CSE2410 Fall 2014 Bounce

// Copyright 2012 the V8 project authors. All rights reserved.

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// modification, are permitted provided that the following conditions are

// met:

//

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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,

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#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