Commit 778a486d authored by Paul Bone's avatar Paul Bone
Browse files

Bug 1392511 - Report the correct information for used bytes. r=jonco 

Only use the promotion rate to make pre tenuring and nursery size decisions
(now that it is calculated correctly and not under-estimated) if the nursery
is at least 90% full.
parent a1f7ac50

js/src/gc/Nursery.cpp

+47 −23
Original line number Diff line number Diff line
@@ -465,6 +465,22 @@ js::TenuringTracer::TenuringTracer(JSRuntime* rt, Nursery* nursery) 
{

}



inline float

js::Nursery::calcPromotionRate(bool *validForTenuring) const {

    float used = float(previousGC.nurseryUsedBytes);

    float capacity = float(previousGC.nurseryCapacity);

    float tenured = float(previousGC.tenuredBytes);



    if (validForTenuring) {

        /*

         * We can only use promotion rates if they're likely to be valid,

         * they're only valid if the nursury was at least 90% full.

         */

        *validForTenuring = used > capacity * 0.9f;

    }

    return tenured / used;

}



void

js::Nursery::renderProfileJSON(JSONPrinter& json) const

{
@@ -490,8 +506,7 @@ js::Nursery::renderProfileJSON(JSONPrinter& json) const 


    json.property("reason", JS::gcreason::ExplainReason(previousGC.reason));

    json.property("bytes_tenured", previousGC.tenuredBytes);

    json.floatProperty("promotion_rate",

                       100.0 * previousGC.tenuredBytes / double(previousGC.nurseryUsedBytes), 2);

    json.floatProperty("promotion_rate", calcPromotionRate(nullptr), 0);

    json.property("nursery_bytes", previousGC.nurseryUsedBytes);

    json.property("new_nursery_bytes", numChunks() * ChunkSize);
@@ -609,14 +624,13 @@ js::Nursery::collect(JS::gcreason::Reason reason) 
    JS::AutoSuppressGCAnalysis nogc;



    TenureCountCache tenureCounts;

    double promotionRate = 0;

    previousGC.reason = JS::gcreason::NO_REASON;

    if (!isEmpty())

        promotionRate = doCollection(reason, tenureCounts);

        doCollection(reason, tenureCounts);



    // Resize the nursery.

    startProfile(ProfileKey::Resize);

    maybeResizeNursery(reason, promotionRate);

    maybeResizeNursery(reason);

    endProfile(ProfileKey::Resize);



    // If we are promoting the nursery, or exhausted the store buffer with
@@ -624,7 +638,10 @@ js::Nursery::collect(JS::gcreason::Reason reason) 
    // the nursery is full, look for object groups that are getting promoted

    // excessively and try to pretenure them.

    startProfile(ProfileKey::Pretenure);

    bool validPromotionRate;

    const float promotionRate = calcPromotionRate(&validPromotionRate);

    uint32_t pretenureCount = 0;

    if (validPromotionRate) {

        if (promotionRate > 0.8 || IsFullStoreBufferReason(reason)) {

            JSContext* cx = TlsContext.get();

            for (auto& entry : tenureCounts.entries) {
@@ -638,6 +655,7 @@ js::Nursery::collect(JS::gcreason::Reason reason) 
                }

            }

        }

    }

    endProfile(ProfileKey::Pretenure);



    // We ignore gcMaxBytes when allocating for minor collection. However, if we
@@ -685,7 +703,7 @@ js::Nursery::collect(JS::gcreason::Reason reason) 
    }

}



double

void

js::Nursery::doCollection(JS::gcreason::Reason reason,

                          TenureCountCache& tenureCounts)

{
@@ -696,7 +714,8 @@ js::Nursery::doCollection(JS::gcreason::Reason reason, 
    AutoDisableProxyCheck disableStrictProxyChecking;

    mozilla::DebugOnly<AutoEnterOOMUnsafeRegion> oomUnsafeRegion;



    size_t initialNurserySize = spaceToEnd();

    const size_t initialNurseryCapacity = spaceToEnd();

    const size_t initialNurseryUsedBytes = initialNurseryCapacity - freeSpace();



    // Move objects pointed to by roots from the nursery to the major heap.

    TenuringTracer mover(rt, this);
@@ -793,11 +812,9 @@ js::Nursery::doCollection(JS::gcreason::Reason reason, 
    endProfile(ProfileKey::CheckHashTables);



    previousGC.reason = reason;

    previousGC.nurseryUsedBytes = initialNurserySize;

    previousGC.nurseryCapacity = initialNurseryCapacity;

    previousGC.nurseryUsedBytes = initialNurseryUsedBytes;

    previousGC.tenuredBytes = mover.tenuredSize;



    // Calculate and return the promotion rate.

    return mover.tenuredSize / double(initialNurserySize);

}



void
@@ -923,7 +940,7 @@ js::Nursery::setStartPosition() 
}



void

js::Nursery::maybeResizeNursery(JS::gcreason::Reason reason, double promotionRate)

js::Nursery::maybeResizeNursery(JS::gcreason::Reason reason)

{

    static const double GrowThreshold   = 0.05;

    static const double ShrinkThreshold = 0.01;
@@ -942,20 +959,27 @@ js::Nursery::maybeResizeNursery(JS::gcreason::Reason reason, double promotionRat 
        return;

#endif



    bool canUsePromotionRate;

    const float promotionRate = calcPromotionRate(&canUsePromotionRate);



    newMaxNurseryChunks = runtime()->gc.tunables.gcMaxNurseryBytes() >> ChunkShift;

    if (newMaxNurseryChunks != maxNurseryChunks_) {

        maxNurseryChunks_ = newMaxNurseryChunks;

        /* The configured maximum nursery size is changing */

        int extraChunks = numChunks() - newMaxNurseryChunks;

        const int extraChunks = numChunks() - newMaxNurseryChunks;

        if (extraChunks > 0) {

            /* We need to shrink the nursery */

            shrinkAllocableSpace(extraChunks);



            if (canUsePromotionRate)

                previousPromotionRate_ = promotionRate;

            return;

        }

    }



    if (!canUsePromotionRate)

        return;



    if (promotionRate > GrowThreshold)

        growAllocableSpace();

    else if (promotionRate < ShrinkThreshold && previousPromotionRate_ < ShrinkThreshold)

js/src/gc/Nursery.h

+15 −5
Original line number Diff line number Diff line
@@ -316,7 +316,7 @@ class Nursery 
    unsigned maxNurseryChunks_;



    /* Promotion rate for the previous minor collection. */

    double previousPromotionRate_;

    float previousPromotionRate_;



    /* Report minor collections taking at least this long, if enabled. */

    mozilla::TimeDuration profileThreshold_;
@@ -355,10 +355,20 @@ class Nursery 


    struct {

        JS::gcreason::Reason reason;

        uint64_t nurseryUsedBytes;

        uint64_t tenuredBytes;

        size_t nurseryCapacity;

        size_t nurseryUsedBytes;

        size_t tenuredBytes;

    } previousGC;



    /*

     * Calculate the promotion rate of the most recent minor GC.

     * The valid_for_tenuring parameter is used to return whether this

     * promotion rate is accurate enough (the nursery was full enough) to be

     * used for tenuring and other decisions.

     */

    float

    calcPromotionRate(bool *validForTenuring) const;



    /*

     * The set of externally malloced buffers potentially kept live by objects

     * stored in the nursery. Any external buffers that do not belong to a
@@ -438,7 +448,7 @@ class Nursery 
    /* Common internal allocator function. */

    void* allocate(size_t size);



    double doCollection(JS::gcreason::Reason reason,

    void doCollection(JS::gcreason::Reason reason,

                        gc::TenureCountCache& tenureCounts);



    /*
@@ -466,7 +476,7 @@ class Nursery 
    void sweepDictionaryModeObjects();



    /* Change the allocable space provided by the nursery. */

    void maybeResizeNursery(JS::gcreason::Reason reason, double promotionRate);

    void maybeResizeNursery(JS::gcreason::Reason reason);

    void growAllocableSpace();

    void shrinkAllocableSpace(unsigned removeNumChunks);

    void minimizeAllocableSpace();