https://github.com/mozilla/gecko-dev
Tip revision: 46f5468208a4908c41c00558853b9bf36b4dc874 authored by ffxbld on 02 March 2017, 15:17:41 UTC
Added FENNEC_52_0_RELEASE FENNEC_52_0_BUILD1 tag(s) for changeset 8fad70c31a1c. DONTBUILD CLOSED TREE a=release
Added FENNEC_52_0_RELEASE FENNEC_52_0_BUILD1 tag(s) for changeset 8fad70c31a1c. DONTBUILD CLOSED TREE a=release
Tip revision: 46f5468
GCRuntime.h
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* vim: set ts=8 sts=4 et sw=4 tw=99:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef gc_GCRuntime_h
#define gc_GCRuntime_h
#include "mozilla/Atomics.h"
#include "mozilla/EnumSet.h"
#include "jsfriendapi.h"
#include "jsgc.h"
#include "gc/Heap.h"
#include "gc/Nursery.h"
#include "gc/Statistics.h"
#include "gc/StoreBuffer.h"
#include "gc/Tracer.h"
#include "js/GCAnnotations.h"
namespace js {
class AutoLockGC;
class AutoLockHelperThreadState;
class VerifyPreTracer;
namespace gc {
typedef Vector<JS::Zone*, 4, SystemAllocPolicy> ZoneVector;
using BlackGrayEdgeVector = Vector<TenuredCell*, 0, SystemAllocPolicy>;
class AutoMaybeStartBackgroundAllocation;
class MarkingValidator;
class AutoTraceSession;
struct MovingTracer;
class ChunkPool
{
Chunk* head_;
size_t count_;
public:
ChunkPool() : head_(nullptr), count_(0) {}
size_t count() const { return count_; }
Chunk* head() { MOZ_ASSERT(head_); return head_; }
Chunk* pop();
void push(Chunk* chunk);
Chunk* remove(Chunk* chunk);
#ifdef DEBUG
bool contains(Chunk* chunk) const;
bool verify() const;
#endif
// Pool mutation does not invalidate an Iter unless the mutation
// is of the Chunk currently being visited by the Iter.
class Iter {
public:
explicit Iter(ChunkPool& pool) : current_(pool.head_) {}
bool done() const { return !current_; }
void next();
Chunk* get() const { return current_; }
operator Chunk*() const { return get(); }
Chunk* operator->() const { return get(); }
private:
Chunk* current_;
};
};
// Performs extra allocation off the main thread so that when memory is
// required on the main thread it will already be available and waiting.
class BackgroundAllocTask : public GCParallelTask
{
// Guarded by the GC lock.
JSRuntime* runtime;
ChunkPool& chunkPool_;
const bool enabled_;
public:
BackgroundAllocTask(JSRuntime* rt, ChunkPool& pool);
bool enabled() const { return enabled_; }
protected:
void run() override;
};
// Search the provided Chunks for free arenas and decommit them.
class BackgroundDecommitTask : public GCParallelTask
{
public:
using ChunkVector = mozilla::Vector<Chunk*>;
explicit BackgroundDecommitTask(JSRuntime *rt) : runtime(rt) {}
void setChunksToScan(ChunkVector &chunks);
protected:
void run() override;
private:
JSRuntime* runtime;
ChunkVector toDecommit;
};
/*
* Encapsulates all of the GC tunables. These are effectively constant and
* should only be modified by setParameter.
*/
class GCSchedulingTunables
{
/*
* Soft limit on the number of bytes we are allowed to allocate in the GC
* heap. Attempts to allocate gcthings over this limit will return null and
* subsequently invoke the standard OOM machinery, independent of available
* physical memory.
*/
size_t gcMaxBytes_;
/*
* The base value used to compute zone->trigger.gcBytes(). When
* usage.gcBytes() surpasses threshold.gcBytes() for a zone, the zone may
* be scheduled for a GC, depending on the exact circumstances.
*/
size_t gcZoneAllocThresholdBase_;
/* Fraction of threshold.gcBytes() which triggers an incremental GC. */
double zoneAllocThresholdFactor_;
/*
* Number of bytes to allocate between incremental slices in GCs triggered
* by the zone allocation threshold.
*/
size_t zoneAllocDelayBytes_;
/*
* Totally disables |highFrequencyGC|, the HeapGrowthFactor, and other
* tunables that make GC non-deterministic.
*/
bool dynamicHeapGrowthEnabled_;
/*
* We enter high-frequency mode if we GC a twice within this many
* microseconds. This value is stored directly in microseconds.
*/
uint64_t highFrequencyThresholdUsec_;
/*
* When in the |highFrequencyGC| mode, these parameterize the per-zone
* "HeapGrowthFactor" computation.
*/
uint64_t highFrequencyLowLimitBytes_;
uint64_t highFrequencyHighLimitBytes_;
double highFrequencyHeapGrowthMax_;
double highFrequencyHeapGrowthMin_;
/*
* When not in |highFrequencyGC| mode, this is the global (stored per-zone)
* "HeapGrowthFactor".
*/
double lowFrequencyHeapGrowth_;
/*
* Doubles the length of IGC slices when in the |highFrequencyGC| mode.
*/
bool dynamicMarkSliceEnabled_;
/*
* Controls whether painting can trigger IGC slices.
*/
bool refreshFrameSlicesEnabled_;
/*
* Controls the number of empty chunks reserved for future allocation.
*/
uint32_t minEmptyChunkCount_;
uint32_t maxEmptyChunkCount_;
public:
GCSchedulingTunables()
: gcMaxBytes_(0),
gcZoneAllocThresholdBase_(30 * 1024 * 1024),
zoneAllocThresholdFactor_(0.9),
zoneAllocDelayBytes_(1024 * 1024),
dynamicHeapGrowthEnabled_(false),
highFrequencyThresholdUsec_(1000 * 1000),
highFrequencyLowLimitBytes_(100 * 1024 * 1024),
highFrequencyHighLimitBytes_(500 * 1024 * 1024),
highFrequencyHeapGrowthMax_(3.0),
highFrequencyHeapGrowthMin_(1.5),
lowFrequencyHeapGrowth_(1.5),
dynamicMarkSliceEnabled_(false),
refreshFrameSlicesEnabled_(true),
minEmptyChunkCount_(1),
maxEmptyChunkCount_(30)
{}
size_t gcMaxBytes() const { return gcMaxBytes_; }
size_t gcZoneAllocThresholdBase() const { return gcZoneAllocThresholdBase_; }
double zoneAllocThresholdFactor() const { return zoneAllocThresholdFactor_; }
size_t zoneAllocDelayBytes() const { return zoneAllocDelayBytes_; }
bool isDynamicHeapGrowthEnabled() const { return dynamicHeapGrowthEnabled_; }
uint64_t highFrequencyThresholdUsec() const { return highFrequencyThresholdUsec_; }
uint64_t highFrequencyLowLimitBytes() const { return highFrequencyLowLimitBytes_; }
uint64_t highFrequencyHighLimitBytes() const { return highFrequencyHighLimitBytes_; }
double highFrequencyHeapGrowthMax() const { return highFrequencyHeapGrowthMax_; }
double highFrequencyHeapGrowthMin() const { return highFrequencyHeapGrowthMin_; }
double lowFrequencyHeapGrowth() const { return lowFrequencyHeapGrowth_; }
bool isDynamicMarkSliceEnabled() const { return dynamicMarkSliceEnabled_; }
bool areRefreshFrameSlicesEnabled() const { return refreshFrameSlicesEnabled_; }
unsigned minEmptyChunkCount(const AutoLockGC&) const { return minEmptyChunkCount_; }
unsigned maxEmptyChunkCount() const { return maxEmptyChunkCount_; }
MOZ_MUST_USE bool setParameter(JSGCParamKey key, uint32_t value, const AutoLockGC& lock);
};
/*
* GC Scheduling Overview
* ======================
*
* Scheduling GC's in SpiderMonkey/Firefox is tremendously complicated because
* of the large number of subtle, cross-cutting, and widely dispersed factors
* that must be taken into account. A summary of some of the more important
* factors follows.
*
* Cost factors:
*
* * GC too soon and we'll revisit an object graph almost identical to the
* one we just visited; since we are unlikely to find new garbage, the
* traversal will be largely overhead. We rely heavily on external factors
* to signal us that we are likely to find lots of garbage: e.g. "a tab
* just got closed".
*
* * GC too late and we'll run out of memory to allocate (e.g. Out-Of-Memory,
* hereafter simply abbreviated to OOM). If this happens inside
* SpiderMonkey we may be able to recover, but most embedder allocations
* will simply crash on OOM, even if the GC has plenty of free memory it
* could surrender.
*
* * Memory fragmentation: if we fill the process with GC allocations, a
* request for a large block of contiguous memory may fail because no
* contiguous block is free, despite having enough memory available to
* service the request.
*
* * Management overhead: if our GC heap becomes large, we create extra
* overhead when managing the GC's structures, even if the allocations are
* mostly unused.
*
* Heap Management Factors:
*
* * GC memory: The GC has its own allocator that it uses to make fixed size
* allocations for GC managed things. In cases where the GC thing requires
* larger or variable sized memory to implement itself, it is responsible
* for using the system heap.
*
* * C Heap Memory: Rather than allowing for large or variable allocations,
* the SpiderMonkey GC allows GC things to hold pointers to C heap memory.
* It is the responsibility of the thing to free this memory with a custom
* finalizer (with the sole exception of NativeObject, which knows about
* slots and elements for performance reasons). C heap memory has different
* performance and overhead tradeoffs than GC internal memory, which need
* to be considered with scheduling a GC.
*
* Application Factors:
*
* * Most applications allocate heavily at startup, then enter a processing
* stage where memory utilization remains roughly fixed with a slower
* allocation rate. This is not always the case, however, so while we may
* optimize for this pattern, we must be able to handle arbitrary
* allocation patterns.
*
* Other factors:
*
* * Other memory: This is memory allocated outside the purview of the GC.
* Data mapped by the system for code libraries, data allocated by those
* libraries, data in the JSRuntime that is used to manage the engine,
* memory used by the embedding that is not attached to a GC thing, memory
* used by unrelated processes running on the hardware that use space we
* could otherwise use for allocation, etc. While we don't have to manage
* it, we do have to take it into account when scheduling since it affects
* when we will OOM.
*
* * Physical Reality: All real machines have limits on the number of bits
* that they are physically able to store. While modern operating systems
* can generally make additional space available with swapping, at some
* point there are simply no more bits to allocate. There is also the
* factor of address space limitations, particularly on 32bit machines.
*
* * Platform Factors: Each OS makes use of wildly different memory
* management techniques. These differences result in different performance
* tradeoffs, different fragmentation patterns, and different hard limits
* on the amount of physical and/or virtual memory that we can use before
* OOMing.
*
*
* Reasons for scheduling GC
* -------------------------
*
* While code generally takes the above factors into account in only an ad-hoc
* fashion, the API forces the user to pick a "reason" for the GC. We have a
* bunch of JS::gcreason reasons in GCAPI.h. These fall into a few categories
* that generally coincide with one or more of the above factors.
*
* Embedding reasons:
*
* 1) Do a GC now because the embedding knows something useful about the
* zone's memory retention state. These are gcreasons like LOAD_END,
* PAGE_HIDE, SET_NEW_DOCUMENT, DOM_UTILS. Mostly, Gecko uses these to
* indicate that a significant fraction of the scheduled zone's memory is
* probably reclaimable.
*
* 2) Do some known amount of GC work now because the embedding knows now is
* a good time to do a long, unblockable operation of a known duration.
* These are INTER_SLICE_GC and REFRESH_FRAME.
*
* Correctness reasons:
*
* 3) Do a GC now because correctness depends on some GC property. For
* example, CC_WAITING is where the embedding requires the mark bits
* to be set correct. Also, EVICT_NURSERY where we need to work on the tenured
* heap.
*
* 4) Do a GC because we are shutting down: e.g. SHUTDOWN_CC or DESTROY_*.
*
* 5) Do a GC because a compartment was accessed between GC slices when we
* would have otherwise discarded it. We have to do a second GC to clean
* it up: e.g. COMPARTMENT_REVIVED.
*
* Emergency Reasons:
*
* 6) Do an all-zones, non-incremental GC now because the embedding knows it
* cannot wait: e.g. MEM_PRESSURE.
*
* 7) OOM when fetching a new Chunk results in a LAST_DITCH GC.
*
* Heap Size Limitation Reasons:
*
* 8) Do an incremental, zonal GC with reason MAYBEGC when we discover that
* the gc's allocated size is approaching the current trigger. This is
* called MAYBEGC because we make this check in the MaybeGC function.
* MaybeGC gets called at the top of the main event loop. Normally, it is
* expected that this callback will keep the heap size limited. It is
* relatively inexpensive, because it is invoked with no JS running and
* thus few stack roots to scan. For this reason, the GC's "trigger" bytes
* is less than the GC's "max" bytes as used by the trigger below.
*
* 9) Do an incremental, zonal GC with reason MAYBEGC when we go to allocate
* a new GC thing and find that the GC heap size has grown beyond the
* configured maximum (JSGC_MAX_BYTES). We trigger this GC by returning
* nullptr and then calling maybeGC at the top level of the allocator.
* This is then guaranteed to fail the "size greater than trigger" check
* above, since trigger is always less than max. After performing the GC,
* the allocator unconditionally returns nullptr to force an OOM exception
* is raised by the script.
*
* Note that this differs from a LAST_DITCH GC where we actually run out
* of memory (i.e., a call to a system allocator fails) when trying to
* allocate. Unlike above, LAST_DITCH GC only happens when we are really
* out of memory, not just when we cross an arbitrary trigger; despite
* this, it may still return an allocation at the end and allow the script
* to continue, if the LAST_DITCH GC was able to free up enough memory.
*
* 10) Do a GC under reason ALLOC_TRIGGER when we are over the GC heap trigger
* limit, but in the allocator rather than in a random call to maybeGC.
* This occurs if we allocate too much before returning to the event loop
* and calling maybeGC; this is extremely common in benchmarks and
* long-running Worker computations. Note that this uses a wildly
* different mechanism from the above in that it sets the interrupt flag
* and does the GC at the next loop head, before the next alloc, or
* maybeGC. The reason for this is that this check is made after the
* allocation and we cannot GC with an uninitialized thing in the heap.
*
* 11) Do an incremental, zonal GC with reason TOO_MUCH_MALLOC when we have
* malloced more than JSGC_MAX_MALLOC_BYTES in a zone since the last GC.
*
*
* Size Limitation Triggers Explanation
* ------------------------------------
*
* The GC internally is entirely unaware of the context of the execution of
* the mutator. It sees only:
*
* A) Allocated size: this is the amount of memory currently requested by the
* mutator. This quantity is monotonically increasing: i.e. the allocation
* rate is always >= 0. It is also easy for the system to track.
*
* B) Retained size: this is the amount of memory that the mutator can
* currently reach. Said another way, it is the size of the heap
* immediately after a GC (modulo background sweeping). This size is very
* costly to know exactly and also extremely hard to estimate with any
* fidelity.
*
* For reference, a common allocated vs. retained graph might look like:
*
* | ** **
* | ** ** * **
* | ** * ** * **
* | * ** * ** * **
* | ** ** * ** * **
* s| * * ** ** + + **
* i| * * * + + + + +
* z| * * * + + + + +
* e| * **+
* | * +
* | * +
* | * +
* | * +
* | * +
* |*+
* +--------------------------------------------------
* time
* *** = allocated
* +++ = retained
*
* Note that this is a bit of a simplification
* because in reality we track malloc and GC heap
* sizes separately and have a different level of
* granularity and accuracy on each heap.
*
* This presents some obvious implications for Mark-and-Sweep collectors.
* Namely:
* -> t[marking] ~= size[retained]
* -> t[sweeping] ~= size[allocated] - size[retained]
*
* In a non-incremental collector, maintaining low latency and high
* responsiveness requires that total GC times be as low as possible. Thus,
* in order to stay responsive when we did not have a fully incremental
* collector, our GC triggers were focused on minimizing collection time.
* Furthermore, since size[retained] is not under control of the GC, all the
* GC could do to control collection times was reduce sweep times by
* minimizing size[allocated], per the equation above.
*
* The result of the above is GC triggers that focus on size[allocated] to
* the exclusion of other important factors and default heuristics that are
* not optimal for a fully incremental collector. On the other hand, this is
* not all bad: minimizing size[allocated] also minimizes the chance of OOM
* and sweeping remains one of the hardest areas to further incrementalize.
*
* EAGER_ALLOC_TRIGGER
* -------------------
* Occurs when we return to the event loop and find our heap is getting
* largish, but before t[marking] OR t[sweeping] is too large for a
* responsive non-incremental GC. This is intended to be the common case
* in normal web applications: e.g. we just finished an event handler and
* the few objects we allocated when computing the new whatzitz have
* pushed us slightly over the limit. After this GC we rescale the new
* EAGER_ALLOC_TRIGGER trigger to 150% of size[retained] so that our
* non-incremental GC times will always be proportional to this size
* rather than being dominated by sweeping.
*
* As a concession to mutators that allocate heavily during their startup
* phase, we have a highFrequencyGCMode that ups the growth rate to 300%
* of the current size[retained] so that we'll do fewer longer GCs at the
* end of the mutator startup rather than more, smaller GCs.
*
* Assumptions:
* -> Responsiveness is proportional to t[marking] + t[sweeping].
* -> size[retained] is proportional only to GC allocations.
*
* ALLOC_TRIGGER (non-incremental)
* -------------------------------
* If we do not return to the event loop before getting all the way to our
* gc trigger bytes then MAYBEGC will never fire. To avoid OOMing, we
* succeed the current allocation and set the script interrupt so that we
* will (hopefully) do a GC before we overflow our max and have to raise
* an OOM exception for the script.
*
* Assumptions:
* -> Common web scripts will return to the event loop before using
* 10% of the current gcTriggerBytes worth of GC memory.
*
* ALLOC_TRIGGER (incremental)
* ---------------------------
* In practice the above trigger is rough: if a website is just on the
* cusp, sometimes it will trigger a non-incremental GC moments before
* returning to the event loop, where it could have done an incremental
* GC. Thus, we recently added an incremental version of the above with a
* substantially lower threshold, so that we have a soft limit here. If
* IGC can collect faster than the allocator generates garbage, even if
* the allocator does not return to the event loop frequently, we should
* not have to fall back to a non-incremental GC.
*
* INCREMENTAL_TOO_SLOW
* --------------------
* Do a full, non-incremental GC if we overflow ALLOC_TRIGGER during an
* incremental GC. When in the middle of an incremental GC, we suppress
* our other triggers, so we need a way to backstop the IGC if the
* mutator allocates faster than the IGC can clean things up.
*
* TOO_MUCH_MALLOC
* ---------------
* Performs a GC before size[allocated] - size[retained] gets too large
* for non-incremental sweeping to be fast in the case that we have
* significantly more malloc allocation than GC allocation. This is meant
* to complement MAYBEGC triggers. We track this by counting malloced
* bytes; the counter gets reset at every GC since we do not always have a
* size at the time we call free. Because of this, the malloc heuristic
* is, unfortunatly, not usefully able to augment our other GC heap
* triggers and is limited to this singular heuristic.
*
* Assumptions:
* -> EITHER size[allocated_by_malloc] ~= size[allocated_by_GC]
* OR time[sweeping] ~= size[allocated_by_malloc]
* -> size[retained] @ t0 ~= size[retained] @ t1
* i.e. That the mutator is in steady-state operation.
*
* LAST_DITCH_GC
* -------------
* Does a GC because we are out of memory.
*
* Assumptions:
* -> size[retained] < size[available_memory]
*/
class GCSchedulingState
{
/*
* Influences how we schedule and run GC's in several subtle ways. The most
* important factor is in how it controls the "HeapGrowthFactor". The
* growth factor is a measure of how large (as a percentage of the last GC)
* the heap is allowed to grow before we try to schedule another GC.
*/
bool inHighFrequencyGCMode_;
public:
GCSchedulingState()
: inHighFrequencyGCMode_(false)
{}
bool inHighFrequencyGCMode() const { return inHighFrequencyGCMode_; }
void updateHighFrequencyMode(uint64_t lastGCTime, uint64_t currentTime,
const GCSchedulingTunables& tunables) {
inHighFrequencyGCMode_ =
tunables.isDynamicHeapGrowthEnabled() && lastGCTime &&
lastGCTime + tunables.highFrequencyThresholdUsec() > currentTime;
}
};
template<typename F>
struct Callback {
F op;
void* data;
Callback()
: op(nullptr), data(nullptr)
{}
Callback(F op, void* data)
: op(op), data(data)
{}
};
template<typename F>
using CallbackVector = Vector<Callback<F>, 4, SystemAllocPolicy>;
template <typename T, typename Iter0, typename Iter1>
class ChainedIter
{
Iter0 iter0_;
Iter1 iter1_;
public:
ChainedIter(const Iter0& iter0, const Iter1& iter1)
: iter0_(iter0), iter1_(iter1)
{}
bool done() const { return iter0_.done() && iter1_.done(); }
void next() {
MOZ_ASSERT(!done());
if (!iter0_.done()) {
iter0_.next();
} else {
MOZ_ASSERT(!iter1_.done());
iter1_.next();
}
}
T get() const {
MOZ_ASSERT(!done());
if (!iter0_.done())
return iter0_.get();
MOZ_ASSERT(!iter1_.done());
return iter1_.get();
}
operator T() const { return get(); }
T operator->() const { return get(); }
};
typedef HashMap<Value*, const char*, DefaultHasher<Value*>, SystemAllocPolicy> RootedValueMap;
using AllocKinds = mozilla::EnumSet<AllocKind>;
class GCRuntime
{
public:
explicit GCRuntime(JSRuntime* rt);
MOZ_MUST_USE bool init(uint32_t maxbytes, uint32_t maxNurseryBytes);
void finishRoots();
void finish();
inline bool hasZealMode(ZealMode mode);
inline void clearZealMode(ZealMode mode);
inline bool upcomingZealousGC();
inline bool needZealousGC();
MOZ_MUST_USE bool addRoot(Value* vp, const char* name);
void removeRoot(Value* vp);
void setMarkStackLimit(size_t limit, AutoLockGC& lock);
MOZ_MUST_USE bool setParameter(JSGCParamKey key, uint32_t value, AutoLockGC& lock);
uint32_t getParameter(JSGCParamKey key, const AutoLockGC& lock);
MOZ_MUST_USE bool triggerGC(JS::gcreason::Reason reason);
void maybeAllocTriggerZoneGC(Zone* zone, const AutoLockGC& lock);
// The return value indicates if we were able to do the GC.
bool triggerZoneGC(Zone* zone, JS::gcreason::Reason reason);
void maybeGC(Zone* zone);
void minorGC(JS::gcreason::Reason reason,
gcstats::Phase phase = gcstats::PHASE_MINOR_GC) JS_HAZ_GC_CALL;
void evictNursery(JS::gcreason::Reason reason = JS::gcreason::EVICT_NURSERY) {
minorGC(reason, gcstats::PHASE_EVICT_NURSERY);
}
// The return value indicates whether a major GC was performed.
bool gcIfRequested();
void gc(JSGCInvocationKind gckind, JS::gcreason::Reason reason);
void startGC(JSGCInvocationKind gckind, JS::gcreason::Reason reason, int64_t millis = 0);
void gcSlice(JS::gcreason::Reason reason, int64_t millis = 0);
void finishGC(JS::gcreason::Reason reason);
void abortGC();
void startDebugGC(JSGCInvocationKind gckind, SliceBudget& budget);
void debugGCSlice(SliceBudget& budget);
void triggerFullGCForAtoms() {
MOZ_ASSERT(fullGCForAtomsRequested_);
fullGCForAtomsRequested_ = false;
MOZ_RELEASE_ASSERT(triggerGC(JS::gcreason::ALLOC_TRIGGER));
}
void runDebugGC();
inline void poke();
enum TraceOrMarkRuntime {
TraceRuntime,
MarkRuntime
};
void traceRuntime(JSTracer* trc, AutoLockForExclusiveAccess& lock);
void traceRuntimeForMinorGC(JSTracer* trc, AutoLockForExclusiveAccess& lock);
void notifyDidPaint();
void shrinkBuffers();
void onOutOfMallocMemory();
void onOutOfMallocMemory(const AutoLockGC& lock);
#ifdef JS_GC_ZEAL
const void* addressOfZealModeBits() { return &zealModeBits; }
void getZealBits(uint32_t* zealBits, uint32_t* frequency, uint32_t* nextScheduled);
void setZeal(uint8_t zeal, uint32_t frequency);
bool parseAndSetZeal(const char* str);
void setNextScheduled(uint32_t count);
void verifyPreBarriers();
void maybeVerifyPreBarriers(bool always);
bool selectForMarking(JSObject* object);
void clearSelectedForMarking();
void setDeterministic(bool enable);
#endif
size_t maxMallocBytesAllocated() { return maxMallocBytes; }
uint64_t nextCellUniqueId() {
MOZ_ASSERT(nextCellUniqueId_ > 0);
uint64_t uid = ++nextCellUniqueId_;
return uid;
}
#ifdef DEBUG
bool shutdownCollectedEverything() const {
return arenasEmptyAtShutdown;
}
#endif
public:
// Internal public interface
State state() const { return incrementalState; }
bool isHeapCompacting() const { return state() == State::Compact; }
bool isForegroundSweeping() const { return state() == State::Sweep; }
bool isBackgroundSweeping() { return helperState.isBackgroundSweeping(); }
void waitBackgroundSweepEnd() { helperState.waitBackgroundSweepEnd(); }
void waitBackgroundSweepOrAllocEnd() {
helperState.waitBackgroundSweepEnd();
allocTask.cancel(GCParallelTask::CancelAndWait);
}
void requestMinorGC(JS::gcreason::Reason reason);
#ifdef DEBUG
bool onBackgroundThread() { return helperState.onBackgroundThread(); }
#endif // DEBUG
void lockGC() {
lock.lock();
}
void unlockGC() {
lock.unlock();
}
#ifdef DEBUG
bool isAllocAllowed() { return noGCOrAllocationCheck == 0; }
void disallowAlloc() { ++noGCOrAllocationCheck; }
void allowAlloc() {
MOZ_ASSERT(!isAllocAllowed());
--noGCOrAllocationCheck;
}
bool isNurseryAllocAllowed() { return noNurseryAllocationCheck == 0; }
void disallowNurseryAlloc() { ++noNurseryAllocationCheck; }
void allowNurseryAlloc() {
MOZ_ASSERT(!isNurseryAllocAllowed());
--noNurseryAllocationCheck;
}
bool isStrictProxyCheckingEnabled() { return disableStrictProxyCheckingCount == 0; }
void disableStrictProxyChecking() { ++disableStrictProxyCheckingCount; }
void enableStrictProxyChecking() {
MOZ_ASSERT(disableStrictProxyCheckingCount > 0);
--disableStrictProxyCheckingCount;
}
#endif // DEBUG
bool isInsideUnsafeRegion() { return inUnsafeRegion != 0; }
void enterUnsafeRegion() { ++inUnsafeRegion; }
void leaveUnsafeRegion() {
MOZ_ASSERT(inUnsafeRegion > 0);
--inUnsafeRegion;
}
void verifyIsSafeToGC() {
MOZ_DIAGNOSTIC_ASSERT(!isInsideUnsafeRegion(),
"[AutoAssertNoGC] possible GC in GC-unsafe region");
}
void setAlwaysPreserveCode() { alwaysPreserveCode = true; }
bool isIncrementalGCAllowed() const { return incrementalAllowed; }
void disallowIncrementalGC() { incrementalAllowed = false; }
bool isIncrementalGCEnabled() const { return mode == JSGC_MODE_INCREMENTAL && incrementalAllowed; }
bool isIncrementalGCInProgress() const { return state() != State::NotActive; }
bool isGenerationalGCEnabled() const { return generationalDisabled == 0; }
void disableGenerationalGC();
void enableGenerationalGC();
void disableCompactingGC();
void enableCompactingGC();
bool isCompactingGCEnabled() const;
void setGrayRootsTracer(JSTraceDataOp traceOp, void* data);
MOZ_MUST_USE bool addBlackRootsTracer(JSTraceDataOp traceOp, void* data);
void removeBlackRootsTracer(JSTraceDataOp traceOp, void* data);
void setMaxMallocBytes(size_t value);
int32_t getMallocBytes() const { return mallocBytesUntilGC; }
void resetMallocBytes();
bool isTooMuchMalloc() const { return mallocBytesUntilGC <= 0; }
void updateMallocCounter(JS::Zone* zone, size_t nbytes);
void onTooMuchMalloc();
void setGCCallback(JSGCCallback callback, void* data);
void callGCCallback(JSGCStatus status) const;
void setObjectsTenuredCallback(JSObjectsTenuredCallback callback,
void* data);
void callObjectsTenuredCallback();
MOZ_MUST_USE bool addFinalizeCallback(JSFinalizeCallback callback, void* data);
void removeFinalizeCallback(JSFinalizeCallback func);
MOZ_MUST_USE bool addWeakPointerZoneGroupCallback(JSWeakPointerZoneGroupCallback callback,
void* data);
void removeWeakPointerZoneGroupCallback(JSWeakPointerZoneGroupCallback callback);
MOZ_MUST_USE bool addWeakPointerCompartmentCallback(JSWeakPointerCompartmentCallback callback,
void* data);
void removeWeakPointerCompartmentCallback(JSWeakPointerCompartmentCallback callback);
JS::GCSliceCallback setSliceCallback(JS::GCSliceCallback callback);
JS::GCNurseryCollectionCallback setNurseryCollectionCallback(
JS::GCNurseryCollectionCallback callback);
JS::DoCycleCollectionCallback setDoCycleCollectionCallback(JS::DoCycleCollectionCallback callback);
void callDoCycleCollectionCallback(JSContext* cx);
void setFullCompartmentChecks(bool enable);
bool isManipulatingDeadZones() { return manipulatingDeadZones; }
void setManipulatingDeadZones(bool value) { manipulatingDeadZones = value; }
unsigned objectsMarkedInDeadZonesCount() { return objectsMarkedInDeadZones; }
void incObjectsMarkedInDeadZone() {
MOZ_ASSERT(manipulatingDeadZones);
++objectsMarkedInDeadZones;
}
JS::Zone* getCurrentZoneGroup() { return currentZoneGroup; }
void setFoundBlackGrayEdges(TenuredCell& target) {
AutoEnterOOMUnsafeRegion oomUnsafe;
if (!foundBlackGrayEdges.append(&target))
oomUnsafe.crash("OOM|small: failed to insert into foundBlackGrayEdges");
}
uint64_t gcNumber() const { return number; }
uint64_t minorGCCount() const { return minorGCNumber; }
void incMinorGcNumber() { ++minorGCNumber; ++number; }
uint64_t majorGCCount() const { return majorGCNumber; }
void incMajorGcNumber() { ++majorGCNumber; ++number; }
int64_t defaultSliceBudget() const { return defaultTimeBudget_; }
bool isIncrementalGc() const { return isIncremental; }
bool isFullGc() const { return isFull; }
bool isCompactingGc() const { return isCompacting; }
bool minorGCRequested() const { return minorGCTriggerReason != JS::gcreason::NO_REASON; }
bool majorGCRequested() const { return majorGCTriggerReason != JS::gcreason::NO_REASON; }
bool isGcNeeded() { return minorGCRequested() || majorGCRequested(); }
bool fullGCForAtomsRequested() const { return fullGCForAtomsRequested_; }
double computeHeapGrowthFactor(size_t lastBytes);
size_t computeTriggerBytes(double growthFactor, size_t lastBytes);
JSGCMode gcMode() const { return mode; }
void setGCMode(JSGCMode m) {
mode = m;
marker.setGCMode(mode);
}
inline void updateOnFreeArenaAlloc(const ChunkInfo& info);
inline void updateOnArenaFree(const ChunkInfo& info);
ChunkPool& fullChunks(const AutoLockGC& lock) { return fullChunks_; }
ChunkPool& availableChunks(const AutoLockGC& lock) { return availableChunks_; }
ChunkPool& emptyChunks(const AutoLockGC& lock) { return emptyChunks_; }
const ChunkPool& fullChunks(const AutoLockGC& lock) const { return fullChunks_; }
const ChunkPool& availableChunks(const AutoLockGC& lock) const { return availableChunks_; }
const ChunkPool& emptyChunks(const AutoLockGC& lock) const { return emptyChunks_; }
typedef ChainedIter<Chunk*, ChunkPool::Iter, ChunkPool::Iter> NonEmptyChunksIter;
NonEmptyChunksIter allNonEmptyChunks() {
return NonEmptyChunksIter(ChunkPool::Iter(availableChunks_), ChunkPool::Iter(fullChunks_));
}
Chunk* getOrAllocChunk(const AutoLockGC& lock,
AutoMaybeStartBackgroundAllocation& maybeStartBGAlloc);
void recycleChunk(Chunk* chunk, const AutoLockGC& lock);
#ifdef JS_GC_ZEAL
void startVerifyPreBarriers();
void endVerifyPreBarriers();
void finishVerifier();
bool isVerifyPreBarriersEnabled() const { return !!verifyPreData; }
#else
bool isVerifyPreBarriersEnabled() const { return false; }
#endif
// Free certain LifoAlloc blocks when it is safe to do so.
void freeUnusedLifoBlocksAfterSweeping(LifoAlloc* lifo);
void freeAllLifoBlocksAfterSweeping(LifoAlloc* lifo);
void freeAllLifoBlocksAfterMinorGC(LifoAlloc* lifo);
// Queue a thunk to run after the next minor GC.
void callAfterMinorGC(void (*thunk)(void* data), void* data) {
nursery.queueSweepAction(thunk, data);
}
// Public here for ReleaseArenaLists and FinalizeTypedArenas.
void releaseArena(Arena* arena, const AutoLockGC& lock);
void releaseHeldRelocatedArenas();
void releaseHeldRelocatedArenasWithoutUnlocking(const AutoLockGC& lock);
// Allocator
template <AllowGC allowGC>
MOZ_MUST_USE bool checkAllocatorState(JSContext* cx, AllocKind kind);
template <AllowGC allowGC>
JSObject* tryNewNurseryObject(JSContext* cx, size_t thingSize, size_t nDynamicSlots,
const Class* clasp);
template <AllowGC allowGC>
static JSObject* tryNewTenuredObject(ExclusiveContext* cx, AllocKind kind, size_t thingSize,
size_t nDynamicSlots);
template <typename T, AllowGC allowGC>
static T* tryNewTenuredThing(ExclusiveContext* cx, AllocKind kind, size_t thingSize);
static TenuredCell* refillFreeListInGC(Zone* zone, AllocKind thingKind);
private:
enum IncrementalProgress
{
NotFinished = 0,
Finished
};
// For ArenaLists::allocateFromArena()
friend class ArenaLists;
Chunk* pickChunk(const AutoLockGC& lock,
AutoMaybeStartBackgroundAllocation& maybeStartBGAlloc);
Arena* allocateArena(Chunk* chunk, Zone* zone, AllocKind kind,
ShouldCheckThresholds checkThresholds, const AutoLockGC& lock);
void arenaAllocatedDuringGC(JS::Zone* zone, Arena* arena);
// Allocator internals
MOZ_MUST_USE bool gcIfNeededPerAllocation(JSContext* cx);
template <typename T>
static void checkIncrementalZoneState(ExclusiveContext* cx, T* t);
static TenuredCell* refillFreeListFromAnyThread(ExclusiveContext* cx, AllocKind thingKind,
size_t thingSize);
static TenuredCell* refillFreeListFromMainThread(JSContext* cx, AllocKind thingKind,
size_t thingSize);
static TenuredCell* refillFreeListOffMainThread(ExclusiveContext* cx, AllocKind thingKind);
/*
* Return the list of chunks that can be released outside the GC lock.
* Must be called either during the GC or with the GC lock taken.
*/
friend class BackgroundDecommitTask;
ChunkPool expireEmptyChunkPool(const AutoLockGC& lock);
void freeEmptyChunks(JSRuntime* rt, const AutoLockGC& lock);
void prepareToFreeChunk(ChunkInfo& info);
friend class BackgroundAllocTask;
friend class AutoMaybeStartBackgroundAllocation;
bool wantBackgroundAllocation(const AutoLockGC& lock) const;
void startBackgroundAllocTaskIfIdle();
void requestMajorGC(JS::gcreason::Reason reason);
SliceBudget defaultBudget(JS::gcreason::Reason reason, int64_t millis);
void budgetIncrementalGC(SliceBudget& budget, AutoLockForExclusiveAccess& lock);
void resetIncrementalGC(AbortReason reason, AutoLockForExclusiveAccess& lock);
// Assert if the system state is such that we should never
// receive a request to do GC work.
void checkCanCallAPI();
// Check if the system state is such that GC has been supressed
// or otherwise delayed.
MOZ_MUST_USE bool checkIfGCAllowedInCurrentState(JS::gcreason::Reason reason);
gcstats::ZoneGCStats scanZonesBeforeGC();
void collect(bool nonincrementalByAPI, SliceBudget budget, JS::gcreason::Reason reason) JS_HAZ_GC_CALL;
MOZ_MUST_USE bool gcCycle(bool nonincrementalByAPI, SliceBudget& budget,
JS::gcreason::Reason reason);
void incrementalCollectSlice(SliceBudget& budget, JS::gcreason::Reason reason,
AutoLockForExclusiveAccess& lock);
void pushZealSelectedObjects();
void purgeRuntime(AutoLockForExclusiveAccess& lock);
MOZ_MUST_USE bool beginMarkPhase(JS::gcreason::Reason reason, AutoLockForExclusiveAccess& lock);
bool shouldPreserveJITCode(JSCompartment* comp, int64_t currentTime,
JS::gcreason::Reason reason, bool canAllocateMoreCode);
void traceRuntimeForMajorGC(JSTracer* trc, AutoLockForExclusiveAccess& lock);
void traceRuntimeAtoms(JSTracer* trc, AutoLockForExclusiveAccess& lock);
void traceRuntimeCommon(JSTracer* trc, TraceOrMarkRuntime traceOrMark,
AutoLockForExclusiveAccess& lock);
void bufferGrayRoots();
void maybeDoCycleCollection();
void markCompartments();
IncrementalProgress drainMarkStack(SliceBudget& sliceBudget, gcstats::Phase phase);
template <class CompartmentIterT> void markWeakReferences(gcstats::Phase phase);
void markWeakReferencesInCurrentGroup(gcstats::Phase phase);
template <class ZoneIterT, class CompartmentIterT> void markGrayReferences(gcstats::Phase phase);
void markBufferedGrayRoots(JS::Zone* zone);
void markGrayReferencesInCurrentGroup(gcstats::Phase phase);
void markAllWeakReferences(gcstats::Phase phase);
void markAllGrayReferences(gcstats::Phase phase);
void beginSweepPhase(bool lastGC, AutoLockForExclusiveAccess& lock);
void findZoneGroups(AutoLockForExclusiveAccess& lock);
MOZ_MUST_USE bool findZoneEdgesForWeakMaps();
void getNextZoneGroup();
void endMarkingZoneGroup();
void beginSweepingZoneGroup(AutoLockForExclusiveAccess& lock);
bool shouldReleaseObservedTypes();
void endSweepingZoneGroup();
IncrementalProgress sweepPhase(SliceBudget& sliceBudget, AutoLockForExclusiveAccess& lock);
void endSweepPhase(bool lastGC, AutoLockForExclusiveAccess& lock);
void sweepZones(FreeOp* fop, bool lastGC);
void decommitAllWithoutUnlocking(const AutoLockGC& lock);
void startDecommit();
void queueZonesForBackgroundSweep(ZoneList& zones);
void sweepBackgroundThings(ZoneList& zones, LifoAlloc& freeBlocks);
void assertBackgroundSweepingFinished();
bool shouldCompact();
void beginCompactPhase();
IncrementalProgress compactPhase(JS::gcreason::Reason reason, SliceBudget& sliceBudget,
AutoLockForExclusiveAccess& lock);
void endCompactPhase(JS::gcreason::Reason reason);
void sweepTypesAfterCompacting(Zone* zone);
void sweepZoneAfterCompacting(Zone* zone);
MOZ_MUST_USE bool relocateArenas(Zone* zone, JS::gcreason::Reason reason,
Arena*& relocatedListOut, SliceBudget& sliceBudget);
void updateTypeDescrObjects(MovingTracer* trc, Zone* zone);
void updateCellPointers(MovingTracer* trc, Zone* zone, AllocKinds kinds, size_t bgTaskCount);
void updateAllCellPointers(MovingTracer* trc, Zone* zone);
void updatePointersToRelocatedCells(Zone* zone, AutoLockForExclusiveAccess& lock);
void protectAndHoldArenas(Arena* arenaList);
void unprotectHeldRelocatedArenas();
void releaseRelocatedArenas(Arena* arenaList);
void releaseRelocatedArenasWithoutUnlocking(Arena* arenaList, const AutoLockGC& lock);
void finishCollection(JS::gcreason::Reason reason);
void computeNonIncrementalMarkingForValidation(AutoLockForExclusiveAccess& lock);
void validateIncrementalMarking();
void finishMarkingValidation();
#ifdef DEBUG
void checkForCompartmentMismatches();
#endif
void callFinalizeCallbacks(FreeOp* fop, JSFinalizeStatus status) const;
void callWeakPointerZoneGroupCallbacks() const;
void callWeakPointerCompartmentCallbacks(JSCompartment* comp) const;
public:
JSRuntime* rt;
/* Embedders can use this zone however they wish. */
JS::Zone* systemZone;
/* List of compartments and zones (protected by the GC lock). */
ZoneVector zones;
Nursery nursery;
StoreBuffer storeBuffer;
gcstats::Statistics stats;
GCMarker marker;
/* Track heap usage for this runtime. */
HeapUsage usage;
/* GC scheduling state and parameters. */
GCSchedulingTunables tunables;
GCSchedulingState schedulingState;
MemProfiler mMemProfiler;
private:
// When empty, chunks reside in the emptyChunks pool and are re-used as
// needed or eventually expired if not re-used. The emptyChunks pool gets
// refilled from the background allocation task heuristically so that empty
// chunks should always available for immediate allocation without syscalls.
ChunkPool emptyChunks_;
// Chunks which have had some, but not all, of their arenas allocated live
// in the available chunk lists. When all available arenas in a chunk have
// been allocated, the chunk is removed from the available list and moved
// to the fullChunks pool. During a GC, if all arenas are free, the chunk
// is moved back to the emptyChunks pool and scheduled for eventual
// release.
ChunkPool availableChunks_;
// When all arenas in a chunk are used, it is moved to the fullChunks pool
// so as to reduce the cost of operations on the available lists.
ChunkPool fullChunks_;
RootedValueMap rootsHash;
size_t maxMallocBytes;
// An incrementing id used to assign unique ids to cells that require one.
mozilla::Atomic<uint64_t, mozilla::ReleaseAcquire> nextCellUniqueId_;
/*
* Number of the committed arenas in all GC chunks including empty chunks.
*/
mozilla::Atomic<uint32_t, mozilla::ReleaseAcquire> numArenasFreeCommitted;
VerifyPreTracer* verifyPreData;
private:
bool chunkAllocationSinceLastGC;
int64_t lastGCTime;
JSGCMode mode;
mozilla::Atomic<size_t, mozilla::ReleaseAcquire> numActiveZoneIters;
/* During shutdown, the GC needs to clean up every possible object. */
bool cleanUpEverything;
// Gray marking must be done after all black marking is complete. However,
// we do not have write barriers on XPConnect roots. Therefore, XPConnect
// roots must be accumulated in the first slice of incremental GC. We
// accumulate these roots in each zone's gcGrayRoots vector and then mark
// them later, after black marking is complete for each compartment. This
// accumulation can fail, but in that case we switch to non-incremental GC.
enum class GrayBufferState {
Unused,
Okay,
Failed
};
GrayBufferState grayBufferState;
bool hasBufferedGrayRoots() const { return grayBufferState == GrayBufferState::Okay; }
// Clear each zone's gray buffers, but do not change the current state.
void resetBufferedGrayRoots() const;
// Reset the gray buffering state to Unused.
void clearBufferedGrayRoots() {
grayBufferState = GrayBufferState::Unused;
resetBufferedGrayRoots();
}
mozilla::Atomic<JS::gcreason::Reason, mozilla::Relaxed> majorGCTriggerReason;
JS::gcreason::Reason minorGCTriggerReason;
/* Perform full GC if rt->keepAtoms() becomes false. */
bool fullGCForAtomsRequested_;
/* Incremented at the start of every minor GC. */
uint64_t minorGCNumber;
/* Incremented at the start of every major GC. */
uint64_t majorGCNumber;
/* The major GC number at which to release observed type information. */
uint64_t jitReleaseNumber;
/* Incremented on every GC slice. */
uint64_t number;
/* The number at the time of the most recent GC's first slice. */
uint64_t startNumber;
/* Whether the currently running GC can finish in multiple slices. */
bool isIncremental;
/* Whether all zones are being collected in first GC slice. */
bool isFull;
/* Whether the heap will be compacted at the end of GC. */
bool isCompacting;
/* The invocation kind of the current GC, taken from the first slice. */
JSGCInvocationKind invocationKind;
/* The initial GC reason, taken from the first slice. */
JS::gcreason::Reason initialReason;
#ifdef DEBUG
/*
* If this is 0, all cross-compartment proxies must be registered in the
* wrapper map. This checking must be disabled temporarily while creating
* new wrappers. When non-zero, this records the recursion depth of wrapper
* creation.
*/
uintptr_t disableStrictProxyCheckingCount;
#endif
/*
* The current incremental GC phase. This is also used internally in
* non-incremental GC.
*/
State incrementalState;
/* Indicates that the last incremental slice exhausted the mark stack. */
bool lastMarkSlice;
/* Whether any sweeping will take place in the separate GC helper thread. */
bool sweepOnBackgroundThread;
/* Whether observed type information is being released in the current GC. */
bool releaseObservedTypes;
/* Whether any black->gray edges were found during marking. */
BlackGrayEdgeVector foundBlackGrayEdges;
/* Singly linekd list of zones to be swept in the background. */
ZoneList backgroundSweepZones;
/*
* Free LIFO blocks are transferred to this allocator before being freed on
* the background GC thread after sweeping.
*/
LifoAlloc blocksToFreeAfterSweeping;
/*
* Free LIFO blocks are transferred to this allocator before being freed
* after minor GC.
*/
LifoAlloc blocksToFreeAfterMinorGC;
/* Index of current zone group (for stats). */
unsigned zoneGroupIndex;
/*
* Incremental sweep state.
*/
JS::Zone* zoneGroups;
JS::Zone* currentZoneGroup;
bool sweepingTypes;
unsigned finalizePhase;
JS::Zone* sweepZone;
AllocKind sweepKind;
bool abortSweepAfterCurrentGroup;
/*
* Concurrent sweep infrastructure.
*/
void startTask(GCParallelTask& task, gcstats::Phase phase, AutoLockHelperThreadState& locked);
void joinTask(GCParallelTask& task, gcstats::Phase phase, AutoLockHelperThreadState& locked);
/*
* List head of arenas allocated during the sweep phase.
*/
Arena* arenasAllocatedDuringSweep;
/*
* Incremental compacting state.
*/
bool startedCompacting;
ZoneList zonesToMaybeCompact;
Arena* relocatedArenasToRelease;
#ifdef JS_GC_ZEAL
MarkingValidator* markingValidator;
#endif
/*
* Indicates that a GC slice has taken place in the middle of an animation
* frame, rather than at the beginning. In this case, the next slice will be
* delayed so that we don't get back-to-back slices.
*/
bool interFrameGC;
/* Default budget for incremental GC slice. See js/SliceBudget.h. */
int64_t defaultTimeBudget_;
/*
* We disable incremental GC if we encounter a Class with a trace hook
* that does not implement write barriers.
*/
bool incrementalAllowed;
/*
* GGC can be enabled from the command line while testing.
*/
unsigned generationalDisabled;
/*
* Whether compacting GC can is enabled globally.
*/
bool compactingEnabled;
/*
* Some code cannot tolerate compacting GC so it can be disabled temporarily
* with AutoDisableCompactingGC which uses this counter.
*/
unsigned compactingDisabledCount;
/*
* This is true if we are in the middle of a brain transplant (e.g.,
* JS_TransplantObject) or some other operation that can manipulate
* dead zones.
*/
bool manipulatingDeadZones;
/*
* This field is incremented each time we mark an object inside a
* zone with no incoming cross-compartment pointers. Typically if
* this happens it signals that an incremental GC is marking too much
* stuff. At various times we check this counter and, if it has changed, we
* run an immediate, non-incremental GC to clean up the dead
* zones. This should happen very rarely.
*/
unsigned objectsMarkedInDeadZones;
bool poked;
/*
* These options control the zealousness of the GC. At every allocation,
* nextScheduled is decremented. When it reaches zero we do a full GC.
*
* At this point, if zeal_ is one of the types that trigger periodic
* collection, then nextScheduled is reset to the value of zealFrequency.
* Otherwise, no additional GCs take place.
*
* You can control these values in several ways:
* - Set the JS_GC_ZEAL environment variable
* - Call gczeal() or schedulegc() from inside shell-executed JS code
* (see the help for details)
*
* If gcZeal_ == 1 then we perform GCs in select places (during MaybeGC and
* whenever a GC poke happens). This option is mainly useful to embedders.
*
* We use zeal_ == 4 to enable write barrier verification. See the comment
* in jsgc.cpp for more information about this.
*
* zeal_ values from 8 to 10 periodically run different types of
* incremental GC.
*
* zeal_ value 14 performs periodic shrinking collections.
*/
#ifdef JS_GC_ZEAL
uint32_t zealModeBits;
int zealFrequency;
int nextScheduled;
bool deterministicOnly;
int incrementalLimit;
Vector<JSObject*, 0, SystemAllocPolicy> selectedForMarking;
#endif
bool fullCompartmentChecks;
Callback<JSGCCallback> gcCallback;
Callback<JS::DoCycleCollectionCallback> gcDoCycleCollectionCallback;
Callback<JSObjectsTenuredCallback> tenuredCallback;
CallbackVector<JSFinalizeCallback> finalizeCallbacks;
CallbackVector<JSWeakPointerZoneGroupCallback> updateWeakPointerZoneGroupCallbacks;
CallbackVector<JSWeakPointerCompartmentCallback> updateWeakPointerCompartmentCallbacks;
/*
* Malloc counter to measure memory pressure for GC scheduling. It runs
* from maxMallocBytes down to zero.
*/
mozilla::Atomic<ptrdiff_t, mozilla::ReleaseAcquire> mallocBytesUntilGC;
/*
* Whether a GC has been triggered as a result of mallocBytesUntilGC
* falling below zero.
*/
mozilla::Atomic<bool, mozilla::ReleaseAcquire> mallocGCTriggered;
/*
* The trace operations to trace embedding-specific GC roots. One is for
* tracing through black roots and the other is for tracing through gray
* roots. The black/gray distinction is only relevant to the cycle
* collector.
*/
CallbackVector<JSTraceDataOp> blackRootTracers;
Callback<JSTraceDataOp> grayRootTracer;
/* Always preserve JIT code during GCs, for testing. */
bool alwaysPreserveCode;
/*
* Some regions of code are hard for the static rooting hazard analysis to
* understand. In those cases, we trade the static analysis for a dynamic
* analysis. When this is non-zero, we should assert if we trigger, or
* might trigger, a GC.
*/
int inUnsafeRegion;
#ifdef DEBUG
size_t noGCOrAllocationCheck;
size_t noNurseryAllocationCheck;
bool arenasEmptyAtShutdown;
#endif
/* Synchronize GC heap access between main thread and GCHelperState. */
friend class js::AutoLockGC;
js::Mutex lock;
BackgroundAllocTask allocTask;
BackgroundDecommitTask decommitTask;
GCHelperState helperState;
/*
* During incremental sweeping, this field temporarily holds the arenas of
* the current AllocKind being swept in order of increasing free space.
*/
SortedArenaList incrementalSweepList;
friend class js::GCHelperState;
friend class MarkingValidator;
friend class AutoTraceSession;
friend class AutoEnterIteration;
};
/* Prevent compartments and zones from being collected during iteration. */
class MOZ_RAII AutoEnterIteration {
GCRuntime* gc;
public:
explicit AutoEnterIteration(GCRuntime* gc_) : gc(gc_) {
++gc->numActiveZoneIters;
}
~AutoEnterIteration() {
MOZ_ASSERT(gc->numActiveZoneIters);
--gc->numActiveZoneIters;
}
};
// After pulling a Chunk out of the empty chunks pool, we want to run the
// background allocator to refill it. The code that takes Chunks does so under
// the GC lock. We need to start the background allocation under the helper
// threads lock. To avoid lock inversion we have to delay the start until after
// we are outside the GC lock. This class handles that delay automatically.
class MOZ_RAII AutoMaybeStartBackgroundAllocation
{
GCRuntime* gc;
public:
AutoMaybeStartBackgroundAllocation()
: gc(nullptr)
{}
void tryToStartBackgroundAllocation(GCRuntime& gc) {
this->gc = &gc;
}
~AutoMaybeStartBackgroundAllocation() {
if (gc)
gc->startBackgroundAllocTaskIfIdle();
}
};
#ifdef JS_GC_ZEAL
inline bool
GCRuntime::hasZealMode(ZealMode mode)
{
static_assert(size_t(ZealMode::Limit) < sizeof(zealModeBits) * 8,
"Zeal modes must fit in zealModeBits");
return zealModeBits & (1 << uint32_t(mode));
}
inline void
GCRuntime::clearZealMode(ZealMode mode)
{
zealModeBits &= ~(1 << uint32_t(mode));
MOZ_ASSERT(!hasZealMode(mode));
}
inline bool
GCRuntime::upcomingZealousGC() {
return nextScheduled == 1;
}
inline bool
GCRuntime::needZealousGC() {
if (nextScheduled > 0 && --nextScheduled == 0) {
if (hasZealMode(ZealMode::Alloc) ||
hasZealMode(ZealMode::GenerationalGC) ||
hasZealMode(ZealMode::IncrementalRootsThenFinish) ||
hasZealMode(ZealMode::IncrementalMarkAllThenFinish) ||
hasZealMode(ZealMode::IncrementalMultipleSlices) ||
hasZealMode(ZealMode::Compact))
{
nextScheduled = zealFrequency;
}
return true;
}
return false;
}
#else
inline bool GCRuntime::hasZealMode(ZealMode mode) { return false; }
inline void GCRuntime::clearZealMode(ZealMode mode) { }
inline bool GCRuntime::upcomingZealousGC() { return false; }
inline bool GCRuntime::needZealousGC() { return false; }
#endif
} /* namespace gc */
} /* namespace js */
#endif
