ladybird/Kernel/Time/APICTimer.h
Tom 5f51d85184 Kernel: Improve time keeping and dramatically reduce interrupt load
This implements a number of changes related to time:
* If a HPET is present, it is now used only as a system timer, unless
  the Local APIC timer is used (in which case the HPET timer will not
  trigger any interrupts at all).
* If a HPET is present, the current time can now be as accurate as the
  chip can be, independently from the system timer. We now query the
  HPET main counter for the current time in CPU #0's system timer
  interrupt, and use that as a base line. If a high precision time is
  queried, that base line is used in combination with quering the HPET
  timer directly, which should give a much more accurate time stamp at
  the expense of more overhead. For faster time stamps, the more coarse
  value based on the last interrupt will be returned. This also means
  that any missed interrupts should not cause the time to drift.
* The default system interrupt rate is reduced to about 250 per second.
* Fix calculation of Thread CPU usage by using the amount of ticks they
  used rather than the number of times a context switch happened.
* Implement CLOCK_REALTIME_COARSE and CLOCK_MONOTONIC_COARSE and use it
  for most cases where precise timestamps are not needed.
2020-12-21 18:26:12 +01:00

67 lines
2.7 KiB
C++

/*
* Copyright (c) 2020, the SerenityOS developers
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
*
* 2. 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.
*
* 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 HOLDER 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.
*/
#pragma once
#include <AK/NonnullRefPtr.h>
#include <AK/Types.h>
#include <Kernel/Interrupts/GenericInterruptHandler.h>
#include <Kernel/Time/HardwareTimer.h>
namespace Kernel {
class APICTimer final : public HardwareTimer<GenericInterruptHandler> {
public:
static APICTimer* initialize(u8, HardwareTimerBase&);
virtual HardwareTimerType timer_type() const override { return HardwareTimerType::LocalAPICTimer; }
virtual const char* model() const override { return "LocalAPIC"; }
virtual size_t ticks_per_second() const override;
virtual bool is_periodic() const override { return m_timer_mode == APIC::TimerMode::Periodic; }
virtual bool is_periodic_capable() const override { return true; }
virtual void set_periodic() override;
virtual void set_non_periodic() override;
virtual void disable() override { }
virtual void reset_to_default_ticks_per_second() override;
virtual bool try_to_set_frequency(size_t frequency) override;
virtual bool is_capable_of_frequency(size_t frequency) const override;
virtual size_t calculate_nearest_possible_frequency(size_t frequency) const override;
void enable_local_timer();
void disable_local_timer();
private:
explicit APICTimer(u8, Function<void(const RegisterState&)>);
bool calibrate(HardwareTimerBase&);
u32 m_timer_period { 0 };
APIC::TimerMode m_timer_mode { APIC::TimerMode::Periodic };
};
}