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 bool VolatileBuffer::Init(size_t aSize, size_t aAlignment) {
  26   MOZ_ASSERT(!mSize && !mBuf, "Init called twice");
  27   MOZ_ASSERT(!(aAlignment % sizeof(void*)),
  28              "Alignment must be multiple of pointer size");
  29
  30   mSize = aSize;
  31
  32   kern_return_t ret = 0;
  33   if (aSize < MIN_VOLATILE_ALLOC_SIZE) {
  34     goto heap_alloc;
  35   }
  36
  37   ret = vm_allocate(mach_task_self(), (vm_address_t*)&mBuf, mSize,
  38                     VM_FLAGS_PURGABLE | VM_FLAGS_ANYWHERE);
  39   if (ret == KERN_SUCCESS) {
  40     return true;
  41   }
  42
  43 heap_alloc:
  44   (void)posix_memalign(&mBuf, aAlignment, aSize);
  45   mHeap = true;
  46   return !!mBuf;
  47 }
  48
  49 VolatileBuffer::~VolatileBuffer() {
  50   MOZ_ASSERT(mLockCount == 0, "Being destroyed with non-zero lock count?");
  51
  52   if (OnHeap()) {
  53     free(mBuf);
  54   } else {
  55     vm_deallocate(mach_task_self(), (vm_address_t)mBuf, mSize);
  56   }
  57 }
  58
  59 bool VolatileBuffer::Lock(void** aBuf) {
  60   MutexAutoLock lock(mMutex);
  61
  62   MOZ_ASSERT(mBuf, "Attempting to lock an uninitialized VolatileBuffer");
  63
  64   *aBuf = mBuf;
  65   if (++mLockCount > 1 || OnHeap()) {
  66     return true;
  67   }
  68
  69   int state = VM_PURGABLE_NONVOLATILE;
  70   kern_return_t ret = vm_purgable_control(mach_task_self(), (vm_address_t)mBuf,
  71                                           VM_PURGABLE_SET_STATE, &state);
  72   return ret == KERN_SUCCESS && !(state & VM_PURGABLE_EMPTY);
  73 }
  74
  75 void VolatileBuffer::Unlock() {
  76   MutexAutoLock lock(mMutex);
  77
  78   MOZ_ASSERT(mLockCount > 0, "VolatileBuffer unlocked too many times!");
  79   if (--mLockCount || OnHeap()) {
  80     return;
  81   }
  82
  83   int state = VM_PURGABLE_VOLATILE | VM_VOLATILE_GROUP_DEFAULT;
  84   DebugOnly<kern_return_t> ret = vm_purgable_control(
  85       mach_task_self(), (vm_address_t)mBuf, VM_PURGABLE_SET_STATE, &state);
  86   MOZ_ASSERT(ret == KERN_SUCCESS, "Failed to set buffer as purgable");
  87 }
  88
  89 bool VolatileBuffer::OnHeap() const { return mHeap; }
  90
  91 size_t VolatileBuffer::HeapSizeOfExcludingThis(
  92     MallocSizeOf aMallocSizeOf) const {
  93   return OnHeap() ? aMallocSizeOf(mBuf) : 0;
  94 }
  95
  96 size_t VolatileBuffer::NonHeapSizeOfExcludingThis() const {
  97   if (OnHeap()) {
  98     return 0;
  99   }
 100
 101   unsigned long pagemask = getpagesize() - 1;
 102   return (mSize + pagemask) & ~pagemask;
 103 }
 104
 105 }  // namespace mozilla