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/*
* Copyright (C) 2017 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include "Subspace.h"
#include "JSCInlines.h"
#include "MarkedAllocatorInlines.h"
#include "MarkedBlockInlines.h"
#include "PreventCollectionScope.h"
#include "SubspaceInlines.h"
namespace JSC {
namespace {
// Writing it this way ensures that when you pass this as a functor, the callee is specialized for
// this callback. If you wrote this as a normal function then the callee would be specialized for
// the function's type and it would have indirect calls to that function. And unlike a lambda, it's
// possible to mark this ALWAYS_INLINE.
struct DestroyFunc {
ALWAYS_INLINE void operator()(VM& vm, JSCell* cell) const
{
ASSERT(cell->structureID());
ASSERT(cell->inlineTypeFlags() & StructureIsImmortal);
Structure* structure = cell->structure(vm);
const ClassInfo* classInfo = structure->classInfo();
MethodTable::DestroyFunctionPtr destroy = classInfo->methodTable.destroy;
destroy(cell);
}
};
} // anonymous namespace
Subspace::Subspace(CString name, Heap& heap, AllocatorAttributes attributes)
: m_space(heap.objectSpace())
, m_name(name)
, m_attributes(attributes)
{
// It's remotely possible that we're GCing right now even if the client is careful to only
// create subspaces right after VM creation, since collectContinuously (and probably other
// things) could cause a GC to be launched at pretty much any time and it's not 100% obvious
// that all clients would be able to ensure that there are zero safepoints between when they
// create VM and when they do this. Preventing GC while we're creating the Subspace ensures
// that we don't have to worry about whether it's OK for the GC to ever see a brand new
// subspace.
PreventCollectionScope preventCollectionScope(heap);
heap.objectSpace().m_subspaces.append(this);
for (size_t i = MarkedSpace::numSizeClasses; i--;)
m_allocatorForSizeStep[i] = nullptr;
}
Subspace::~Subspace()
{
}
FreeList Subspace::finishSweep(MarkedBlock::Handle& block, MarkedBlock::Handle::SweepMode sweepMode)
{
return block.finishSweepKnowingSubspace(sweepMode, DestroyFunc());
}
void Subspace::destroy(VM& vm, JSCell* cell)
{
DestroyFunc()(vm, cell);
}
// The reason why we distinguish between allocate and tryAllocate is to minimize the number of
// checks on the allocation path in both cases. Likewise, the reason why we have overloads with and
// without deferralContext is to minimize the amount of code for calling allocate when you don't
// need the deferralContext.
void* Subspace::allocate(size_t size)
{
if (MarkedAllocator* allocator = tryAllocatorFor(size))
return allocator->allocate();
return allocateSlow(nullptr, size);
}
void* Subspace::allocate(GCDeferralContext* deferralContext, size_t size)
{
if (MarkedAllocator* allocator = tryAllocatorFor(size))
return allocator->allocate(deferralContext);
return allocateSlow(deferralContext, size);
}
void* Subspace::tryAllocate(size_t size)
{
if (MarkedAllocator* allocator = tryAllocatorFor(size))
return allocator->tryAllocate();
return tryAllocateSlow(nullptr, size);
}
void* Subspace::tryAllocate(GCDeferralContext* deferralContext, size_t size)
{
if (MarkedAllocator* allocator = tryAllocatorFor(size))
return allocator->tryAllocate(deferralContext);
return tryAllocateSlow(deferralContext, size);
}
MarkedAllocator* Subspace::allocatorForSlow(size_t size)
{
size_t index = MarkedSpace::sizeClassToIndex(size);
size_t sizeClass = MarkedSpace::s_sizeClassForSizeStep[index];
if (!sizeClass)
return nullptr;
// This is written in such a way that it's OK for the JIT threads to end up here if they want
// to generate code that uses some allocator that hadn't been used yet. Note that a possibly-
// just-as-good solution would be to return null if we're in the JIT since the JIT treats null
// allocator as "please always take the slow path". But, that could lead to performance
// surprises and the algorithm here is pretty easy. Only this code has to hold the lock, to
// prevent simultaneously MarkedAllocator creations from multiple threads. This code ensures
// that any "forEachAllocator" traversals will only see this allocator after it's initialized
// enough: it will have
auto locker = holdLock(m_space.allocatorLock());
if (MarkedAllocator* allocator = m_allocatorForSizeStep[index])
return allocator;
if (false)
dataLog("Creating marked allocator for ", m_name, ", ", m_attributes, ", ", sizeClass, ".\n");
MarkedAllocator* allocator = m_space.addMarkedAllocator(locker, this, sizeClass);
index = MarkedSpace::sizeClassToIndex(sizeClass);
for (;;) {
if (MarkedSpace::s_sizeClassForSizeStep[index] != sizeClass)
break;
m_allocatorForSizeStep[index] = allocator;
if (!index--)
break;
}
allocator->setNextAllocatorInSubspace(m_firstAllocator);
WTF::storeStoreFence();
m_firstAllocator = allocator;
return allocator;
}
void* Subspace::allocateSlow(GCDeferralContext* deferralContext, size_t size)
{
void* result = tryAllocateSlow(deferralContext, size);
RELEASE_ASSERT(result);
return result;
}
void* Subspace::tryAllocateSlow(GCDeferralContext* deferralContext, size_t size)
{
if (MarkedAllocator* allocator = allocatorFor(size))
return allocator->tryAllocate(deferralContext);
if (size <= Options::largeAllocationCutoff()
&& size <= MarkedSpace::largeCutoff) {
dataLog("FATAL: attampting to allocate small object using large allocation.\n");
dataLog("Requested allocation size: ", size, "\n");
RELEASE_ASSERT_NOT_REACHED();
}
m_space.heap()->collectIfNecessaryOrDefer(deferralContext);
size = WTF::roundUpToMultipleOf<MarkedSpace::sizeStep>(size);
LargeAllocation* allocation = LargeAllocation::tryCreate(*m_space.m_heap, size, this);
if (!allocation)
return nullptr;
m_space.m_largeAllocations.append(allocation);
m_space.m_heap->didAllocate(size);
m_space.m_capacity += size;
m_largeAllocations.append(allocation);
return allocation->cell();
}
} // namespace JSC
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