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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 js_SliceBudget_h
#define js_SliceBudget_h
#include "mozilla/Assertions.h"
#include "mozilla/TimeStamp.h"
#include "mozilla/Variant.h"
#include <stdint.h>
#include "jstypes.h"
namespace js {
struct JS_PUBLIC_API TimeBudget {
const int64_t budget;
mozilla::TimeStamp deadline; // Calculated when SliceBudget is constructed.
explicit TimeBudget(int64_t milliseconds) : budget(milliseconds) {}
explicit TimeBudget(mozilla::TimeDuration duration)
: TimeBudget(duration.ToMilliseconds()) {}
};
struct JS_PUBLIC_API WorkBudget {
const int64_t budget;
explicit WorkBudget(int64_t work) : budget(work) {}
};
struct UnlimitedBudget {};
/*
* This class describes a limit to the amount of work to be performed in a GC
* slice, so that we can return to the mutator without pausing for too long. The
* budget may be based on a deadline time or an amount of work to be performed,
* or may be unlimited.
*
* To reduce the number of gettimeofday calls, we only check the time every 1000
* operations.
*/
class JS_PUBLIC_API SliceBudget {
static const intptr_t UnlimitedCounter = INTPTR_MAX;
static const intptr_t DefaultStepsPerTimeCheck = 1000;
mozilla::Variant<TimeBudget, WorkBudget, UnlimitedBudget> budget;
int64_t stepsPerTimeCheck = DefaultStepsPerTimeCheck;
int64_t counter;
SliceBudget() : budget(UnlimitedBudget()), counter(UnlimitedCounter) {}
bool checkOverBudget();
public:
// Use to create an unlimited budget.
static SliceBudget unlimited() { return SliceBudget(); }
// Instantiate as SliceBudget(TimeBudget(n)).
explicit SliceBudget(TimeBudget time,
int64_t stepsPerTimeCheck = DefaultStepsPerTimeCheck);
// Instantiate as SliceBudget(WorkBudget(n)).
explicit SliceBudget(WorkBudget work);
explicit SliceBudget(mozilla::TimeDuration time)
: SliceBudget(TimeBudget(time.ToMilliseconds())) {}
// Register having performed the given number of steps (counted against a
// work budget, or progress towards the next time or callback check).
void step(uint64_t steps = 1) {
MOZ_ASSERT(steps > 0);
counter -= steps;
}
// Do enough steps to force an "expensive" (time and/or callback) check on
// the next call to isOverBudget. Useful when switching between major phases
// of an operation like a cycle collection.
void stepAndForceCheck() {
if (!isUnlimited()) {
counter = 0;
}
}
bool isOverBudget() { return counter <= 0 && checkOverBudget(); }
bool isWorkBudget() const { return budget.is<WorkBudget>(); }
bool isTimeBudget() const { return budget.is<TimeBudget>(); }
bool isUnlimited() const { return budget.is<UnlimitedBudget>(); }
int64_t timeBudget() const { return budget.as<TimeBudget>().budget; }
int64_t workBudget() const { return budget.as<WorkBudget>().budget; }
mozilla::TimeStamp deadline() const {
return budget.as<TimeBudget>().deadline;
}
int describe(char* buffer, size_t maxlen) const;
};
} // namespace js
#endif /* js_SliceBudget_h */