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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 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/. */
#ifndef mozilla_PerformanceCounter_h
#define mozilla_PerformanceCounter_h
#include "mozilla/Array.h"
#include "mozilla/Atomics.h"
#include "mozilla/TaskCategory.h"
#include "nsISupportsImpl.h"
#include "nsString.h"
namespace mozilla {
/*
* The DispatchCategory class is used to fake the inheritance
* of the TaskCategory enum so we can extend it to hold
* one more value corresponding to the category
* we use when a worker dispatches a call.
*
*/
class DispatchCategory final {
public:
explicit DispatchCategory(uint32_t aValue) : mValue(aValue) {
// Since DispatchCategory is adding one single value to the
// TaskCategory enum, we can check here that the value is
// the next index e.g. TaskCategory::Count
MOZ_ASSERT(aValue == (uint32_t)TaskCategory::Count);
}
constexpr explicit DispatchCategory(TaskCategory aValue)
: mValue((uint32_t)aValue) {}
uint32_t GetValue() const { return mValue; }
static const DispatchCategory Worker;
private:
uint32_t mValue;
};
typedef Array<Atomic<uint32_t>, (uint32_t)TaskCategory::Count + 1>
DispatchCounter;
// PerformanceCounter is a class that can be used to keep track of
// runnable execution times and dispatch counts.
//
// - runnable execution time: time spent in a runnable when called
// in nsThread::ProcessNextEvent (not counting recursive calls)
// - dispatch counts: number of times a tracked runnable is dispatched
// in nsThread. Useful to measure the activity of a tab or worker.
//
// The PerformanceCounter class is currently instantiated in DocGroup
// and WorkerPrivate in order to count how many scheduler dispatches
// are done through them, and how long the execution lasts.
//
// The execution time is calculated by the nsThread class (and its
// inherited WorkerThread class) in its ProcessNextEvent method.
//
// For each processed runnable, nsThread will reach out the
// PerformanceCounter attached to the runnable via its DocGroup
// or WorkerPrivate and call IncrementExecutionDuration()
//
// Notice that the execution duration counting takes into account
// recursivity. If an event triggers a recursive call to
// nsThread::ProcessNextEVent, the counter will discard the time
// spent in sub events.
class PerformanceCounter final {
public:
NS_INLINE_DECL_THREADSAFE_REFCOUNTING(PerformanceCounter)
explicit PerformanceCounter(const nsACString& aName);
/**
* This is called everytime a runnable is dispatched.
*
* aCategory can be used to distinguish counts per TaskCategory
*
* Note that an overflow will simply reset the counter.
*/
void IncrementDispatchCounter(DispatchCategory aCategory);
/**
* This is called via nsThread::ProcessNextEvent to measure runnable
* execution duration.
*
* Note that an overflow will simply reset the counter.
*/
void IncrementExecutionDuration(uint32_t aMicroseconds);
/**
* Returns a category/counter array of all dispatches.
*/
const DispatchCounter& GetDispatchCounter() const;
/**
* Returns the total execution duration.
*/
uint64_t GetExecutionDuration() const;
/**
* Returns the number of dispatches per TaskCategory.
*/
uint32_t GetDispatchCount(DispatchCategory aCategory) const;
/**
* Returns the total number of dispatches.
*/
uint64_t GetTotalDispatchCount() const;
/**
* Returns the unique id for the instance.
*
* Used to distinguish instances since the lifespan of
* a PerformanceCounter can be shorter than the
* host it's tracking. That leads to edge cases
* where a counter appears to have values that go
* backwards. Having this id let the consumers
* detect that they are dealing with a new counter
* when it happens.
*/
uint64_t GetID() const;
private:
~PerformanceCounter() = default;
Atomic<uint64_t> mExecutionDuration;
Atomic<uint64_t> mTotalDispatchCount;
DispatchCounter mDispatchCounter;
nsCString mName;
const uint64_t mID;
};
} // namespace mozilla
#endif // mozilla_PerformanceCounter_h
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