heap.cc.svn-base

Google浏览器V8内核代码

// Copyright 2006-2008 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
//       copyright notice, this list of conditions and the following
//       disclaimer in the documentation and/or other materials provided
//       with the distribution.
//     * Neither the name of Google Inc. nor the names of its
//       contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#include "v8.h"

#include "accessors.h"
#include "api.h"
#include "bootstrapper.h"
#include "codegen-inl.h"
#include "compilation-cache.h"
#include "debug.h"
#include "global-handles.h"
#include "jsregexp.h"
#include "mark-compact.h"
#include "natives.h"
#include "scanner.h"
#include "scopeinfo.h"
#include "v8threads.h"

namespace v8 { namespace internal {

#define ROOT_ALLOCATION(type, name) type* Heap::name##_;
  ROOT_LIST(ROOT_ALLOCATION)
#undef ROOT_ALLOCATION


#define STRUCT_ALLOCATION(NAME, Name, name) Map* Heap::name##_map_;
  STRUCT_LIST(STRUCT_ALLOCATION)
#undef STRUCT_ALLOCATION


#define SYMBOL_ALLOCATION(name, string) String* Heap::name##_;
  SYMBOL_LIST(SYMBOL_ALLOCATION)
#undef SYMBOL_ALLOCATION


NewSpace* Heap::new_space_ = NULL;
OldSpace* Heap::old_pointer_space_ = NULL;
OldSpace* Heap::old_data_space_ = NULL;
OldSpace* Heap::code_space_ = NULL;
MapSpace* Heap::map_space_ = NULL;
LargeObjectSpace* Heap::lo_space_ = NULL;

int Heap::promoted_space_limit_ = 0;
int Heap::old_gen_exhausted_ = false;

int Heap::amount_of_external_allocated_memory_ = 0;
int Heap::amount_of_external_allocated_memory_at_last_global_gc_ = 0;

// semispace_size_ should be a power of 2 and old_generation_size_ should be
// a multiple of Page::kPageSize.
int Heap::semispace_size_  = 1*MB;
int Heap::old_generation_size_ = 512*MB;
int Heap::initial_semispace_size_ = 256*KB;

GCCallback Heap::global_gc_prologue_callback_ = NULL;
GCCallback Heap::global_gc_epilogue_callback_ = NULL;

// Variables set based on semispace_size_ and old_generation_size_ in
// ConfigureHeap.
int Heap::young_generation_size_ = 0;  // Will be 2 * semispace_size_.

// Double the new space after this many scavenge collections.
int Heap::new_space_growth_limit_ = 8;
int Heap::scavenge_count_ = 0;
Heap::HeapState Heap::gc_state_ = NOT_IN_GC;

int Heap::mc_count_ = 0;
int Heap::gc_count_ = 0;

#ifdef DEBUG
bool Heap::allocation_allowed_ = true;

int Heap::allocation_timeout_ = 0;
bool Heap::disallow_allocation_failure_ = false;
#endif  // DEBUG


int Heap::Capacity() {
  if (!HasBeenSetup()) return 0;

  return new_space_->Capacity() +
      old_pointer_space_->Capacity() +
      old_data_space_->Capacity() +
      code_space_->Capacity() +
      map_space_->Capacity();
}


int Heap::Available() {
  if (!HasBeenSetup()) return 0;

  return new_space_->Available() +
      old_pointer_space_->Available() +
      old_data_space_->Available() +
      code_space_->Available() +
      map_space_->Available();
}


bool Heap::HasBeenSetup() {
  return new_space_ != NULL &&
         old_pointer_space_ != NULL &&
         old_data_space_ != NULL &&
         code_space_ != NULL &&
         map_space_ != NULL &&
         lo_space_ != NULL;
}


GarbageCollector Heap::SelectGarbageCollector(AllocationSpace space) {
  // Is global GC requested?
  if (space != NEW_SPACE || FLAG_gc_global) {
    Counters::gc_compactor_caused_by_request.Increment();
    return MARK_COMPACTOR;
  }

  // Is enough data promoted to justify a global GC?
  if (PromotedSpaceSize() + PromotedExternalMemorySize()
      > promoted_space_limit_) {
    Counters::gc_compactor_caused_by_promoted_data.Increment();
    return MARK_COMPACTOR;
  }

  // Have allocation in OLD and LO failed?
  if (old_gen_exhausted_) {
    Counters::gc_compactor_caused_by_oldspace_exhaustion.Increment();
    return MARK_COMPACTOR;
  }

  // Is there enough space left in OLD to guarantee that a scavenge can
  // succeed?
  //
  // Note that MemoryAllocator->MaxAvailable() undercounts the memory available
  // for object promotion. It counts only the bytes that the memory
  // allocator has not yet allocated from the OS and assigned to any space,
  // and does not count available bytes already in the old space or code
  // space.  Undercounting is safe---we may get an unrequested full GC when
  // a scavenge would have succeeded.
  if (MemoryAllocator::MaxAvailable() <= new_space_->Size()) {
    Counters::gc_compactor_caused_by_oldspace_exhaustion.Increment();
    return MARK_COMPACTOR;
  }

  // Default
  return SCAVENGER;
}


// TODO(1238405): Combine the infrastructure for --heap-stats and
// --log-gc to avoid the complicated preprocessor and flag testing.
#if defined(DEBUG) || defined(ENABLE_LOGGING_AND_PROFILING)
void Heap::ReportStatisticsBeforeGC() {
  // Heap::ReportHeapStatistics will also log NewSpace statistics when
  // compiled with ENABLE_LOGGING_AND_PROFILING and --log-gc is set.  The
  // following logic is used to avoid double logging.
#if defined(DEBUG) && defined(ENABLE_LOGGING_AND_PROFILING)
  if (FLAG_heap_stats || FLAG_log_gc) new_space_->CollectStatistics();
  if (FLAG_heap_stats) {
    ReportHeapStatistics("Before GC");
  } else if (FLAG_log_gc) {
    new_space_->ReportStatistics();
  }
  if (FLAG_heap_stats || FLAG_log_gc) new_space_->ClearHistograms();
#elif defined(DEBUG)
  if (FLAG_heap_stats) {
    new_space_->CollectStatistics();
    ReportHeapStatistics("Before GC");
    new_space_->ClearHistograms();
  }
#elif defined(ENABLE_LOGGING_AND_PROFILING)
  if (FLAG_log_gc) {
    new_space_->CollectStatistics();
    new_space_->ReportStatistics();
    new_space_->ClearHistograms();
  }
#endif
}


// TODO(1238405): Combine the infrastructure for --heap-stats and
// --log-gc to avoid the complicated preprocessor and flag testing.
void Heap::ReportStatisticsAfterGC() {
  // Similar to the before GC, we use some complicated logic to ensure that
  // NewSpace statistics are logged exactly once when --log-gc is turned on.
#if defined(DEBUG) && defined(ENABLE_LOGGING_AND_PROFILING)
  if (FLAG_heap_stats) {
    ReportHeapStatistics("After GC");
  } else if (FLAG_log_gc) {
    new_space_->ReportStatistics();
  }
#elif defined(DEBUG)
  if (FLAG_heap_stats) ReportHeapStatistics("After GC");
#elif defined(ENABLE_LOGGING_AND_PROFILING)
  if (FLAG_log_gc) new_space_->ReportStatistics();
#endif
}
#endif  // defined(DEBUG) || defined(ENABLE_LOGGING_AND_PROFILING)


void Heap::GarbageCollectionPrologue() {
  RegExpImpl::NewSpaceCollectionPrologue();
  gc_count_++;
#ifdef DEBUG
  ASSERT(allocation_allowed_ && gc_state_ == NOT_IN_GC);
  allow_allocation(false);

  if (FLAG_verify_heap) {
    Verify();
  }

  if (FLAG_gc_verbose) Print();

  if (FLAG_print_rset) {
    // Not all spaces have remembered set bits that we care about.
    old_pointer_space_->PrintRSet();
    map_space_->PrintRSet();
    lo_space_->PrintRSet();
  }
#endif

#if defined(DEBUG) || defined(ENABLE_LOGGING_AND_PROFILING)
  ReportStatisticsBeforeGC();
#endif
}

int Heap::SizeOfObjects() {
  int total = 0;
  AllSpaces spaces;
  while (Space* space = spaces.next()) total += space->Size();
  return total;
}

void Heap::GarbageCollectionEpilogue() {
#ifdef DEBUG
  allow_allocation(true);
  ZapFromSpace();

  if (FLAG_verify_heap) {
    Verify();
  }

  if (FLAG_print_global_handles) GlobalHandles::Print();
  if (FLAG_print_handles) PrintHandles();
  if (FLAG_gc_verbose) Print();
  if (FLAG_code_stats) ReportCodeStatistics("After GC");
#endif

  Counters::alive_after_last_gc.Set(SizeOfObjects());

  SymbolTable* symbol_table = SymbolTable::cast(Heap::symbol_table_);
  Counters::symbol_table_capacity.Set(symbol_table->Capacity());
  Counters::number_of_symbols.Set(symbol_table->NumberOfElements());
#if defined(DEBUG) || defined(ENABLE_LOGGING_AND_PROFILING)
  ReportStatisticsAfterGC();
#endif
}


void Heap::CollectAllGarbage() {
  // Since we are ignoring the return value, the exact choice of space does
  // not matter, so long as we do not specify NEW_SPACE, which would not
  // cause a full GC.
  CollectGarbage(0, OLD_POINTER_SPACE);
}


bool Heap::CollectGarbage(int requested_size, AllocationSpace space) {
  // The VM is in the GC state until exiting this function.
  VMState state(GC);

#ifdef DEBUG
  // Reset the allocation timeout to the GC interval, but make sure to
  // allow at least a few allocations after a collection. The reason
  // for this is that we have a lot of allocation sequences and we
  // assume that a garbage collection will allow the subsequent
  // allocation attempts to go through.
  allocation_timeout_ = Max(6, FLAG_gc_interval);
#endif

  { GCTracer tracer;
    GarbageCollectionPrologue();
    // The GC count was incremented in the prologue.  Tell the tracer about
    // it.
    tracer.set_gc_count(gc_count_);

    GarbageCollector collector = SelectGarbageCollector(space);
    // Tell the tracer which collector we've selected.
    tracer.set_collector(collector);

    StatsRate* rate = (collector == SCAVENGER)
        ? &Counters::gc_scavenger
        : &Counters::gc_compactor;
    rate->Start();
    PerformGarbageCollection(space, collector, &tracer);
    rate->Stop();

    GarbageCollectionEpilogue();
  }


#ifdef ENABLE_LOGGING_AND_PROFILING
  if (FLAG_log_gc) HeapProfiler::WriteSample();
#endif

  switch (space) {
    case NEW_SPACE:
      return new_space_->Available() >= requested_size;
    case OLD_POINTER_SPACE:
      return old_pointer_space_->Available() >= requested_size;
    case OLD_DATA_SPACE:
      return old_data_space_->Available() >= requested_size;
    case CODE_SPACE:
      return code_space_->Available() >= requested_size;
    case MAP_SPACE:
      return map_space_->Available() >= requested_size;
    case LO_SPACE:
      return lo_space_->Available() >= requested_size;
  }
  return false;
}


void Heap::PerformScavenge() {
  GCTracer tracer;
  PerformGarbageCollection(NEW_SPACE, SCAVENGER, &tracer);
}


void Heap::PerformGarbageCollection(AllocationSpace space,
                                    GarbageCollector collector,
                                    GCTracer* tracer) {
  if (collector == MARK_COMPACTOR && global_gc_prologue_callback_) {
    ASSERT(!allocation_allowed_);
    global_gc_prologue_callback_();
  }

  if (collector == MARK_COMPACTOR) {
    MarkCompact(tracer);

    int promoted_space_size = PromotedSpaceSize();
    promoted_space_limit_ =
        promoted_space_size + Max(2 * MB, (promoted_space_size/100) * 35);
    old_gen_exhausted_ = false;

    // If we have used the mark-compact collector to collect the new
    // space, and it has not compacted the new space, we force a
    // separate scavenge collection.  This is a hack.  It covers the
    // case where (1) a new space collection was requested, (2) the
    // collector selection policy selected the mark-compact collector,
    // and (3) the mark-compact collector policy selected not to
    // compact the new space.  In that case, there is no more (usable)
    // free space in the new space after the collection compared to
    // before.
    if (space == NEW_SPACE && !MarkCompactCollector::HasCompacted()) {
      Scavenge();
    }
  } else {
    Scavenge();
  }
  Counters::objs_since_last_young.Set(0);

  // Process weak handles post gc.
  GlobalHandles::PostGarbageCollectionProcessing();

  if (collector == MARK_COMPACTOR) {
    // Register the amount of external allocated memory.
    amount_of_external_allocated_memory_at_last_global_gc_ =
        amount_of_external_allocated_memory_;
  }

  if (collector == MARK_COMPACTOR && global_gc_epilogue_callback_) {
    ASSERT(!allocation_allowed_);
    global_gc_epilogue_callback_();
  }
}