Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 459 insertions, 0 deletions

diff --git a/js/src/gc/Pretenuring.cpp b/js/src/gc/Pretenuring.cpp
new file mode 100644
index 0000000000..5703663e47
--- /dev/null
+++ b/js/src/gc/Pretenuring.cpp
@@ -0,0 +1,459 @@
+/* -*- 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,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "gc/Pretenuring.h"
+
+#include "mozilla/Sprintf.h"
+
+#include "gc/GCInternals.h"
+#include "gc/PublicIterators.h"
+#include "jit/Invalidation.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 AllocSiteAttentionThreshold = 500;
+
+// 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 tenured 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
+// tenured 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);
+
+static bool SiteBasedPretenuringEnabled = true;
+
+JS_PUBLIC_API void JS::SetSiteBasedPretenuringEnabled(bool enable) {
+  SiteBasedPretenuringEnabled = enable;
+}
+
+bool PretenuringNursery::canCreateAllocSite() {
+  MOZ_ASSERT(allocSitesCreated <= MaxAllocSitesPerMinorGC);
+  return SiteBasedPretenuringEnabled &&
+         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()->nurseryTenuredCount >=
+              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;
+
+    MOZ_ASSERT_IF(site->isNormal(),
+                  site->nurseryAllocCount >= site->nurseryTenuredCount);
+
+    if (site->isNormal()) {
+      processSite(gc, site, sitesActive, sitesPretenured, sitesInvalidated,
+                  reportInfo, reportThreshold);
+    }
+
+    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) {
+      processCatchAllSite(&site, reportInfo, reportThreshold);
+    }
+    processCatchAllSite(zone->optimizedAllocSite(), reportInfo,
+                        reportThreshold);
+  }
+
+  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;
+}
+
+void PretenuringNursery::processSite(GCRuntime* gc, AllocSite* site,
+                                     size_t& sitesActive,
+                                     size_t& sitesPretenured,
+                                     size_t& sitesInvalidated, bool reportInfo,
+                                     size_t reportThreshold) {
+  sitesActive++;
+
+  updateAllocCounts(site);
+
+  bool hasPromotionRate = false;
+  double promotionRate = 0.0;
+  bool wasInvalidated = false;
+  if (site->nurseryAllocCount > AllocSiteAttentionThreshold) {
+    promotionRate =
+        double(site->nurseryTenuredCount) / double(site->nurseryAllocCount);
+    hasPromotionRate = true;
+
+    AllocSite::State prevState = site->state();
+    site->updateStateOnMinorGC(promotionRate);
+    AllocSite::State newState = site->state();
+
+    if (prevState == AllocSite::State::Unknown &&
+        newState == AllocSite::State::LongLived) {
+      sitesPretenured++;
+
+      // We can optimize JIT code before we realise that a site should be
+      // pretenured. Make sure we invalidate any existing optimized code.
+      if (site->hasScript()) {
+        wasInvalidated = site->invalidateScript(gc);
+        if (wasInvalidated) {
+          sitesInvalidated++;
+        }
+      }
+    }
+  }
+
+  if (reportInfo && site->allocCount() >= reportThreshold) {
+    site->printInfo(hasPromotionRate, promotionRate, wasInvalidated);
+  }
+
+  site->resetNurseryAllocations();
+}
+
+void PretenuringNursery::processCatchAllSite(AllocSite* site, bool reportInfo,
+                                             size_t reportThreshold) {
+  if (!site->hasNurseryAllocations()) {
+    return;
+  }
+
+  updateAllocCounts(site);
+
+  if (reportInfo && site->allocCount() >= reportThreshold) {
+    site->printInfo(false, 0.0, false);
+  }
+
+  site->resetNurseryAllocations();
+}
+
+void PretenuringNursery::updateAllocCounts(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 (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,
+          "Pretenuring info after %s minor GC with %4.1f%% promotion rate:\n",
+          ExplainGCReason(reason), promotionRate * 100.0);
+}
+
+/* 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);
+}
+
+void AllocSite::printInfo(bool hasPromotionRate, double promotionRate,
+                          bool wasInvalidated) const {
+  // Zone.
+  fprintf(stderr, "  %p %p", this, zone());
+
+  // Script, or which kind of catch-all site this is.
+  if (!hasScript()) {
+    fprintf(stderr, " %16s",
+            kind() == Kind::Optimized
+                ? "optimized"
+                : (kind() == Kind::Normal ? "normal" : "unknown"));
+  } else {
+    fprintf(stderr, " %16p", 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 tenure count.
+  fprintf(stderr, " %8" PRIu32, nurseryTenuredCount);
+
+  // 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 for sites associated with a script.
+  const char* state = isNormal() ? 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");
+}