The Tor Browser: js/src/gc/Nursery.cpp@b8a032363ba2 (annotated)

js/src/gc/Nursery.cpp@b8a032363ba2 (annotated)

js/src/gc/Nursery.cpp

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  * vim: set ts=8 sw=4 et tw=78:
  *
  * 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/. */
 #ifdef JSGC_GENERATIONAL
 #include "gc/Nursery-inl.h"
 #include "jscompartment.h"
 #include "jsgc.h"
 #include "jsinfer.h"
 #include "jsutil.h"
 #include "prmjtime.h"
 #include "gc/GCInternals.h"
 #include "gc/Memory.h"
 #ifdef JS_ION
 #include "jit/IonFrames.h"
 #endif
 #include "mozilla/IntegerPrintfMacros.h"
 #include "vm/ArrayObject.h"
 #include "vm/Debugger.h"
 #if defined(DEBUG)
 #include "vm/ScopeObject.h"
 #endif
 #include "vm/TypedArrayObject.h"
 #include "jsgcinlines.h"
 #include "vm/ObjectImpl-inl.h"
 using namespace js;
 using namespace gc;
 using namespace mozilla;
 //#define PROFILE_NURSERY
 #ifdef PROFILE_NURSERY
 /*
  * Print timing information for minor GCs that take longer than this time in microseconds.
  */
 static int64_t GCReportThreshold = INT64_MAX;
 #endif
 bool
 js::Nursery::init()
 {
     JS_ASSERT(start() == 0);
     if (!hugeSlots.init())
         return false;
     void *heap = MapAlignedPages(runtime(), NurserySize, Alignment);
     if (!heap)
         return false;
     JSRuntime *rt = runtime();
     rt->gcNurseryStart_ = uintptr_t(heap);
     currentStart_ = start();
     rt->gcNurseryEnd_ = chunk(LastNurseryChunk).end();
     numActiveChunks_ = 1;
     JS_POISON(heap, JS_FRESH_NURSERY_PATTERN, NurserySize);
     setCurrentChunk(0);
     updateDecommittedRegion();
 #ifdef PROFILE_NURSERY
     char *env = getenv("JS_MINORGC_TIME");
     if (env)
         GCReportThreshold = atoi(env);
 #endif
     JS_ASSERT(isEnabled());
     return true;
 }
 js::Nursery::~Nursery()
 {
     if (start())
         UnmapPages(runtime(), (void *)start(), NurserySize);
 }
 void
 js::Nursery::enable()
 {
     JS_ASSERT(isEmpty());
     if (isEnabled())
         return;
     numActiveChunks_ = 1;
     setCurrentChunk(0);
     currentStart_ = position();
 #ifdef JS_GC_ZEAL
     if (runtime()->gcZeal_ == ZealGenerationalGCValue)
         enterZealMode();
 #endif
 }
 void
 js::Nursery::disable()
 {
     JS_ASSERT(isEmpty());
     if (!isEnabled())
         return;
     numActiveChunks_ = 0;
     currentEnd_ = 0;
     updateDecommittedRegion();
 }
 bool
 js::Nursery::isEmpty() const
 {
     JS_ASSERT(runtime_);
     if (!isEnabled())
         return true;
     JS_ASSERT_IF(runtime_->gcZeal_ != ZealGenerationalGCValue, currentStart_ == start());
     return position() == currentStart_;
 }
 JSObject *
 js::Nursery::allocateObject(JSContext *cx, size_t size, size_t numDynamic)
 {
     /* Ensure there's enough space to replace the contents with a RelocationOverlay. */
     JS_ASSERT(size >= sizeof(RelocationOverlay));
     /* Attempt to allocate slots contiguously after object, if possible. */
     if (numDynamic && numDynamic <= MaxNurserySlots) {
         size_t totalSize = size + sizeof(HeapSlot) * numDynamic;
         JSObject *obj = static_cast<JSObject *>(allocate(totalSize));
         if (obj) {
             obj->setInitialSlots(reinterpret_cast<HeapSlot *>(size_t(obj) + size));
             return obj;
         }
         /* If we failed to allocate as a block, retry with out-of-line slots. */
     }
     HeapSlot *slots = nullptr;
     if (numDynamic) {
         slots = allocateHugeSlots(cx, numDynamic);
         if (MOZ_UNLIKELY(!slots))
             return nullptr;
     }
     JSObject *obj = static_cast<JSObject *>(allocate(size));
     if (obj)
         obj->setInitialSlots(slots);
     else
         freeSlots(cx, slots);
     return obj;
 }
 void *
 js::Nursery::allocate(size_t size)
 {
     JS_ASSERT(isEnabled());
     JS_ASSERT(!runtime()->isHeapBusy());
     JS_ASSERT(position() >= currentStart_);
     if (position() + size > currentEnd()) {
         if (currentChunk_ + 1 == numActiveChunks_)
             return nullptr;
         setCurrentChunk(currentChunk_ + 1);
     }
     void *thing = (void *)position();
     position_ = position() + size;
     JS_EXTRA_POISON(thing, JS_ALLOCATED_NURSERY_PATTERN, size);
     return thing;
 }
 /* Internally, this function is used to allocate elements as well as slots. */
 HeapSlot *
 js::Nursery::allocateSlots(JSContext *cx, JSObject *obj, uint32_t nslots)
 {
     JS_ASSERT(obj);
     JS_ASSERT(nslots > 0);
     if (!isInside(obj))
         return cx->pod_malloc<HeapSlot>(nslots);
     if (nslots > MaxNurserySlots)
         return allocateHugeSlots(cx, nslots);
     size_t size = sizeof(HeapSlot) * nslots;
     HeapSlot *slots = static_cast<HeapSlot *>(allocate(size));
     if (slots)
         return slots;
     return allocateHugeSlots(cx, nslots);
 }
 ObjectElements *
 js::Nursery::allocateElements(JSContext *cx, JSObject *obj, uint32_t nelems)
 {
     JS_ASSERT(nelems >= ObjectElements::VALUES_PER_HEADER);
     return reinterpret_cast<ObjectElements *>(allocateSlots(cx, obj, nelems));
 }
 HeapSlot *
 js::Nursery::reallocateSlots(JSContext *cx, JSObject *obj, HeapSlot *oldSlots,
                              uint32_t oldCount, uint32_t newCount)
 {
     size_t oldSize = oldCount * sizeof(HeapSlot);
     size_t newSize = newCount * sizeof(HeapSlot);
     if (!isInside(obj))
         return static_cast<HeapSlot *>(cx->realloc_(oldSlots, oldSize, newSize));
     if (!isInside(oldSlots)) {
         HeapSlot *newSlots = static_cast<HeapSlot *>(cx->realloc_(oldSlots, oldSize, newSize));
         if (oldSlots != newSlots) {
             hugeSlots.remove(oldSlots);
             /* If this put fails, we will only leak the slots. */
             (void)hugeSlots.put(newSlots);
         }
         return newSlots;
     }
     /* The nursery cannot make use of the returned slots data. */
     if (newCount < oldCount)
         return oldSlots;
     HeapSlot *newSlots = allocateSlots(cx, obj, newCount);
     PodCopy(newSlots, oldSlots, oldCount);
     return newSlots;
 }
 ObjectElements *
 js::Nursery::reallocateElements(JSContext *cx, JSObject *obj, ObjectElements *oldHeader,
                                 uint32_t oldCount, uint32_t newCount)
 {
     HeapSlot *slots = reallocateSlots(cx, obj, reinterpret_cast<HeapSlot *>(oldHeader),
                                       oldCount, newCount);
     return reinterpret_cast<ObjectElements *>(slots);
 }
 void
 js::Nursery::freeSlots(JSContext *cx, HeapSlot *slots)
 {
     if (!isInside(slots)) {
         hugeSlots.remove(slots);
         js_free(slots);
     }
 }
 HeapSlot *
 js::Nursery::allocateHugeSlots(JSContext *cx, size_t nslots)
 {
     HeapSlot *slots = cx->pod_malloc<HeapSlot>(nslots);
     /* If this put fails, we will only leak the slots. */
     (void)hugeSlots.put(slots);
     return slots;
 }
 void
 js::Nursery::notifyInitialSlots(Cell *cell, HeapSlot *slots)
 {
     if (isInside(cell) && !isInside(slots)) {
         /* If this put fails, we will only leak the slots. */
         (void)hugeSlots.put(slots);
     }
 }
 namespace js {
 namespace gc {
 class MinorCollectionTracer : public JSTracer
 {
   public:
     Nursery *nursery;
     AutoTraceSession session;
     /* Amount of data moved to the tenured generation during collection. */
     size_t tenuredSize;
     /*
      * This list is threaded through the Nursery using the space from already
      * moved things. The list is used to fix up the moved things and to find
      * things held live by intra-Nursery pointers.
      */
     RelocationOverlay *head;
     RelocationOverlay **tail;
     /* Save and restore all of the runtime state we use during MinorGC. */
     bool savedRuntimeNeedBarrier;
     AutoDisableProxyCheck disableStrictProxyChecking;
     AutoEnterOOMUnsafeRegion oomUnsafeRegion;
     ArrayBufferVector liveArrayBuffers;
     /* Insert the given relocation entry into the list of things to visit. */
     MOZ_ALWAYS_INLINE void insertIntoFixupList(RelocationOverlay *entry) {
         *tail = entry;
         tail = &entry->next_;
         *tail = nullptr;
     }
     MinorCollectionTracer(JSRuntime *rt, Nursery *nursery)
       : JSTracer(rt, Nursery::MinorGCCallback, TraceWeakMapKeysValues),
         nursery(nursery),
         session(rt, MinorCollecting),
         tenuredSize(0),
         head(nullptr),
         tail(&head),
         savedRuntimeNeedBarrier(rt->needsBarrier()),
         disableStrictProxyChecking(rt)
     {
         rt->gcNumber++;
         /*
          * We disable the runtime needsBarrier() check so that pre-barriers do
          * not fire on objects that have been relocated. The pre-barrier's
          * call to obj->zone() will try to look through shape_, which is now
          * the relocation magic and will crash. However, zone->needsBarrier()
          * must still be set correctly so that allocations we make in minor
          * GCs between incremental slices will allocate their objects marked.
          */
         rt->setNeedsBarrier(false);
         /*
          * We use the live array buffer lists to track traced buffers so we can
          * sweep their dead views. Incremental collection also use these lists,
          * so we may need to save and restore their contents here.
          */
         if (rt->gcIncrementalState != NO_INCREMENTAL) {
             for (GCCompartmentsIter c(rt); !c.done(); c.next()) {
                 if (!ArrayBufferObject::saveArrayBufferList(c, liveArrayBuffers))
                     CrashAtUnhandlableOOM("OOM while saving live array buffers");
                 ArrayBufferObject::resetArrayBufferList(c);
             }
         }
     }
     ~MinorCollectionTracer() {
         runtime()->setNeedsBarrier(savedRuntimeNeedBarrier);
         if (runtime()->gcIncrementalState != NO_INCREMENTAL)
             ArrayBufferObject::restoreArrayBufferLists(liveArrayBuffers);
     }
 };
 } /* namespace gc */
 } /* namespace js */
 static AllocKind
 GetObjectAllocKindForCopy(JSRuntime *rt, JSObject *obj)
 {
     if (obj->is<ArrayObject>()) {
         JS_ASSERT(obj->numFixedSlots() == 0);
         /* Use minimal size object if we are just going to copy the pointer. */
         if (!IsInsideNursery(rt, (void *)obj->getElementsHeader()))
             return FINALIZE_OBJECT0_BACKGROUND;
         size_t nelements = obj->getDenseCapacity();
         return GetBackgroundAllocKind(GetGCArrayKind(nelements));
     }
     if (obj->is<JSFunction>())
         return obj->as<JSFunction>().getAllocKind();
     /*
      * Typed arrays in the nursery may have a lazily allocated buffer, make
      * sure there is room for the array's fixed data when moving the array.
      */
     if (obj->is<TypedArrayObject>() && !obj->as<TypedArrayObject>().buffer()) {
         size_t nbytes = obj->as<TypedArrayObject>().byteLength();
         return GetBackgroundAllocKind(TypedArrayObject::AllocKindForLazyBuffer(nbytes));
     }
     AllocKind kind = GetGCObjectFixedSlotsKind(obj->numFixedSlots());
     JS_ASSERT(!IsBackgroundFinalized(kind));
     JS_ASSERT(CanBeFinalizedInBackground(kind, obj->getClass()));
     return GetBackgroundAllocKind(kind);
 }
 void *
 js::Nursery::allocateFromTenured(Zone *zone, AllocKind thingKind)
 {
     void *t = zone->allocator.arenas.allocateFromFreeList(thingKind, Arena::thingSize(thingKind));
     if (t)
         return t;
     zone->allocator.arenas.checkEmptyFreeList(thingKind);
     return zone->allocator.arenas.allocateFromArena(zone, thingKind);
 }
 void
 js::Nursery::setSlotsForwardingPointer(HeapSlot *oldSlots, HeapSlot *newSlots, uint32_t nslots)
 {
     JS_ASSERT(nslots > 0);
     JS_ASSERT(isInside(oldSlots));
     JS_ASSERT(!isInside(newSlots));
     *reinterpret_cast<HeapSlot **>(oldSlots) = newSlots;
 }
 void
 js::Nursery::setElementsForwardingPointer(ObjectElements *oldHeader, ObjectElements *newHeader,
                                           uint32_t nelems)
 {
     /*
      * If the JIT has hoisted a zero length pointer, then we do not need to
      * relocate it because reads and writes to/from this pointer are invalid.
      */
     if (nelems - ObjectElements::VALUES_PER_HEADER < 1)
         return;
     JS_ASSERT(isInside(oldHeader));
     JS_ASSERT(!isInside(newHeader));
     *reinterpret_cast<HeapSlot **>(oldHeader->elements()) = newHeader->elements();
 }
 #ifdef DEBUG
 static bool IsWriteableAddress(void *ptr)
 {
     volatile uint64_t *vPtr = reinterpret_cast<volatile uint64_t *>(ptr);
     *vPtr = *vPtr;
     return true;
 }
 #endif
 void
 js::Nursery::forwardBufferPointer(HeapSlot **pSlotsElems)
 {
     HeapSlot *old = *pSlotsElems;
     if (!isInside(old))
         return;
     /*
      * If the elements buffer is zero length, the "first" item could be inside
      * of the next object or past the end of the allocable area.  However,
      * since we always store the runtime as the last word in the nursery,
      * isInside will still be true, even if this zero-size allocation abuts the
      * end of the allocable area. Thus, it is always safe to read the first
      * word of |old| here.
      */
     *pSlotsElems = *reinterpret_cast<HeapSlot **>(old);
     JS_ASSERT(!isInside(*pSlotsElems));
     JS_ASSERT(IsWriteableAddress(*pSlotsElems));
 }
 // Structure for counting how many times objects of a particular type have been
 // tenured during a minor collection.
 struct TenureCount
 {
     types::TypeObject *type;
     int count;
 };
 // Keep rough track of how many times we tenure objects of particular types
 // during minor collections, using a fixed size hash for efficiency at the cost
 // of potential collisions.
 struct Nursery::TenureCountCache
 {
     TenureCount entries[16];
     TenureCountCache() { PodZero(this); }
     TenureCount &findEntry(types::TypeObject *type) {
         return entries[PointerHasher<types::TypeObject *, 3>::hash(type) % ArrayLength(entries)];
     }
 };
 void
 js::Nursery::collectToFixedPoint(MinorCollectionTracer *trc, TenureCountCache &tenureCounts)
 {
     for (RelocationOverlay *p = trc->head; p; p = p->next()) {
         JSObject *obj = static_cast<JSObject*>(p->forwardingAddress());
         traceObject(trc, obj);
         TenureCount &entry = tenureCounts.findEntry(obj->type());
         if (entry.type == obj->type()) {
             entry.count++;
         } else if (!entry.type) {
             entry.type = obj->type();
             entry.count = 1;
         }
     }
 }
 MOZ_ALWAYS_INLINE void
 js::Nursery::traceObject(MinorCollectionTracer *trc, JSObject *obj)
 {
     const Class *clasp = obj->getClass();
     if (clasp->trace)
         clasp->trace(trc, obj);
     if (!obj->isNative())
         return;
     if (!obj->hasEmptyElements())
         markSlots(trc, obj->getDenseElements(), obj->getDenseInitializedLength());
     HeapSlot *fixedStart, *fixedEnd, *dynStart, *dynEnd;
     obj->getSlotRange(0, obj->slotSpan(), &fixedStart, &fixedEnd, &dynStart, &dynEnd);
     markSlots(trc, fixedStart, fixedEnd);
     markSlots(trc, dynStart, dynEnd);
 }
 MOZ_ALWAYS_INLINE void
 js::Nursery::markSlots(MinorCollectionTracer *trc, HeapSlot *vp, uint32_t nslots)
 {
     markSlots(trc, vp, vp + nslots);
 }
 MOZ_ALWAYS_INLINE void
 js::Nursery::markSlots(MinorCollectionTracer *trc, HeapSlot *vp, HeapSlot *end)
 {
     for (; vp != end; ++vp)
         markSlot(trc, vp);
 }
 MOZ_ALWAYS_INLINE void
 js::Nursery::markSlot(MinorCollectionTracer *trc, HeapSlot *slotp)
 {
     if (!slotp->isObject())
         return;
     JSObject *obj = &slotp->toObject();
     if (!isInside(obj))
         return;
     if (getForwardedPointer(&obj)) {
         slotp->unsafeGet()->setObject(*obj);
         return;
     }
     JSObject *tenured = static_cast<JSObject*>(moveToTenured(trc, obj));
     slotp->unsafeGet()->setObject(*tenured);
 }
 void *
 js::Nursery::moveToTenured(MinorCollectionTracer *trc, JSObject *src)
 {
     Zone *zone = src->zone();
     AllocKind dstKind = GetObjectAllocKindForCopy(trc->runtime(), src);
     JSObject *dst = static_cast<JSObject *>(allocateFromTenured(zone, dstKind));
     if (!dst)
         CrashAtUnhandlableOOM("Failed to allocate object while tenuring.");
     trc->tenuredSize += moveObjectToTenured(dst, src, dstKind);
     RelocationOverlay *overlay = reinterpret_cast<RelocationOverlay *>(src);
     overlay->forwardTo(dst);
     trc->insertIntoFixupList(overlay);
     return static_cast<void *>(dst);
 }
 size_t
 js::Nursery::moveObjectToTenured(JSObject *dst, JSObject *src, AllocKind dstKind)
 {
     size_t srcSize = Arena::thingSize(dstKind);
     size_t tenuredSize = srcSize;
     /*
      * Arrays do not necessarily have the same AllocKind between src and dst.
      * We deal with this by copying elements manually, possibly re-inlining
      * them if there is adequate room inline in dst.
      */
     if (src->is<ArrayObject>())
         srcSize = sizeof(ObjectImpl);
     js_memcpy(dst, src, srcSize);
     tenuredSize += moveSlotsToTenured(dst, src, dstKind);
     tenuredSize += moveElementsToTenured(dst, src, dstKind);
     if (src->is<TypedArrayObject>())
         forwardTypedArrayPointers(dst, src);
     /* The shape's list head may point into the old object. */
     if (&src->shape_ == dst->shape_->listp)
         dst->shape_->listp = &dst->shape_;
     return tenuredSize;
 }
 void
 js::Nursery::forwardTypedArrayPointers(JSObject *dst, JSObject *src)
 {
     /*
      * Typed array data may be stored inline inside the object's fixed slots. If
      * so, we need update the private pointer and leave a forwarding pointer at
      * the start of the data.
      */
     TypedArrayObject &typedArray = src->as<TypedArrayObject>();
     JS_ASSERT_IF(typedArray.buffer(), !isInside(src->getPrivate()));
     if (typedArray.buffer())
         return;
     void *srcData = src->fixedData(TypedArrayObject::FIXED_DATA_START);
     void *dstData = dst->fixedData(TypedArrayObject::FIXED_DATA_START);
     JS_ASSERT(src->getPrivate() == srcData);
     dst->setPrivate(dstData);
     /*
      * We don't know the number of slots here, but
      * TypedArrayObject::AllocKindForLazyBuffer ensures that it's always at
      * least one.
      */
     size_t nslots = 1;
     setSlotsForwardingPointer(reinterpret_cast<HeapSlot*>(srcData),
                               reinterpret_cast<HeapSlot*>(dstData),
                               nslots);
 }
 size_t
 js::Nursery::moveSlotsToTenured(JSObject *dst, JSObject *src, AllocKind dstKind)
 {
     /* Fixed slots have already been copied over. */
     if (!src->hasDynamicSlots())
         return 0;
     if (!isInside(src->slots)) {
         hugeSlots.remove(src->slots);
         return 0;
     }
     Zone *zone = src->zone();
     size_t count = src->numDynamicSlots();
     dst->slots = zone->pod_malloc<HeapSlot>(count);
     if (!dst->slots)
         CrashAtUnhandlableOOM("Failed to allocate slots while tenuring.");
     PodCopy(dst->slots, src->slots, count);
     setSlotsForwardingPointer(src->slots, dst->slots, count);
     return count * sizeof(HeapSlot);
 }
 size_t
 js::Nursery::moveElementsToTenured(JSObject *dst, JSObject *src, AllocKind dstKind)
 {
     if (src->hasEmptyElements())
         return 0;
     Zone *zone = src->zone();
     ObjectElements *srcHeader = src->getElementsHeader();
     ObjectElements *dstHeader;
     /* TODO Bug 874151: Prefer to put element data inline if we have space. */
     if (!isInside(srcHeader)) {
         JS_ASSERT(src->elements == dst->elements);
         hugeSlots.remove(reinterpret_cast<HeapSlot*>(srcHeader));
         return 0;
     }
     size_t nslots = ObjectElements::VALUES_PER_HEADER + srcHeader->capacity;
     /* Unlike other objects, Arrays can have fixed elements. */
     if (src->is<ArrayObject>() && nslots <= GetGCKindSlots(dstKind)) {
         dst->setFixedElements();
         dstHeader = dst->getElementsHeader();
         js_memcpy(dstHeader, srcHeader, nslots * sizeof(HeapSlot));
         setElementsForwardingPointer(srcHeader, dstHeader, nslots);
         return nslots * sizeof(HeapSlot);
     }
     JS_ASSERT(nslots >= 2);
     size_t nbytes = nslots * sizeof(HeapValue);
     dstHeader = static_cast<ObjectElements *>(zone->malloc_(nbytes));
     if (!dstHeader)
         CrashAtUnhandlableOOM("Failed to allocate elements while tenuring.");
     js_memcpy(dstHeader, srcHeader, nslots * sizeof(HeapSlot));
     setElementsForwardingPointer(srcHeader, dstHeader, nslots);
     dst->elements = dstHeader->elements();
     return nslots * sizeof(HeapSlot);
 }
 static bool
 ShouldMoveToTenured(MinorCollectionTracer *trc, void **thingp)
 {
     Cell *cell = static_cast<Cell *>(*thingp);
     Nursery &nursery = *trc->nursery;
     return !nursery.isInside(thingp) && nursery.isInside(cell) &&
            !nursery.getForwardedPointer(thingp);
 }
 /* static */ void
 js::Nursery::MinorGCCallback(JSTracer *jstrc, void **thingp, JSGCTraceKind kind)
 {
     MinorCollectionTracer *trc = static_cast<MinorCollectionTracer *>(jstrc);
     if (ShouldMoveToTenured(trc, thingp))
         *thingp = trc->nursery->moveToTenured(trc, static_cast<JSObject *>(*thingp));
 }
 static void
 CheckHashTablesAfterMovingGC(JSRuntime *rt)
 {
 #ifdef JS_GC_ZEAL
     if (rt->gcZeal() == ZealCheckHashTablesOnMinorGC) {
         /* Check that internal hash tables no longer have any pointers into the nursery. */
         for (CompartmentsIter c(rt, SkipAtoms); !c.done(); c.next()) {
             c->checkNewTypeObjectTableAfterMovingGC();
             c->checkInitialShapesTableAfterMovingGC();
             c->checkWrapperMapAfterMovingGC();
             if (c->debugScopes)
                 c->debugScopes->checkHashTablesAfterMovingGC(rt);
         }
     }
 #endif
 }
 #ifdef PROFILE_NURSERY
 #define TIME_START(name) int64_t timstampStart_##name = PRMJ_Now()
 #define TIME_END(name) int64_t timstampEnd_##name = PRMJ_Now()
 #define TIME_TOTAL(name) (timstampEnd_##name - timstampStart_##name)
 #else
 #define TIME_START(name)
 #define TIME_END(name)
 #define TIME_TOTAL(name)
 #endif
 void
 js::Nursery::collect(JSRuntime *rt, JS::gcreason::Reason reason, TypeObjectList *pretenureTypes)
 {
     JS_AbortIfWrongThread(rt);
     if (rt->mainThread.suppressGC)
         return;
     if (!isEnabled())
         return;
     if (isEmpty())
         return;
     rt->gcStats.count(gcstats::STAT_MINOR_GC);
     TIME_START(total);
     AutoStopVerifyingBarriers av(rt, false);
     // Move objects pointed to by roots from the nursery to the major heap.
     MinorCollectionTracer trc(rt, this);
     // Mark the store buffer. This must happen first.
     StoreBuffer &sb = rt->gcStoreBuffer;
     TIME_START(markValues);
     sb.markValues(&trc);
     TIME_END(markValues);
     TIME_START(markCells);
     sb.markCells(&trc);
     TIME_END(markCells);
     TIME_START(markSlots);
     sb.markSlots(&trc);
     TIME_END(markSlots);
     TIME_START(markWholeCells);
     sb.markWholeCells(&trc);
     TIME_END(markWholeCells);
     TIME_START(markRelocatableValues);
     sb.markRelocatableValues(&trc);
     TIME_END(markRelocatableValues);
     TIME_START(markRelocatableCells);
     sb.markRelocatableCells(&trc);
     TIME_END(markRelocatableCells);
     TIME_START(markGenericEntries);
     sb.markGenericEntries(&trc);
     TIME_END(markGenericEntries);
     TIME_START(checkHashTables);
     CheckHashTablesAfterMovingGC(rt);
     TIME_END(checkHashTables);
     TIME_START(markRuntime);
     MarkRuntime(&trc);
     TIME_END(markRuntime);
     TIME_START(markDebugger);
     Debugger::markAll(&trc);
     TIME_END(markDebugger);
     TIME_START(clearNewObjectCache);
     rt->newObjectCache.clearNurseryObjects(rt);
     TIME_END(clearNewObjectCache);
     // Most of the work is done here. This loop iterates over objects that have
     // been moved to the major heap. If these objects have any outgoing pointers
     // to the nursery, then those nursery objects get moved as well, until no
     // objects are left to move. That is, we iterate to a fixed point.
     TIME_START(collectToFP);
     TenureCountCache tenureCounts;
     collectToFixedPoint(&trc, tenureCounts);
     TIME_END(collectToFP);
     // Update the array buffer object's view lists.
     TIME_START(sweepArrayBufferViewList);
     for (CompartmentsIter c(rt, SkipAtoms); !c.done(); c.next()) {
         if (!c->gcLiveArrayBuffers.empty())
             ArrayBufferObject::sweep(c);
     }
     TIME_END(sweepArrayBufferViewList);
     // Update any slot or element pointers whose destination has been tenured.
     TIME_START(updateJitActivations);
 #ifdef JS_ION
     js::jit::UpdateJitActivationsForMinorGC(rt, &trc);
 #endif
     TIME_END(updateJitActivations);
     // Resize the nursery.
     TIME_START(resize);
     double promotionRate = trc.tenuredSize / double(allocationEnd() - start());
     if (promotionRate > 0.05)
         growAllocableSpace();
     else if (promotionRate < 0.01)
         shrinkAllocableSpace();
     TIME_END(resize);
     // If we are promoting the nursery, or exhausted the store buffer with
     // pointers to nursery things, which will force a collection well before
     // the nursery is full, look for object types that are getting promoted
     // excessively and try to pretenure them.
     TIME_START(pretenure);
     if (pretenureTypes && (promotionRate > 0.8 || reason == JS::gcreason::FULL_STORE_BUFFER)) {
         for (size_t i = 0; i < ArrayLength(tenureCounts.entries); i++) {
             const TenureCount &entry = tenureCounts.entries[i];
             if (entry.count >= 3000)
                 pretenureTypes->append(entry.type); // ignore alloc failure
         }
     }
     TIME_END(pretenure);
     // Sweep.
     TIME_START(freeHugeSlots);
     freeHugeSlots(rt);
     TIME_END(freeHugeSlots);
     TIME_START(sweep);
     sweep(rt);
     TIME_END(sweep);
     TIME_START(clearStoreBuffer);
     rt->gcStoreBuffer.clear();
     TIME_END(clearStoreBuffer);
     // We ignore gcMaxBytes when allocating for minor collection. However, if we
     // overflowed, we disable the nursery. The next time we allocate, we'll fail
     // because gcBytes >= gcMaxBytes.
     if (rt->gcBytes >= rt->gcMaxBytes)
         disable();
     TIME_END(total);
 #ifdef PROFILE_NURSERY
     int64_t totalTime = TIME_TOTAL(total);
     if (totalTime >= GCReportThreshold) {
         static bool printedHeader = false;
         if (!printedHeader) {
             fprintf(stderr,
                     "MinorGC: Reason               PRate  Size Time   mkVals mkClls mkSlts mkWCll mkRVal mkRCll mkGnrc ckTbls mkRntm mkDbgr clrNOC collct swpABO updtIn resize pretnr frSlts clrSB  sweep\n");
             printedHeader = true;
         }
 #define FMT " %6" PRIu64
         fprintf(stderr,
                 "MinorGC: %20s %5.1f%% %4d" FMT FMT FMT FMT FMT FMT FMT FMT FMT FMT FMT FMT FMT FMT FMT FMT FMT FMT FMT FMT "\n",
                 js::gcstats::ExplainReason(reason),
                 promotionRate * 100,
                 numActiveChunks_,
                 totalTime,
                 TIME_TOTAL(markValues),
                 TIME_TOTAL(markCells),
                 TIME_TOTAL(markSlots),
                 TIME_TOTAL(markWholeCells),
                 TIME_TOTAL(markRelocatableValues),
                 TIME_TOTAL(markRelocatableCells),
                 TIME_TOTAL(markGenericEntries),
                 TIME_TOTAL(checkHashTables),
                 TIME_TOTAL(markRuntime),
                 TIME_TOTAL(markDebugger),
                 TIME_TOTAL(clearNewObjectCache),
                 TIME_TOTAL(collectToFP),
                 TIME_TOTAL(sweepArrayBufferViewList),
                 TIME_TOTAL(updateJitActivations),
                 TIME_TOTAL(resize),
                 TIME_TOTAL(pretenure),
                 TIME_TOTAL(freeHugeSlots),
                 TIME_TOTAL(clearStoreBuffer),
                 TIME_TOTAL(sweep));
 #undef FMT
     }
 #endif
 }
 void
 js::Nursery::freeHugeSlots(JSRuntime *rt)
 {
     for (HugeSlotsSet::Range r = hugeSlots.all(); !r.empty(); r.popFront())
         rt->defaultFreeOp()->free_(r.front());
     hugeSlots.clear();
 }
 void
 js::Nursery::sweep(JSRuntime *rt)
 {
 #ifdef JS_GC_ZEAL
     /* Poison the nursery contents so touching a freed object will crash. */
     JS_POISON((void *)start(), JS_SWEPT_NURSERY_PATTERN, NurserySize);
     for (int i = 0; i < NumNurseryChunks; ++i)
         initChunk(i);
     if (rt->gcZeal_ == ZealGenerationalGCValue) {
         MOZ_ASSERT(numActiveChunks_ == NumNurseryChunks);
         /* Only reset the alloc point when we are close to the end. */
         if (currentChunk_ + 1 == NumNurseryChunks)
             setCurrentChunk(0);
     } else
 #endif
     {
 #ifdef JS_CRASH_DIAGNOSTICS
         JS_POISON((void *)start(), JS_SWEPT_NURSERY_PATTERN, allocationEnd() - start());
         for (int i = 0; i < numActiveChunks_; ++i)
             chunk(i).trailer.runtime = runtime();
 #endif
         setCurrentChunk(0);
     }
     /* Set current start position for isEmpty checks. */
     currentStart_ = position();
 }
 void
 js::Nursery::growAllocableSpace()
 {
 #ifdef JS_GC_ZEAL
     MOZ_ASSERT_IF(runtime()->gcZeal_ == ZealGenerationalGCValue, numActiveChunks_ == NumNurseryChunks);
 #endif
     numActiveChunks_ = Min(numActiveChunks_ * 2, NumNurseryChunks);
 }
 void
 js::Nursery::shrinkAllocableSpace()
 {
 #ifdef JS_GC_ZEAL
     if (runtime()->gcZeal_ == ZealGenerationalGCValue)
         return;
 #endif
     numActiveChunks_ = Max(numActiveChunks_ - 1, 1);
     updateDecommittedRegion();
 }
 #endif /* JSGC_GENERATIONAL */

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js/src/gc/Nursery.cpp@b8a032363ba2 (annotated)

js/src/gc/Nursery.cpp