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Kernel: Improve time keeping and dramatically reduce interrupt load

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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.
This commit is contained in:
Tom 2020-12-03 22:12:50 -07:00 • committed by Andreas Kling
parent a3fdf5148b
commit 5f51d85184
32 changed files with 318 additions and 190 deletions
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8
Kernel/Time/HPET.h
View file

@ -45,7 +45,7 @@ public:
static bool check_for_exisiting_periodic_timers();
static HPET& the();
u64 frequency() const;
u64 frequency() const { return m_frequency; }
const NonnullRefPtrVector<HPETComparator>& comparators() const { return m_comparators; }
void disable(const HPETComparator&);
@ -59,6 +59,8 @@ public:
void enable_periodic_interrupt(const HPETComparator& comparator);
void disable_periodic_interrupt(const HPETComparator& comparator);
u64 update_time(u64& seconds_since_boot, u32& ticks_this_second, bool query_only);
Vector<unsigned> capable_interrupt_numbers(u8 comparator_number);
Vector<unsigned> capable_interrupt_numbers(const HPETComparator&);
@ -80,7 +82,9 @@ private:
PhysicalAddress m_physical_acpi_hpet_registers;
OwnPtr<Region> m_hpet_mmio_region;
u64 m_main_counter_clock_period { 0 };
u64 m_main_counter_last_read { 0 };
u64 m_main_counter_drift { 0 };
u16 m_vendor_id;
u16 m_minimum_tick;
u64 m_frequency;