILE_ALLOC_SIZE 8192
  15
  16 namespace mozilla {
  17
  18 VolatileBuffer::VolatileBuffer()
  19   : mMutex("VolatileBuffer")
  20   , mBuf(nullptr)
  21   , mSize(0)
  22   , mLockCount(0)
  23   , mHeap(false)
  24 {
  25 }
  26
  27 bool
  28 VolatileBuffer::Init(size_t aSize, size_t aAlignment)
  29 {
  30   MOZ_ASSERT(!mSize && !mBuf, "Init called twice");
  31   MOZ_ASSERT(!(aAlignment % sizeof(void *)),
  32              "Alignment must be multiple of pointer size");
  33
  34   mSize = aSize;
  35
  36   kern_return_t ret = 0;
  37   if (aSize < MIN_VOLATILE_ALLOC_SIZE) {
  38     goto heap_alloc;
  39   }
  40
  41   ret = vm_allocate(mach_task_self(),
  42                     (vm_address_t*)&mBuf,
  43                     mSize,
  44                     VM_FLAGS_PURGABLE | VM_FLAGS_ANYWHERE);
  45   if (ret == KERN_SUCCESS) {
  46     return true;
  47   }
  48
  49 heap_alloc:
  50   (void)moz_posix_memalign(&mBuf, aAlignment, aSize);
  51   mHeap = true;
  52   return !!mBuf;
  53 }
  54
  55 VolatileBuffer::~VolatileBuffer()
  56 {
  57   MOZ_ASSERT(mLockCount == 0, "Being destroyed with non-zero lock count?");
  58
  59   if (OnHeap()) {
  60     free(mBuf);
  61   } else {
  62     vm_deallocate(mach_task_self(), (vm_address_t)mBuf, mSize);
  63   }
  64 }
  65
  66 bool
  67 VolatileBuffer::Lock(void** aBuf)
  68 {
  69   MutexAutoLock lock(mMutex);
  70
  71   MOZ_ASSERT(mBuf, "Attempting to lock an uninitialized VolatileBuffer");
  72
  73   *aBuf = mBuf;
  74   if (++mLockCount > 1 || OnHeap()) {
  75     return true;
  76   }
  77
  78   int state = VM_PURGABLE_NONVOLATILE;
  79   kern_return_t ret =
  80     vm_purgable_control(mach_task_self(),
  81                         (vm_address_t)mBuf,
  82                         VM_PURGABLE_SET_STATE,
  83                         &state);
  84   return ret == KERN_SUCCESS && !(state & VM_PURGABLE_EMPTY);
  85 }
  86
  87 void
  88 VolatileBuffer::Unlock()
  89 {
  90   MutexAutoLock lock(mMutex);
  91
  92   MOZ_ASSERT(mLockCount > 0, "VolatileBuffer unlocked too many times!");
  93   if (--mLockCount || OnHeap()) {
  94     return;
  95   }
  96
  97   int state = VM_PURGABLE_VOLATILE | VM_VOLATILE_GROUP_DEFAULT;
  98   DebugOnly<kern_return_t> ret =
  99     vm_purgable_control(mach_task_self(),
 100                         (vm_address_t)mBuf,
 101                         VM_PURGABLE_SET_STATE,
 102                         &state);
 103   MOZ_ASSERT(ret == KERN_SUCCESS, "Failed to set buffer as purgable");
 104 }
 105
 106 bool
 107 VolatileBuffer::OnHeap() const
 108 {
 109   return mHeap;
 110 }
 111
 112 size_t
 113 VolatileBuffer::HeapSizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const
 114 {
 115   return OnHeap() ? aMallocSizeOf(mBuf) : 0;
 116 }
 117
 118 size_t
 119 VolatileBuffer::NonHeapSizeOfExcludingThis() const
 120 {
 121   if (OnHeap()) {
 122     return 0;
 123   }
 124
 125   unsigned long pagemask = getpagesize() - 1;
 126   return (mSize + pagemask) & ~pagemask;
 127 }
 128
 129 } // namespace mozilla