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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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44
Kernel/Time/HPET.cpp
View file

@ -197,10 +197,14 @@ void HPET::update_periodic_comparator_value()
auto& regs = registers();
u64 previous_main_value = (u64)regs.main_counter_value.low | ((u64)regs.main_counter_value.high << 32);
m_main_counter_drift += previous_main_value - m_main_counter_last_read;
m_main_counter_last_read = 0;
regs.main_counter_value.low = 0;
regs.main_counter_value.high = 0;
for (auto& comparator : m_comparators) {
auto& timer = regs.timers[comparator.comparator_number()];
if (!comparator.is_enabled())
continue;
if (comparator.is_periodic()) {
// Note that this means we're restarting all periodic timers. There is no
// way to resume periodic timers properly because we reset the main counter
@ -242,6 +246,33 @@ void HPET::update_non_periodic_comparator_value(const HPETComparator& comparator
timer.comparator_value.low = (u32)new_counter_value;
}
u64 HPET::update_time(u64& seconds_since_boot, u32& ticks_this_second, bool query_only)
{
// Should only be called by the time keeper interrupt handler!
u64 current_value = read_register_safe64(registers().main_counter_value);
u64 delta_ticks = m_main_counter_drift;
if (current_value >= m_main_counter_last_read)
delta_ticks += current_value - m_main_counter_last_read;
else
delta_ticks += m_main_counter_last_read - current_value; // the counter wrapped around
u64 ticks_since_last_second = (u64)ticks_this_second + delta_ticks;
auto ticks_per_second = frequency();
if (ticks_since_last_second > ticks_per_second) {
seconds_since_boot += ticks_since_last_second / ticks_per_second;
ticks_this_second = ticks_since_last_second % ticks_per_second;
} else {
ticks_this_second = ticks_since_last_second;
}
if (!query_only) {
m_main_counter_drift = 0;
m_main_counter_last_read = current_value;
}
// Return the time passed (in ns) since last time update_time was called
return (delta_ticks * 1000000000ull) / ticks_per_second;
}
void HPET::enable_periodic_interrupt(const HPETComparator& comparator)
{
#ifdef HPET_DEBUG
@ -253,7 +284,8 @@ void HPET::enable_periodic_interrupt(const HPETComparator& comparator)
auto capabilities = timer.capabilities;
ASSERT(capabilities & (u32)HPETFlags::TimerConfiguration::PeriodicInterruptCapable);
timer.capabilities = capabilities | (u32)HPETFlags::TimerConfiguration::GeneratePeriodicInterrupt;
enable(comparator);
if (comparator.is_enabled())
enable(comparator);
}
void HPET::disable_periodic_interrupt(const HPETComparator& comparator)
{
@ -266,7 +298,8 @@ void HPET::disable_periodic_interrupt(const HPETComparator& comparator)
auto capabilities = timer.capabilities;
ASSERT(capabilities & (u32)HPETFlags::TimerConfiguration::PeriodicInterruptCapable);
timer.capabilities = capabilities & ~(u32)HPETFlags::TimerConfiguration::GeneratePeriodicInterrupt;
enable(comparator);
if (comparator.is_enabled())
enable(comparator);
}
void HPET::disable(const HPETComparator& comparator)
@ -288,11 +321,6 @@ void HPET::enable(const HPETComparator& comparator)
timer.capabilities = timer.capabilities | (u32)HPETFlags::TimerConfiguration::InterruptEnable;
}
u64 HPET::frequency() const
{
return m_frequency;
}
Vector<unsigned> HPET::capable_interrupt_numbers(const HPETComparator& comparator)
{
ASSERT(comparator.comparator_number() <= m_comparators.size());
@ -394,7 +422,7 @@ HPET::HPET(PhysicalAddress acpi_hpet)
klog() << "HPET: frequency " << m_frequency << " Hz (" << MEGAHERTZ_TO_HERTZ(m_frequency) << " MHz) resolution: " << calculate_ticks_in_nanoseconds() << "ns";
ASSERT(regs.capabilities.main_counter_tick_period <= ABSOLUTE_MAXIMUM_COUNTER_TICK_PERIOD);
// Reset the counter, just in case...
// Reset the counter, just in case... (needs to match m_main_counter_last_read)
regs.main_counter_value.high = 0;
regs.main_counter_value.low = 0;
if (regs.capabilities.attributes & (u32)HPETFlags::Attributes::LegacyReplacementRouteCapable)