// Copyright 2016 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef V8_LIBSAMPLER_SAMPLER_H_
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#define V8_LIBSAMPLER_SAMPLER_H_
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#include "include/v8.h"
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#include "src/base/atomicops.h"
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#include "src/base/macros.h"
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namespace v8 {
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namespace sampler {
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// ----------------------------------------------------------------------------
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// Sampler
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//
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// A sampler periodically samples the state of the VM and optionally
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// (if used for profiling) the program counter and stack pointer for
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// the thread that created it.
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class Sampler {
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public:
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static const int kMaxFramesCountLog2 = 8;
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static const unsigned kMaxFramesCount = (1u << kMaxFramesCountLog2) - 1;
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// Initializes the Sampler support. Called once at VM startup.
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static void SetUp();
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static void TearDown();
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// Initialize sampler.
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explicit Sampler(Isolate* isolate);
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virtual ~Sampler();
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Isolate* isolate() const { return isolate_; }
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// Performs stack sampling.
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// Clients should override this method in order to do something on samples,
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// for example buffer samples in a queue.
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virtual void SampleStack(const v8::RegisterState& regs) = 0;
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// Start and stop sampler.
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void Start();
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void Stop();
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// Whether the sampling thread should use this Sampler for CPU profiling?
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bool IsProfiling() const {
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return base::Relaxed_Load(&profiling_) > 0 &&
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!base::Relaxed_Load(&has_processing_thread_);
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}
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void IncreaseProfilingDepth();
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void DecreaseProfilingDepth();
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// Whether the sampler is running (that is, consumes resources).
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bool IsActive() const { return base::Relaxed_Load(&active_) != 0; }
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// CpuProfiler collects samples by calling DoSample directly
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// without calling Start. To keep it working, we register the sampler
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// with the CpuProfiler.
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bool IsRegistered() const { return base::Relaxed_Load(®istered_) != 0; }
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void DoSample();
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void SetHasProcessingThread(bool value) {
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base::Relaxed_Store(&has_processing_thread_, value);
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}
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// Used in tests to make sure that stack sampling is performed.
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unsigned js_sample_count() const { return js_sample_count_; }
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unsigned external_sample_count() const { return external_sample_count_; }
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void StartCountingSamples() {
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js_sample_count_ = 0;
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external_sample_count_ = 0;
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is_counting_samples_ = true;
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}
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class PlatformData;
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PlatformData* platform_data() const { return data_; }
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protected:
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// Counts stack samples taken in various VM states.
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bool is_counting_samples_;
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unsigned js_sample_count_;
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unsigned external_sample_count_;
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private:
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void SetActive(bool value) { base::Relaxed_Store(&active_, value); }
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void SetRegistered(bool value) { base::Relaxed_Store(®istered_, value); }
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Isolate* isolate_;
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base::Atomic32 profiling_;
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base::Atomic32 has_processing_thread_;
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base::Atomic32 active_;
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base::Atomic32 registered_;
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PlatformData* data_; // Platform specific data.
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DISALLOW_IMPLICIT_CONSTRUCTORS(Sampler);
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};
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} // namespace sampler
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} // namespace v8
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#endif // V8_LIBSAMPLER_SAMPLER_H_
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