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v8/include/cppgc/internal/write-barrier.h
Omer Katz c174643b08 cppgc: Implement process-global state accessors. 
Process global accessors for total physical size and used size are
needed for blink. These are implemented via an allocation observer that
atomically updates static counters.

The public api only provides getters for the counters. An internal class
is in charge of updating the counters as needed. A similar split is also
applied to IsAnyIncrementalOrConcurrentMarking().

Drive-by: ProcessHeap is merged into cppgc::internal::WriteBarrier.

Bug: chromium:1056170
Change-Id: Iaedebd1ac9d49238ce6bdd52ffa5d1ef4d28203d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2695394
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72832}
2021-02-17 22:37:24 +00:00

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// Copyright 2020 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef INCLUDE_CPPGC_INTERNAL_WRITE_BARRIER_H_
#define INCLUDE_CPPGC_INTERNAL_WRITE_BARRIER_H_
#include "cppgc/heap-state.h"
#include "cppgc/internal/api-constants.h"
#include "cppgc/internal/atomic-entry-flag.h"
#include "cppgc/sentinel-pointer.h"
#include "cppgc/trace-trait.h"
#include "v8config.h" // NOLINT(build/include_directory)
#if defined(CPPGC_CAGED_HEAP)
#include "cppgc/internal/caged-heap-local-data.h"
#endif
namespace cppgc {
class HeapHandle;
namespace internal {
class WriteBarrierTypeForCagedHeapPolicy;
class WriteBarrierTypeForNonCagedHeapPolicy;
class V8_EXPORT WriteBarrier final {
public:
enum class Type : uint8_t {
kNone,
kMarking,
kGenerational,
};
struct Params {
HeapHandle* heap = nullptr;
#if V8_ENABLE_CHECKS
Type type = Type::kNone;
#endif // !V8_ENABLE_CHECKS
#if defined(CPPGC_CAGED_HEAP)
uintptr_t start = 0;
CagedHeapLocalData& caged_heap() const {
return *reinterpret_cast<CagedHeapLocalData*>(start);
}
uintptr_t slot_offset = 0;
uintptr_t value_offset = 0;
#endif // CPPGC_CAGED_HEAP
};
enum class ValueMode {
kValuePresent,
kNoValuePresent,
};
// Returns the required write barrier for a given `slot` and `value`.
static V8_INLINE Type GetWriteBarrierType(const void* slot, const void* value,
Params& params);
// Returns the required write barrier for a given `slot`.
template <typename HeapHandleCallback>
static V8_INLINE Type GetWriteBarrierType(const void* slot, Params& params,
HeapHandleCallback callback);
template <typename HeapHandleCallback>
static V8_INLINE Type GetWriteBarrierTypeForExternallyReferencedObject(
const void* value, Params& params, HeapHandleCallback callback);
static V8_INLINE void DijkstraMarkingBarrier(const Params& params,
const void* object);
static V8_INLINE void DijkstraMarkingBarrierRange(
const Params& params, const void* first_element, size_t element_size,
size_t number_of_elements, TraceCallback trace_callback);
static V8_INLINE void SteeleMarkingBarrier(const Params& params,
const void* object);
#if defined(CPPGC_YOUNG_GENERATION)
static V8_INLINE void GenerationalBarrier(const Params& params,
const void* slot);
#else // !CPPGC_YOUNG_GENERATION
static V8_INLINE void GenerationalBarrier(const Params& params,
const void* slot) {}
#endif // CPPGC_YOUNG_GENERATION
#if V8_ENABLE_CHECKS
static void CheckParams(Type expected_type, const Params& params);
#else // !V8_ENABLE_CHECKS
static void CheckParams(Type expected_type, const Params& params) {}
#endif // !V8_ENABLE_CHECKS
// The IncrementalOrConcurrentUpdater class allows cppgc internal to update
// |incremental_or_concurrent_marking_flag_|.
class IncrementalOrConcurrentMarkingFlagUpdater;
static bool IsAnyIncrementalOrConcurrentMarking() {
return incremental_or_concurrent_marking_flag_.MightBeEntered();
}
private:
WriteBarrier() = delete;
#if defined(CPPGC_CAGED_HEAP)
using WriteBarrierTypePolicy = WriteBarrierTypeForCagedHeapPolicy;
#else // !CPPGC_CAGED_HEAP
using WriteBarrierTypePolicy = WriteBarrierTypeForNonCagedHeapPolicy;
#endif // !CPPGC_CAGED_HEAP
static void DijkstraMarkingBarrierSlow(const void* value);
static void DijkstraMarkingBarrierSlowWithSentinelCheck(const void* value);
static void DijkstraMarkingBarrierRangeSlow(HeapHandle& heap_handle,
const void* first_element,
size_t element_size,
size_t number_of_elements,
TraceCallback trace_callback);
static void SteeleMarkingBarrierSlow(const void* value);
static void SteeleMarkingBarrierSlowWithSentinelCheck(const void* value);
#if defined(CPPGC_YOUNG_GENERATION)
static CagedHeapLocalData& GetLocalData(HeapHandle&);
static void GenerationalBarrierSlow(const CagedHeapLocalData& local_data,
const AgeTable& ageTable,
const void* slot, uintptr_t value_offset);
#endif // CPPGC_YOUNG_GENERATION
static AtomicEntryFlag incremental_or_concurrent_marking_flag_;
};
template <WriteBarrier::Type type>
V8_INLINE WriteBarrier::Type SetAndReturnType(WriteBarrier::Params& params) {
if (type == WriteBarrier::Type::kNone) return WriteBarrier::Type::kNone;
#if V8_ENABLE_CHECKS
params.type = type;
#endif // !V8_ENABLE_CHECKS
return type;
}
#if defined(CPPGC_CAGED_HEAP)
class V8_EXPORT WriteBarrierTypeForCagedHeapPolicy final {
public:
template <WriteBarrier::ValueMode value_mode, typename HeapHandleCallback>
static V8_INLINE WriteBarrier::Type Get(const void* slot, const void* value,
WriteBarrier::Params& params,
HeapHandleCallback callback) {
return ValueModeDispatch<value_mode>::Get(slot, value, params, callback);
}
template <typename HeapHandleCallback>
static V8_INLINE WriteBarrier::Type GetForExternallyReferenced(
const void* value, WriteBarrier::Params& params, HeapHandleCallback) {
if (!TryGetCagedHeap(value, value, params)) {
return WriteBarrier::Type::kNone;
}
if (V8_UNLIKELY(params.caged_heap().is_incremental_marking_in_progress)) {
return SetAndReturnType<WriteBarrier::Type::kMarking>(params);
}
return SetAndReturnType<WriteBarrier::Type::kNone>(params);
}
private:
WriteBarrierTypeForCagedHeapPolicy() = delete;
template <WriteBarrier::ValueMode value_mode>
struct ValueModeDispatch;
static V8_INLINE bool TryGetCagedHeap(const void* slot, const void* value,
WriteBarrier::Params& params) {
params.start = reinterpret_cast<uintptr_t>(value) &
~(api_constants::kCagedHeapReservationAlignment - 1);
const uintptr_t slot_offset =
reinterpret_cast<uintptr_t>(slot) - params.start;
if (slot_offset > api_constants::kCagedHeapReservationSize) {
// Check if slot is on stack or value is sentinel or nullptr. This relies
// on the fact that kSentinelPointer is encoded as 0x1.
return false;
}
return true;
}
// Returns whether marking is in progress. If marking is not in progress
// sets the start of the cage accordingly.
//
// TODO(chromium:1056170): Create fast path on API.
static bool IsMarking(const HeapHandle&, WriteBarrier::Params&);
};
template <>
struct WriteBarrierTypeForCagedHeapPolicy::ValueModeDispatch<
WriteBarrier::ValueMode::kValuePresent> {
template <typename HeapHandleCallback>
static V8_INLINE WriteBarrier::Type Get(const void* slot, const void* value,
WriteBarrier::Params& params,
HeapHandleCallback) {
bool within_cage = TryGetCagedHeap(slot, value, params);
if (!within_cage) {
return WriteBarrier::Type::kNone;
}
if (V8_LIKELY(!params.caged_heap().is_incremental_marking_in_progress)) {
#if defined(CPPGC_YOUNG_GENERATION)
params.heap = reinterpret_cast<HeapHandle*>(params.start);
params.slot_offset = reinterpret_cast<uintptr_t>(slot) - params.start;
params.value_offset = reinterpret_cast<uintptr_t>(value) - params.start;
return SetAndReturnType<WriteBarrier::Type::kGenerational>(params);
#else // !CPPGC_YOUNG_GENERATION
return SetAndReturnType<WriteBarrier::Type::kNone>(params);
#endif // !CPPGC_YOUNG_GENERATION
}
params.heap = reinterpret_cast<HeapHandle*>(params.start);
return SetAndReturnType<WriteBarrier::Type::kMarking>(params);
}
};
template <>
struct WriteBarrierTypeForCagedHeapPolicy::ValueModeDispatch<
WriteBarrier::ValueMode::kNoValuePresent> {
template <typename HeapHandleCallback>
static V8_INLINE WriteBarrier::Type Get(const void* slot, const void*,
WriteBarrier::Params& params,
HeapHandleCallback callback) {
#if defined(CPPGC_YOUNG_GENERATION)
HeapHandle& handle = callback();
if (V8_LIKELY(!IsMarking(handle, params))) {
// params.start is populated by IsMarking().
params.heap = &handle;
params.slot_offset = reinterpret_cast<uintptr_t>(slot) - params.start;
// params.value_offset stays 0.
if (params.slot_offset > api_constants::kCagedHeapReservationSize) {
// Check if slot is on stack.
return SetAndReturnType<WriteBarrier::Type::kNone>(params);
}
return SetAndReturnType<WriteBarrier::Type::kGenerational>(params);
}
#else // !CPPGC_YOUNG_GENERATION
if (V8_LIKELY(!WriteBarrier::IsAnyIncrementalOrConcurrentMarking())) {
return SetAndReturnType<WriteBarrier::Type::kNone>(params);
}
HeapHandle& handle = callback();
if (V8_UNLIKELY(!subtle::HeapState::IsMarking(handle))) {
return SetAndReturnType<WriteBarrier::Type::kNone>(params);
}
#endif // !CPPGC_YOUNG_GENERATION
params.heap = &handle;
return SetAndReturnType<WriteBarrier::Type::kMarking>(params);
}
};
#endif // CPPGC_CAGED_HEAP
class V8_EXPORT WriteBarrierTypeForNonCagedHeapPolicy final {
public:
template <WriteBarrier::ValueMode value_mode, typename HeapHandleCallback>
static V8_INLINE WriteBarrier::Type Get(const void* slot, const void* value,
WriteBarrier::Params& params,
HeapHandleCallback callback) {
return ValueModeDispatch<value_mode>::Get(slot, value, params, callback);
}
template <typename HeapHandleCallback>
static V8_INLINE WriteBarrier::Type GetForExternallyReferenced(
const void* value, WriteBarrier::Params& params,
HeapHandleCallback callback) {
// The slot will never be used in `Get()` below.
return Get<WriteBarrier::ValueMode::kValuePresent>(nullptr, value, params,
callback);
}
private:
template <WriteBarrier::ValueMode value_mode>
struct ValueModeDispatch;
// TODO(chromium:1056170): Create fast path on API.
static bool IsMarking(const void*, HeapHandle**);
// TODO(chromium:1056170): Create fast path on API.
static bool IsMarking(HeapHandle&);
WriteBarrierTypeForNonCagedHeapPolicy() = delete;
};
template <>
struct WriteBarrierTypeForNonCagedHeapPolicy::ValueModeDispatch<
WriteBarrier::ValueMode::kValuePresent> {
template <typename HeapHandleCallback>
static V8_INLINE WriteBarrier::Type Get(const void*, const void* object,
WriteBarrier::Params& params,
HeapHandleCallback callback) {
// The following check covers nullptr as well as sentinel pointer.
if (object <= static_cast<void*>(kSentinelPointer)) {
return WriteBarrier::Type::kNone;
}
if (IsMarking(object, &params.heap)) {
return SetAndReturnType<WriteBarrier::Type::kMarking>(params);
}
return SetAndReturnType<WriteBarrier::Type::kNone>(params);
}
};
template <>
struct WriteBarrierTypeForNonCagedHeapPolicy::ValueModeDispatch<
WriteBarrier::ValueMode::kNoValuePresent> {
template <typename HeapHandleCallback>
static V8_INLINE WriteBarrier::Type Get(const void*, const void*,
WriteBarrier::Params& params,
HeapHandleCallback callback) {
if (V8_UNLIKELY(WriteBarrier::IsAnyIncrementalOrConcurrentMarking())) {
HeapHandle& handle = callback();
if (IsMarking(handle)) {
params.heap = &handle;
return SetAndReturnType<WriteBarrier::Type::kMarking>(params);
}
}
return WriteBarrier::Type::kNone;
}
};
// static
WriteBarrier::Type WriteBarrier::GetWriteBarrierType(
const void* slot, const void* value, WriteBarrier::Params& params) {
return WriteBarrierTypePolicy::Get<ValueMode::kValuePresent>(slot, value,
params, []() {});
}
// static
template <typename HeapHandleCallback>
WriteBarrier::Type WriteBarrier::GetWriteBarrierType(
const void* slot, WriteBarrier::Params& params,
HeapHandleCallback callback) {
return WriteBarrierTypePolicy::Get<ValueMode::kNoValuePresent>(
slot, nullptr, params, callback);
}
// static
template <typename HeapHandleCallback>
WriteBarrier::Type
WriteBarrier::GetWriteBarrierTypeForExternallyReferencedObject(
const void* value, Params& params, HeapHandleCallback callback) {
return WriteBarrierTypePolicy::GetForExternallyReferenced(value, params,
callback);
}
// static
void WriteBarrier::DijkstraMarkingBarrier(const Params& params,
const void* object) {
CheckParams(Type::kMarking, params);
#if defined(CPPGC_CAGED_HEAP)
// Caged heap already filters out sentinels.
DijkstraMarkingBarrierSlow(object);
#else // !CPPGC_CAGED_HEAP
DijkstraMarkingBarrierSlowWithSentinelCheck(object);
#endif // !CPPGC_CAGED_HEAP
}
// static
void WriteBarrier::DijkstraMarkingBarrierRange(const Params& params,
const void* first_element,
size_t element_size,
size_t number_of_elements,
TraceCallback trace_callback) {
CheckParams(Type::kMarking, params);
DijkstraMarkingBarrierRangeSlow(*params.heap, first_element, element_size,
number_of_elements, trace_callback);
}
// static
void WriteBarrier::SteeleMarkingBarrier(const Params& params,
const void* object) {
CheckParams(Type::kMarking, params);
#if defined(CPPGC_CAGED_HEAP)
// Caged heap already filters out sentinels.
SteeleMarkingBarrierSlow(object);
#else // !CPPGC_CAGED_HEAP
SteeleMarkingBarrierSlowWithSentinelCheck(object);
#endif // !CPPGC_CAGED_HEAP
}
#if defined(CPPGC_YOUNG_GENERATION)
// static
void WriteBarrier::GenerationalBarrier(const Params& params, const void* slot) {
CheckParams(Type::kGenerational, params);
const CagedHeapLocalData& local_data = params.caged_heap();
const AgeTable& age_table = local_data.age_table;
// Bail out if the slot is in young generation.
if (V8_LIKELY(age_table[params.slot_offset] == AgeTable::Age::kYoung)) return;
GenerationalBarrierSlow(local_data, age_table, slot, params.value_offset);
}
#endif // !CPPGC_YOUNG_GENERATION
} // namespace internal
} // namespace cppgc
#endif // INCLUDE_CPPGC_INTERNAL_WRITE_BARRIER_H_
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