src/runtime-profiler.cc - platform/external/chromium_org/v8 - Git at Google

 // Copyright 2012 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 "runtime-profiler.h"

 #include "assembler.h"
 #include "bootstrapper.h"
 #include "code-stubs.h"
 #include "compilation-cache.h"
 #include "execution.h"
 #include "full-codegen.h"
 #include "global-handles.h"
 #include "isolate-inl.h"
 #include "mark-compact.h"
 #include "platform.h"
 #include "scopeinfo.h"

 namespace v8 {
 namespace internal {


 // Optimization sampler constants.
 static const int kSamplerFrameCount = 2;

 // Constants for statistical profiler.
 static const int kSamplerFrameWeight[kSamplerFrameCount] = { 2, 1 };

 static const int kSamplerTicksBetweenThresholdAdjustment = 32;

 static const int kSamplerThresholdInit = 3;
 static const int kSamplerThresholdMin = 1;
 static const int kSamplerThresholdDelta = 1;

 static const int kSamplerThresholdSizeFactorInit = 3;

 static const int kSizeLimit = 1500;

 // Constants for counter based profiler.

 // Number of times a function has to be seen on the stack before it is
 // optimized.
 static const int kProfilerTicksBeforeOptimization = 2;
 // If the function optimization was disabled due to high deoptimization count,
 // but the function is hot and has been seen on the stack this number of times,
 // then we try to reenable optimization for this function.
 static const int kProfilerTicksBeforeReenablingOptimization = 250;
 // If a function does not have enough type info (according to
 // FLAG_type_info_threshold), but has seen a huge number of ticks,
 // optimize it as it is.
 static const int kTicksWhenNotEnoughTypeInfo = 100;
 // We only have one byte to store the number of ticks.
 STATIC_ASSERT(kProfilerTicksBeforeOptimization < 256);
 STATIC_ASSERT(kProfilerTicksBeforeReenablingOptimization < 256);
 STATIC_ASSERT(kTicksWhenNotEnoughTypeInfo < 256);

 // Maximum size in bytes of generate code for a function to allow OSR.
 static const int kOSRCodeSizeAllowanceBase =
     100 * FullCodeGenerator::kCodeSizeMultiplier;

 static const int kOSRCodeSizeAllowancePerTick =
     3 * FullCodeGenerator::kCodeSizeMultiplier;

 // Maximum size in bytes of generated code for a function to be optimized
 // the very first time it is seen on the stack.
 static const int kMaxSizeEarlyOpt =
     5 * FullCodeGenerator::kCodeSizeMultiplier;


 RuntimeProfiler::RuntimeProfiler(Isolate* isolate)
     : isolate_(isolate),
       sampler_threshold_(kSamplerThresholdInit),
       sampler_threshold_size_factor_(kSamplerThresholdSizeFactorInit),
       sampler_ticks_until_threshold_adjustment_(
           kSamplerTicksBetweenThresholdAdjustment),
       sampler_window_position_(0),
       any_ic_changed_(false),
       code_generated_(false) {
   ClearSampleBuffer();
 }


 static void GetICCounts(Code* shared_code,
                         int* ic_with_type_info_count,
                         int* ic_total_count,
                         int* percentage) {
   *ic_total_count = 0;
   *ic_with_type_info_count = 0;
   Object* raw_info = shared_code->type_feedback_info();
   if (raw_info->IsTypeFeedbackInfo()) {
     TypeFeedbackInfo* info = TypeFeedbackInfo::cast(raw_info);
     *ic_with_type_info_count = info->ic_with_type_info_count();
     *ic_total_count = info->ic_total_count();
   }
   *percentage = *ic_total_count > 0
       ? 100 * *ic_with_type_info_count / *ic_total_count
       : 100;
 }


 void RuntimeProfiler::Optimize(JSFunction* function, const char* reason) {
   ASSERT(function->IsOptimizable());

   if (FLAG_trace_opt && function->PassesFilter(FLAG_hydrogen_filter)) {
     PrintF("[marking ");
     function->ShortPrint();
     PrintF(" for recompilation, reason: %s", reason);
     if (FLAG_type_info_threshold > 0) {
       int typeinfo, total, percentage;
       GetICCounts(function->shared()->code(), &typeinfo, &total, &percentage);
       PrintF(", ICs with typeinfo: %d/%d (%d%%)", typeinfo, total, percentage);
     }
     PrintF("]\n");
   }


   if (FLAG_concurrent_recompilation && !isolate_->bootstrapper()->IsActive()) {
     if (FLAG_concurrent_osr &&
         isolate_->optimizing_compiler_thread()->IsQueuedForOSR(function)) {
       // Do not attempt regular recompilation if we already queued this for OSR.
       // TODO(yangguo): This is necessary so that we don't install optimized
       // code on a function that is already optimized, since OSR and regular
       // recompilation race.  This goes away as soon as OSR becomes one-shot.
       return;
     }
     ASSERT(!function->IsInRecompileQueue());
     function->MarkForConcurrentRecompilation();
   } else {
     // The next call to the function will trigger optimization.
     function->MarkForLazyRecompilation();
   }
 }


 void RuntimeProfiler::AttemptOnStackReplacement(JSFunction* function) {
   // See AlwaysFullCompiler (in compiler.cc) comment on why we need
   // Debug::has_break_points().
   if (!FLAG_use_osr ||
       isolate_->DebuggerHasBreakPoints() ||
       function->IsBuiltin()) {
     return;
   }

   SharedFunctionInfo* shared = function->shared();
   // If the code is not optimizable, don't try OSR.
   if (!shared->code()->optimizable()) return;

   // We are not prepared to do OSR for a function that already has an
   // allocated arguments object.  The optimized code would bypass it for
   // arguments accesses, which is unsound.  Don't try OSR.
   if (shared->uses_arguments()) return;

   // We're using on-stack replacement: patch the unoptimized code so that
   // any back edge in any unoptimized frame will trigger on-stack
   // replacement for that frame.
   if (FLAG_trace_osr) {
     PrintF("[OSR - patching back edges in ");
     function->PrintName();
     PrintF("]\n");
   }

   BackEdgeTable::Patch(isolate_, shared->code());
 }


 void RuntimeProfiler::ClearSampleBuffer() {
   memset(sampler_window_, 0, sizeof(sampler_window_));
   memset(sampler_window_weight_, 0, sizeof(sampler_window_weight_));
 }


 int RuntimeProfiler::LookupSample(JSFunction* function) {
   int weight = 0;
   for (int i = 0; i < kSamplerWindowSize; i++) {
     Object* sample = sampler_window_[i];
     if (sample != NULL) {
       bool fits = FLAG_lookup_sample_by_shared
           ? (function->shared() == JSFunction::cast(sample)->shared())
           : (function == JSFunction::cast(sample));
       if (fits) {
         weight += sampler_window_weight_[i];
       }
     }
   }
   return weight;
 }


 void RuntimeProfiler::AddSample(JSFunction* function, int weight) {
   ASSERT(IsPowerOf2(kSamplerWindowSize));
   sampler_window_[sampler_window_position_] = function;
   sampler_window_weight_[sampler_window_position_] = weight;
   sampler_window_position_ = (sampler_window_position_ + 1) &
       (kSamplerWindowSize - 1);
 }


 void RuntimeProfiler::OptimizeNow() {
   HandleScope scope(isolate_);

   if (isolate_->DebuggerHasBreakPoints()) return;

   DisallowHeapAllocation no_gc;

   // Run through the JavaScript frames and collect them. If we already
   // have a sample of the function, we mark it for optimizations
   // (eagerly or lazily).
   JSFunction* samples[kSamplerFrameCount];
   int sample_count = 0;
   int frame_count = 0;
   int frame_count_limit = FLAG_watch_ic_patching ? FLAG_frame_count
                                                  : kSamplerFrameCount;
   for (JavaScriptFrameIterator it(isolate_);
        frame_count++ < frame_count_limit && !it.done();
        it.Advance()) {
     JavaScriptFrame* frame = it.frame();
     JSFunction* function = frame->function();

     if (!FLAG_watch_ic_patching) {
       // Adjust threshold each time we have processed
       // a certain number of ticks.
       if (sampler_ticks_until_threshold_adjustment_ > 0) {
         sampler_ticks_until_threshold_adjustment_--;
         if (sampler_ticks_until_threshold_adjustment_ <= 0) {
           // If the threshold is not already at the minimum
           // modify and reset the ticks until next adjustment.
           if (sampler_threshold_ > kSamplerThresholdMin) {
             sampler_threshold_ -= kSamplerThresholdDelta;
             sampler_ticks_until_threshold_adjustment_ =
                 kSamplerTicksBetweenThresholdAdjustment;
           }
         }
       }
     }

     SharedFunctionInfo* shared = function->shared();
     Code* shared_code = shared->code();

     if (shared_code->kind() != Code::FUNCTION) continue;
     if (function->IsInRecompileQueue()) continue;

     if (FLAG_always_osr &&
         shared_code->allow_osr_at_loop_nesting_level() == 0) {
       // Testing mode: always try an OSR compile for every function.
       for (int i = 0; i < Code::kMaxLoopNestingMarker; i++) {
         // TODO(titzer): fix AttemptOnStackReplacement to avoid this dumb loop.
         shared_code->set_allow_osr_at_loop_nesting_level(i);
         AttemptOnStackReplacement(function);
       }
       // Fall through and do a normal optimized compile as well.
     } else if (!frame->is_optimized() &&
         (function->IsMarkedForLazyRecompilation() ||
          function->IsMarkedForConcurrentRecompilation() ||
          function->IsOptimized())) {
       // Attempt OSR if we are still running unoptimized code even though the
       // the function has long been marked or even already been optimized.
       int ticks = shared_code->profiler_ticks();
       int allowance = kOSRCodeSizeAllowanceBase +
                       ticks * kOSRCodeSizeAllowancePerTick;
       if (shared_code->CodeSize() > allowance) {
         if (ticks < 255) shared_code->set_profiler_ticks(ticks + 1);
       } else {
         int nesting = shared_code->allow_osr_at_loop_nesting_level();
         if (nesting < Code::kMaxLoopNestingMarker) {
           int new_nesting = nesting + 1;
           shared_code->set_allow_osr_at_loop_nesting_level(new_nesting);
           AttemptOnStackReplacement(function);
         }
       }
       continue;
     }

     // Only record top-level code on top of the execution stack and
     // avoid optimizing excessively large scripts since top-level code
     // will be executed only once.
     const int kMaxToplevelSourceSize = 10 * 1024;
     if (shared->is_toplevel() &&
         (frame_count > 1 || shared->SourceSize() > kMaxToplevelSourceSize)) {
       continue;
     }

     // Do not record non-optimizable functions.
     if (shared->optimization_disabled()) {
       if (shared->deopt_count() >= FLAG_max_opt_count) {
         // If optimization was disabled due to many deoptimizations,
         // then check if the function is hot and try to reenable optimization.
         int ticks = shared_code->profiler_ticks();
         if (ticks >= kProfilerTicksBeforeReenablingOptimization) {
           shared_code->set_profiler_ticks(0);
           shared->TryReenableOptimization();
         } else {
           shared_code->set_profiler_ticks(ticks + 1);
         }
       }
       continue;
     }
     if (!function->IsOptimizable()) continue;

     if (FLAG_watch_ic_patching) {
       int ticks = shared_code->profiler_ticks();

       if (ticks >= kProfilerTicksBeforeOptimization) {
         int typeinfo, total, percentage;
         GetICCounts(shared_code, &typeinfo, &total, &percentage);
         if (percentage >= FLAG_type_info_threshold) {
           // If this particular function hasn't had any ICs patched for enough
           // ticks, optimize it now.
           Optimize(function, "hot and stable");
         } else if (ticks >= kTicksWhenNotEnoughTypeInfo) {
           Optimize(function, "not much type info but very hot");
         } else {
           shared_code->set_profiler_ticks(ticks + 1);
           if (FLAG_trace_opt_verbose) {
             PrintF("[not yet optimizing ");
             function->PrintName();
             PrintF(", not enough type info: %d/%d (%d%%)]\n",
                    typeinfo, total, percentage);
           }
         }
       } else if (!any_ic_changed_ &&
                  shared_code->instruction_size() < kMaxSizeEarlyOpt) {
         // If no IC was patched since the last tick and this function is very
         // small, optimistically optimize it now.
         Optimize(function, "small function");
       } else {
         shared_code->set_profiler_ticks(ticks + 1);
       }
     } else {  // !FLAG_watch_ic_patching
       samples[sample_count++] = function;

       int function_size = function->shared()->SourceSize();
       int threshold_size_factor = (function_size > kSizeLimit)
           ? sampler_threshold_size_factor_
           : 1;

       int threshold = sampler_threshold_ * threshold_size_factor;

       if (LookupSample(function) >= threshold) {
         Optimize(function, "sampler window lookup");
       }
     }
   }
   if (FLAG_watch_ic_patching) {
     any_ic_changed_ = false;
   } else {  // !FLAG_watch_ic_patching
     // Add the collected functions as samples. It's important not to do
     // this as part of collecting them because this will interfere with
     // the sample lookup in case of recursive functions.
     for (int i = 0; i < sample_count; i++) {
       AddSample(samples[i], kSamplerFrameWeight[i]);
     }
   }
 }


 void RuntimeProfiler::SetUp() {
   if (!FLAG_watch_ic_patching) {
     ClearSampleBuffer();
   }
 }


 void RuntimeProfiler::Reset() {
   if (!FLAG_watch_ic_patching) {
     sampler_threshold_ = kSamplerThresholdInit;
     sampler_threshold_size_factor_ = kSamplerThresholdSizeFactorInit;
     sampler_ticks_until_threshold_adjustment_ =
         kSamplerTicksBetweenThresholdAdjustment;
   }
 }


 void RuntimeProfiler::TearDown() {
   // Nothing to do.
 }


 // Update the pointers in the sampler window after a GC.
 void RuntimeProfiler::UpdateSamplesAfterScavenge() {
   for (int i = 0; i < kSamplerWindowSize; i++) {
     Object* function = sampler_window_[i];
     if (function != NULL && isolate_->heap()->InNewSpace(function)) {
       MapWord map_word = HeapObject::cast(function)->map_word();
       if (map_word.IsForwardingAddress()) {
         sampler_window_[i] = map_word.ToForwardingAddress();
       } else {
         sampler_window_[i] = NULL;
       }
     }
   }
 }


 void RuntimeProfiler::RemoveDeadSamples() {
   for (int i = 0; i < kSamplerWindowSize; i++) {
     Object* function = sampler_window_[i];
     if (function != NULL &&
         !Marking::MarkBitFrom(HeapObject::cast(function)).Get()) {
       sampler_window_[i] = NULL;
     }
   }
 }


 void RuntimeProfiler::UpdateSamplesAfterCompact(ObjectVisitor* visitor) {
   for (int i = 0; i < kSamplerWindowSize; i++) {
     visitor->VisitPointer(&sampler_window_[i]);
   }
 }


 } }  // namespace v8::internal
	// Copyright 2012 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 "runtime-profiler.h"

	#include "assembler.h"
	#include "bootstrapper.h"
	#include "code-stubs.h"
	#include "compilation-cache.h"
	#include "execution.h"
	#include "full-codegen.h"
	#include "global-handles.h"
	#include "isolate-inl.h"
	#include "mark-compact.h"
	#include "platform.h"
	#include "scopeinfo.h"

	namespace v8 {
	namespace internal {


	// Optimization sampler constants.
	static const int kSamplerFrameCount = 2;

	// Constants for statistical profiler.
	static const int kSamplerFrameWeight[kSamplerFrameCount] = { 2, 1 };

	static const int kSamplerTicksBetweenThresholdAdjustment = 32;

	static const int kSamplerThresholdInit = 3;
	static const int kSamplerThresholdMin = 1;
	static const int kSamplerThresholdDelta = 1;

	static const int kSamplerThresholdSizeFactorInit = 3;

	static const int kSizeLimit = 1500;

	// Constants for counter based profiler.

	// Number of times a function has to be seen on the stack before it is
	// optimized.
	static const int kProfilerTicksBeforeOptimization = 2;
	// If the function optimization was disabled due to high deoptimization count,
	// but the function is hot and has been seen on the stack this number of times,
	// then we try to reenable optimization for this function.
	static const int kProfilerTicksBeforeReenablingOptimization = 250;
	// If a function does not have enough type info (according to
	// FLAG_type_info_threshold), but has seen a huge number of ticks,
	// optimize it as it is.
	static const int kTicksWhenNotEnoughTypeInfo = 100;
	// We only have one byte to store the number of ticks.
	STATIC_ASSERT(kProfilerTicksBeforeOptimization < 256);
	STATIC_ASSERT(kProfilerTicksBeforeReenablingOptimization < 256);
	STATIC_ASSERT(kTicksWhenNotEnoughTypeInfo < 256);

	// Maximum size in bytes of generate code for a function to allow OSR.
	static const int kOSRCodeSizeAllowanceBase =
	100 * FullCodeGenerator::kCodeSizeMultiplier;

	static const int kOSRCodeSizeAllowancePerTick =
	3 * FullCodeGenerator::kCodeSizeMultiplier;

	// Maximum size in bytes of generated code for a function to be optimized
	// the very first time it is seen on the stack.
	static const int kMaxSizeEarlyOpt =
	5 * FullCodeGenerator::kCodeSizeMultiplier;


	RuntimeProfiler::RuntimeProfiler(Isolate* isolate)
	: isolate_(isolate),
	sampler_threshold_(kSamplerThresholdInit),
	sampler_threshold_size_factor_(kSamplerThresholdSizeFactorInit),
	sampler_ticks_until_threshold_adjustment_(
	kSamplerTicksBetweenThresholdAdjustment),
	sampler_window_position_(0),
	any_ic_changed_(false),
	code_generated_(false) {
	ClearSampleBuffer();
	}


	static void GetICCounts(Code* shared_code,
	int* ic_with_type_info_count,
	int* ic_total_count,
	int* percentage) {
	*ic_total_count = 0;
	*ic_with_type_info_count = 0;
	Object* raw_info = shared_code->type_feedback_info();
	if (raw_info->IsTypeFeedbackInfo()) {
	TypeFeedbackInfo* info = TypeFeedbackInfo::cast(raw_info);
	*ic_with_type_info_count = info->ic_with_type_info_count();
	*ic_total_count = info->ic_total_count();
	}
	percentage = ic_total_count > 0
	? 100 * ic_with_type_info_count / ic_total_count
	: 100;
	}


	void RuntimeProfiler::Optimize(JSFunction* function, const char* reason) {
	ASSERT(function->IsOptimizable());

	if (FLAG_trace_opt && function->PassesFilter(FLAG_hydrogen_filter)) {
	PrintF("[marking ");
	function->ShortPrint();
	PrintF(" for recompilation, reason: %s", reason);
	if (FLAG_type_info_threshold > 0) {
	int typeinfo, total, percentage;
	GetICCounts(function->shared()->code(), &typeinfo, &total, &percentage);
	PrintF(", ICs with typeinfo: %d/%d (%d%%)", typeinfo, total, percentage);
	}
	PrintF("]\n");
	}


	if (FLAG_concurrent_recompilation && !isolate_->bootstrapper()->IsActive()) {
	if (FLAG_concurrent_osr &&
	isolate_->optimizing_compiler_thread()->IsQueuedForOSR(function)) {
	// Do not attempt regular recompilation if we already queued this for OSR.
	// TODO(yangguo): This is necessary so that we don't install optimized
	// code on a function that is already optimized, since OSR and regular
	// recompilation race. This goes away as soon as OSR becomes one-shot.
	return;
	}
	ASSERT(!function->IsInRecompileQueue());
	function->MarkForConcurrentRecompilation();
	} else {
	// The next call to the function will trigger optimization.
	function->MarkForLazyRecompilation();
	}
	}


	void RuntimeProfiler::AttemptOnStackReplacement(JSFunction* function) {
	// See AlwaysFullCompiler (in compiler.cc) comment on why we need
	// Debug::has_break_points().
	if (!FLAG_use_osr \|\|
	isolate_->DebuggerHasBreakPoints() \|\|
	function->IsBuiltin()) {
	return;
	}

	SharedFunctionInfo* shared = function->shared();
	// If the code is not optimizable, don't try OSR.
	if (!shared->code()->optimizable()) return;

	// We are not prepared to do OSR for a function that already has an
	// allocated arguments object. The optimized code would bypass it for
	// arguments accesses, which is unsound. Don't try OSR.
	if (shared->uses_arguments()) return;

	// We're using on-stack replacement: patch the unoptimized code so that
	// any back edge in any unoptimized frame will trigger on-stack
	// replacement for that frame.
	if (FLAG_trace_osr) {
	PrintF("[OSR - patching back edges in ");
	function->PrintName();
	PrintF("]\n");
	}

	BackEdgeTable::Patch(isolate_, shared->code());
	}


	void RuntimeProfiler::ClearSampleBuffer() {
	memset(sampler_window_, 0, sizeof(sampler_window_));
	memset(sampler_window_weight_, 0, sizeof(sampler_window_weight_));
	}


	int RuntimeProfiler::LookupSample(JSFunction* function) {
	int weight = 0;
	for (int i = 0; i < kSamplerWindowSize; i++) {
	Object* sample = sampler_window_[i];
	if (sample != NULL) {
	bool fits = FLAG_lookup_sample_by_shared
	? (function->shared() == JSFunction::cast(sample)->shared())
	: (function == JSFunction::cast(sample));
	if (fits) {
	weight += sampler_window_weight_[i];
	}
	}
	}
	return weight;
	}


	void RuntimeProfiler::AddSample(JSFunction* function, int weight) {
	ASSERT(IsPowerOf2(kSamplerWindowSize));
	sampler_window_[sampler_window_position_] = function;
	sampler_window_weight_[sampler_window_position_] = weight;
	sampler_window_position_ = (sampler_window_position_ + 1) &
	(kSamplerWindowSize - 1);
	}


	void RuntimeProfiler::OptimizeNow() {
	HandleScope scope(isolate_);

	if (isolate_->DebuggerHasBreakPoints()) return;

	DisallowHeapAllocation no_gc;

	// Run through the JavaScript frames and collect them. If we already
	// have a sample of the function, we mark it for optimizations
	// (eagerly or lazily).
	JSFunction* samples[kSamplerFrameCount];
	int sample_count = 0;
	int frame_count = 0;
	int frame_count_limit = FLAG_watch_ic_patching ? FLAG_frame_count
	: kSamplerFrameCount;
	for (JavaScriptFrameIterator it(isolate_);
	frame_count++ < frame_count_limit && !it.done();
	it.Advance()) {
	JavaScriptFrame* frame = it.frame();
	JSFunction* function = frame->function();

	if (!FLAG_watch_ic_patching) {
	// Adjust threshold each time we have processed
	// a certain number of ticks.
	if (sampler_ticks_until_threshold_adjustment_ > 0) {
	sampler_ticks_until_threshold_adjustment_--;
	if (sampler_ticks_until_threshold_adjustment_ <= 0) {
	// If the threshold is not already at the minimum
	// modify and reset the ticks until next adjustment.
	if (sampler_threshold_ > kSamplerThresholdMin) {
	sampler_threshold_ -= kSamplerThresholdDelta;
	sampler_ticks_until_threshold_adjustment_ =
	kSamplerTicksBetweenThresholdAdjustment;
	}
	}
	}
	}

	SharedFunctionInfo* shared = function->shared();
	Code* shared_code = shared->code();

	if (shared_code->kind() != Code::FUNCTION) continue;
	if (function->IsInRecompileQueue()) continue;

	if (FLAG_always_osr &&
	shared_code->allow_osr_at_loop_nesting_level() == 0) {
	// Testing mode: always try an OSR compile for every function.
	for (int i = 0; i < Code::kMaxLoopNestingMarker; i++) {
	// TODO(titzer): fix AttemptOnStackReplacement to avoid this dumb loop.
	shared_code->set_allow_osr_at_loop_nesting_level(i);
	AttemptOnStackReplacement(function);
	}
	// Fall through and do a normal optimized compile as well.
	} else if (!frame->is_optimized() &&
	(function->IsMarkedForLazyRecompilation() \|\|
	function->IsMarkedForConcurrentRecompilation() \|\|
	function->IsOptimized())) {
	// Attempt OSR if we are still running unoptimized code even though the
	// the function has long been marked or even already been optimized.
	int ticks = shared_code->profiler_ticks();
	int allowance = kOSRCodeSizeAllowanceBase +
	ticks * kOSRCodeSizeAllowancePerTick;
	if (shared_code->CodeSize() > allowance) {
	if (ticks < 255) shared_code->set_profiler_ticks(ticks + 1);
	} else {
	int nesting = shared_code->allow_osr_at_loop_nesting_level();
	if (nesting < Code::kMaxLoopNestingMarker) {
	int new_nesting = nesting + 1;
	shared_code->set_allow_osr_at_loop_nesting_level(new_nesting);
	AttemptOnStackReplacement(function);
	}
	}
	continue;
	}

	// Only record top-level code on top of the execution stack and
	// avoid optimizing excessively large scripts since top-level code
	// will be executed only once.
	const int kMaxToplevelSourceSize = 10 * 1024;
	if (shared->is_toplevel() &&
	(frame_count > 1 \|\| shared->SourceSize() > kMaxToplevelSourceSize)) {
	continue;
	}

	// Do not record non-optimizable functions.
	if (shared->optimization_disabled()) {
	if (shared->deopt_count() >= FLAG_max_opt_count) {
	// If optimization was disabled due to many deoptimizations,
	// then check if the function is hot and try to reenable optimization.
	int ticks = shared_code->profiler_ticks();
	if (ticks >= kProfilerTicksBeforeReenablingOptimization) {
	shared_code->set_profiler_ticks(0);
	shared->TryReenableOptimization();
	} else {
	shared_code->set_profiler_ticks(ticks + 1);
	}
	}
	continue;
	}
	if (!function->IsOptimizable()) continue;

	if (FLAG_watch_ic_patching) {
	int ticks = shared_code->profiler_ticks();

	if (ticks >= kProfilerTicksBeforeOptimization) {
	int typeinfo, total, percentage;
	GetICCounts(shared_code, &typeinfo, &total, &percentage);
	if (percentage >= FLAG_type_info_threshold) {
	// If this particular function hasn't had any ICs patched for enough
	// ticks, optimize it now.
	Optimize(function, "hot and stable");
	} else if (ticks >= kTicksWhenNotEnoughTypeInfo) {
	Optimize(function, "not much type info but very hot");
	} else {
	shared_code->set_profiler_ticks(ticks + 1);
	if (FLAG_trace_opt_verbose) {
	PrintF("[not yet optimizing ");
	function->PrintName();
	PrintF(", not enough type info: %d/%d (%d%%)]\n",
	typeinfo, total, percentage);
	}
	}
	} else if (!any_ic_changed_ &&
	shared_code->instruction_size() < kMaxSizeEarlyOpt) {
	// If no IC was patched since the last tick and this function is very
	// small, optimistically optimize it now.
	Optimize(function, "small function");
	} else {
	shared_code->set_profiler_ticks(ticks + 1);
	}
	} else { // !FLAG_watch_ic_patching
	samples[sample_count++] = function;

	int function_size = function->shared()->SourceSize();
	int threshold_size_factor = (function_size > kSizeLimit)
	? sampler_threshold_size_factor_
	: 1;

	int threshold = sampler_threshold_ * threshold_size_factor;

	if (LookupSample(function) >= threshold) {
	Optimize(function, "sampler window lookup");
	}
	}
	}
	if (FLAG_watch_ic_patching) {
	any_ic_changed_ = false;
	} else { // !FLAG_watch_ic_patching
	// Add the collected functions as samples. It's important not to do
	// this as part of collecting them because this will interfere with
	// the sample lookup in case of recursive functions.
	for (int i = 0; i < sample_count; i++) {
	AddSample(samples[i], kSamplerFrameWeight[i]);
	}
	}
	}


	void RuntimeProfiler::SetUp() {
	if (!FLAG_watch_ic_patching) {
	ClearSampleBuffer();
	}
	}


	void RuntimeProfiler::Reset() {
	if (!FLAG_watch_ic_patching) {
	sampler_threshold_ = kSamplerThresholdInit;
	sampler_threshold_size_factor_ = kSamplerThresholdSizeFactorInit;
	sampler_ticks_until_threshold_adjustment_ =
	kSamplerTicksBetweenThresholdAdjustment;
	}
	}


	void RuntimeProfiler::TearDown() {
	// Nothing to do.
	}


	// Update the pointers in the sampler window after a GC.
	void RuntimeProfiler::UpdateSamplesAfterScavenge() {
	for (int i = 0; i < kSamplerWindowSize; i++) {
	Object* function = sampler_window_[i];
	if (function != NULL && isolate_->heap()->InNewSpace(function)) {
	MapWord map_word = HeapObject::cast(function)->map_word();
	if (map_word.IsForwardingAddress()) {
	sampler_window_[i] = map_word.ToForwardingAddress();
	} else {
	sampler_window_[i] = NULL;
	}
	}
	}
	}


	void RuntimeProfiler::RemoveDeadSamples() {
	for (int i = 0; i < kSamplerWindowSize; i++) {
	Object* function = sampler_window_[i];
	if (function != NULL &&
	!Marking::MarkBitFrom(HeapObject::cast(function)).Get()) {
	sampler_window_[i] = NULL;
	}
	}
	}


	void RuntimeProfiler::UpdateSamplesAfterCompact(ObjectVisitor* visitor) {
	for (int i = 0; i < kSamplerWindowSize; i++) {
	visitor->VisitPointer(&sampler_window_[i]);
	}
	}


	} } // namespace v8::internal