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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sw=2 et tw=80:
*
* 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,
#include "gc/Pretenuring.h"
#include "mozilla/Sprintf.h"
#include "gc/GCInternals.h"
#include "gc/PublicIterators.h"
#include "jit/Invalidation.h"
#include "js/Prefs.h"
#include "gc/PrivateIterators-inl.h"
#include "vm/JSScript-inl.h"
using namespace js;
using namespace js::gc;
// The number of nursery allocations at which to pay attention to an allocation
// site. This must be large enough to ensure we have enough information to infer
// the lifetime and also large enough to avoid pretenuring low volume allocation
// sites.
static constexpr size_t NormalSiteAttentionThreshold = 500;
static constexpr size_t UnknownSiteAttentionThreshold = 30000;
// The maximum number of alloc sites to create between each minor
// collection. Stop tracking allocation after this limit is reached. This
// prevents unbounded time traversing the list during minor GC.
static constexpr size_t MaxAllocSitesPerMinorGC = 500;
// The maximum number of times to invalidate JIT code for a site. After this we
// leave the site's state as Unknown and don't pretenure allocations.
// Note we use 4 bits to store the invalidation count.
static constexpr size_t MaxInvalidationCount = 5;
// The minimum number of allocated cells needed to determine the survival rate
// of cells in newly created arenas.
static constexpr size_t MinCellsRequiredForSurvivalRate = 100;
// The young survival rate below which a major collection is determined to have
// a low young survival rate.
static constexpr double LowYoungSurvivalThreshold = 0.05;
// The number of consecutive major collections with a low young survival rate
// that must occur before recovery is attempted.
static constexpr size_t LowYoungSurvivalCountBeforeRecovery = 2;
// The proportion of the nursery that must be promoted above which a minor
// collection may be determined to have a high nursery survival rate.
static constexpr double HighNurserySurvivalPromotionThreshold = 0.6;
// The number of nursery allocations made by optimized JIT code that must be
// promoted above which a minor collection may be determined to have a high
// nursery survival rate.
static constexpr size_t HighNurserySurvivalOptimizedAllocThreshold = 10000;
// The number of consecutive minor collections with a high nursery survival rate
// that must occur before recovery is attempted.
static constexpr size_t HighNurserySurvivalCountBeforeRecovery = 2;
AllocSite* const AllocSite::EndSentinel = reinterpret_cast<AllocSite*>(1);
JSScript* const AllocSite::WasmScript =
reinterpret_cast<JSScript*>(AllocSite::STATE_MASK + 1);
bool PretenuringNursery::canCreateAllocSite() {
MOZ_ASSERT(allocSitesCreated <= MaxAllocSitesPerMinorGC);
return JS::Prefs::site_based_pretenuring() &&
allocSitesCreated < MaxAllocSitesPerMinorGC;
}
size_t PretenuringNursery::doPretenuring(GCRuntime* gc, JS::GCReason reason,
bool validPromotionRate,
double promotionRate, bool reportInfo,
size_t reportThreshold) {
size_t sitesActive = 0;
size_t sitesPretenured = 0;
size_t sitesInvalidated = 0;
size_t zonesWithHighNurserySurvival = 0;
// Zero allocation counts.
totalAllocCount_ = 0;
for (ZonesIter zone(gc, SkipAtoms); !zone.done(); zone.next()) {
for (auto& count : zone->pretenuring.nurseryAllocCounts) {
count = 0;
}
}
// Check whether previously optimized code has changed its behaviour and
// needs to be recompiled so that it can pretenure its allocations.
if (validPromotionRate) {
for (ZonesIter zone(gc, SkipAtoms); !zone.done(); zone.next()) {
bool highNurserySurvivalRate =
promotionRate > HighNurserySurvivalPromotionThreshold &&
zone->optimizedAllocSite()->nurseryPromotedCount >=
HighNurserySurvivalOptimizedAllocThreshold;
zone->pretenuring.noteHighNurserySurvivalRate(highNurserySurvivalRate);
if (highNurserySurvivalRate) {
zonesWithHighNurserySurvival++;
}
}
}
if (reportInfo) {
AllocSite::printInfoHeader(reason, promotionRate);
}
AllocSite* site = allocatedSites;
allocatedSites = AllocSite::EndSentinel;
while (site != AllocSite::EndSentinel) {
AllocSite* next = site->nextNurseryAllocated;
site->nextNurseryAllocated = nullptr;
if (site->isNormal()) {
sitesActive++;
updateTotalAllocCounts(site);
auto result = site->processSite(gc, NormalSiteAttentionThreshold,
reportInfo, reportThreshold);
if (result == AllocSite::WasPretenured ||
result == AllocSite::WasPretenuredAndInvalidated) {
sitesPretenured++;
if (site->hasScript()) {
site->script()->realm()->numAllocSitesPretenured++;
}
}
if (result == AllocSite::WasPretenuredAndInvalidated) {
sitesInvalidated++;
}
}
site = next;
}
// Catch-all sites don't end up on the list if they are only used from
// optimized JIT code, so process them here.
for (ZonesIter zone(gc, SkipAtoms); !zone.done(); zone.next()) {
for (auto& site : zone->pretenuring.unknownAllocSites) {
updateTotalAllocCounts(&site);
if (site.traceKind() == JS::TraceKind::Object) {
site.processCatchAllSite(reportInfo, reportThreshold);
} else {
site.processSite(gc, UnknownSiteAttentionThreshold, reportInfo,
reportThreshold);
}
// Result checked in Nursery::doPretenuring.
}
updateTotalAllocCounts(zone->optimizedAllocSite());
zone->optimizedAllocSite()->processCatchAllSite(reportInfo,
reportThreshold);
// The data from the promoted alloc sites is never used so clear them here.
for (AllocSite& site : zone->pretenuring.promotedAllocSites) {
site.resetNurseryAllocations();
}
}
if (reportInfo) {
AllocSite::printInfoFooter(allocSitesCreated, sitesActive, sitesPretenured,
sitesInvalidated);
if (zonesWithHighNurserySurvival) {
fprintf(stderr, " %zu zones with high nursery survival rate\n",
zonesWithHighNurserySurvival);
}
}
allocSitesCreated = 0;
return sitesPretenured;
}
AllocSite::SiteResult AllocSite::processSite(GCRuntime* gc,
size_t attentionThreshold,
bool reportInfo,
size_t reportThreshold) {
MOZ_ASSERT(kind() != Kind::Optimized);
MOZ_ASSERT(nurseryAllocCount >= nurseryPromotedCount);
SiteResult result = NoChange;
bool hasPromotionRate = false;
double promotionRate = 0.0;
bool wasInvalidated = false;
if (nurseryAllocCount > attentionThreshold) {
promotionRate = double(nurseryPromotedCount) / double(nurseryAllocCount);
hasPromotionRate = true;
AllocSite::State prevState = state();
updateStateOnMinorGC(promotionRate);
AllocSite::State newState = state();
if (prevState == AllocSite::State::Unknown &&
newState == AllocSite::State::LongLived) {
result = WasPretenured;
// We can optimize JIT code before we realise that a site should be
// pretenured. Make sure we invalidate any existing optimized code.
if (hasScript()) {
wasInvalidated = invalidateScript(gc);
if (wasInvalidated) {
result = WasPretenuredAndInvalidated;
}
}
}
}
if (reportInfo && allocCount() >= reportThreshold) {
printInfo(hasPromotionRate, promotionRate, wasInvalidated);
}
resetNurseryAllocations();
return result;
}
void AllocSite::processCatchAllSite(bool reportInfo, size_t reportThreshold) {
MOZ_ASSERT(!isNormal());
if (!hasNurseryAllocations()) {
return;
}
if (reportInfo && allocCount() >= reportThreshold) {
printInfo(false, 0.0, false);
}
resetNurseryAllocations();
}
void PretenuringNursery::updateTotalAllocCounts(AllocSite* site) {
JS::TraceKind kind = site->traceKind();
totalAllocCount_ += site->nurseryAllocCount;
PretenuringZone& zone = site->zone()->pretenuring;
zone.nurseryAllocCount(kind) += site->nurseryAllocCount;
}
bool AllocSite::invalidateScript(GCRuntime* gc) {
CancelOffThreadIonCompile(script());
if (!script()->hasIonScript()) {
return false;
}
if (invalidationLimitReached()) {
MOZ_ASSERT(state() == State::Unknown);
return false;
}
invalidationCount++;
if (invalidationLimitReached()) {
setState(State::Unknown);
}
JSContext* cx = gc->rt->mainContextFromOwnThread();
jit::Invalidate(cx, script(),
/* resetUses = */ false,
/* cancelOffThread = */ true);
return true;
}
bool AllocSite::invalidationLimitReached() const {
MOZ_ASSERT(invalidationCount <= MaxInvalidationCount);
return invalidationCount == MaxInvalidationCount;
}
void PretenuringNursery::maybeStopPretenuring(GCRuntime* gc) {
for (GCZonesIter zone(gc); !zone.done(); zone.next()) {
double rate;
if (zone->pretenuring.calculateYoungTenuredSurvivalRate(&rate)) {
bool lowYoungSurvivalRate = rate < LowYoungSurvivalThreshold;
zone->pretenuring.noteLowYoungTenuredSurvivalRate(lowYoungSurvivalRate);
}
}
}
AllocSite::Kind AllocSite::kind() const {
if (isNormal()) {
return Kind::Normal;
}
if (this == zone()->optimizedAllocSite()) {
return Kind::Optimized;
}
MOZ_ASSERT(this == zone()->unknownAllocSite(traceKind()));
return Kind::Unknown;
}
void AllocSite::updateStateOnMinorGC(double promotionRate) {
// The state changes based on whether the promotion rate is deemed high
// (greater that 90%):
//
// high high
// ------------------> ------------------>
// ShortLived Unknown LongLived
// <------------------ <------------------
// !high !high
//
// The nursery is used to allocate if the site's state is Unknown or
// ShortLived. There are no direct transition between ShortLived and LongLived
// to avoid pretenuring sites that we've recently observed being short-lived.
if (invalidationLimitReached()) {
MOZ_ASSERT(state() == State::Unknown);
return;
}
bool highPromotionRate = promotionRate >= 0.9;
switch (state()) {
case State::Unknown:
if (highPromotionRate) {
setState(State::LongLived);
} else {
setState(State::ShortLived);
}
break;
case State::ShortLived: {
if (highPromotionRate) {
setState(State::Unknown);
}
break;
}
case State::LongLived: {
if (!highPromotionRate) {
setState(State::Unknown);
}
break;
}
}
}
bool AllocSite::maybeResetState() {
if (invalidationLimitReached()) {
MOZ_ASSERT(state() == State::Unknown);
return false;
}
invalidationCount++;
setState(State::Unknown);
return true;
}
void AllocSite::trace(JSTracer* trc) {
if (hasScript()) {
JSScript* s = script();
TraceManuallyBarrieredEdge(trc, &s, "AllocSite script");
if (s != script()) {
setScript(s);
}
}
}
bool PretenuringZone::calculateYoungTenuredSurvivalRate(double* rateOut) {
MOZ_ASSERT(allocCountInNewlyCreatedArenas >=
survivorCountInNewlyCreatedArenas);
if (allocCountInNewlyCreatedArenas < MinCellsRequiredForSurvivalRate) {
return false;
}
*rateOut = double(survivorCountInNewlyCreatedArenas) /
double(allocCountInNewlyCreatedArenas);
return true;
}
void PretenuringZone::noteLowYoungTenuredSurvivalRate(
bool lowYoungSurvivalRate) {
if (lowYoungSurvivalRate) {
lowYoungTenuredSurvivalCount++;
} else {
lowYoungTenuredSurvivalCount = 0;
}
}
void PretenuringZone::noteHighNurserySurvivalRate(
bool highNurserySurvivalRate) {
if (highNurserySurvivalRate) {
highNurserySurvivalCount++;
} else {
highNurserySurvivalCount = 0;
}
}
bool PretenuringZone::shouldResetNurseryAllocSites() {
bool shouldReset =
highNurserySurvivalCount >= HighNurserySurvivalCountBeforeRecovery;
if (shouldReset) {
highNurserySurvivalCount = 0;
}
return shouldReset;
}
bool PretenuringZone::shouldResetPretenuredAllocSites() {
bool shouldReset =
lowYoungTenuredSurvivalCount >= LowYoungSurvivalCountBeforeRecovery;
if (shouldReset) {
lowYoungTenuredSurvivalCount = 0;
}
return shouldReset;
}
/* static */
void AllocSite::printInfoHeader(JS::GCReason reason, double promotionRate) {
fprintf(stderr, " %-16s %-16s %-20s %-8s %-8s %-6s %-10s\n", "site", "zone",
"script/kind", "nallocs", "promotes", "prate", "state");
}
/* static */
void AllocSite::printInfoFooter(size_t sitesCreated, size_t sitesActive,
size_t sitesPretenured,
size_t sitesInvalidated) {
fprintf(stderr,
" %zu alloc sites created, %zu active, %zu pretenured, %zu "
"invalidated\n",
sitesCreated, sitesActive, sitesPretenured, sitesInvalidated);
}
static const char* AllocSiteKindName(AllocSite::Kind kind) {
switch (kind) {
case AllocSite::Kind::Normal:
return "normal";
case AllocSite::Kind::Unknown:
return "unknown";
case AllocSite::Kind::Optimized:
return "optimized";
default:
MOZ_CRASH("Bad AllocSite kind");
}
}
void AllocSite::printInfo(bool hasPromotionRate, double promotionRate,
bool wasInvalidated) const {
// Zone.
fprintf(stderr, " %16p %16p", this, zone());
// Script, or which kind of catch-all site this is.
if (!hasScript()) {
const char* siteKindName = AllocSiteKindName(kind());
if (kind() == Kind::Unknown) {
char buffer[32];
const char* traceKindName = JS::GCTraceKindToAscii(traceKind());
SprintfLiteral(buffer, "%s %s", siteKindName, traceKindName);
fprintf(stderr, " %-20s", buffer);
} else {
fprintf(stderr, " %-20s", siteKindName);
}
} else {
fprintf(stderr, " %20p", script());
}
// Nursery allocation count, missing for optimized sites.
char buffer[16] = {'\0'};
if (kind() != Kind::Optimized) {
SprintfLiteral(buffer, "%8" PRIu32, nurseryAllocCount);
}
fprintf(stderr, " %8s", buffer);
// Nursery promotion count.
fprintf(stderr, " %8" PRIu32, nurseryPromotedCount);
// Promotion rate, if there were enough allocations.
buffer[0] = '\0';
if (hasPromotionRate) {
SprintfLiteral(buffer, "%5.1f%%", std::min(1.0, promotionRate) * 100);
}
fprintf(stderr, " %6s", buffer);
// Current state where applicable.
const char* state = kind() != Kind::Optimized ? stateName() : "";
fprintf(stderr, " %-10s", state);
// Whether the associated script was invalidated.
if (wasInvalidated) {
fprintf(stderr, " invalidated");
}
fprintf(stderr, "\n");
}
const char* AllocSite::stateName() const {
switch (state()) {
case State::ShortLived:
return "ShortLived";
case State::Unknown:
return "Unknown";
case State::LongLived:
return "LongLived";
}
MOZ_CRASH("Unknown state");
}