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[kernel] Change to one-shot timer scheduler

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Instead of many timer interrupts and decrementing a process' remaining
quanta, change to setting a single timer for when a process should be
preempted. If it uses its whole timeslice, demote it. If it uses less
than half before blocking, promote it. Determine timeslice based on
priority as well.

This change also required changing the apic timer interface to be purely
interval (in microseconds) based instead of its previous interval/tick
hybrid.
This commit is contained in:
Justin C. Miller
2020-06-03 20:56:59 -07:00
parent ea1224e213
commit a10aca573d
7 changed files with 125 additions and 77 deletions
Download Patch File Download Diff File Expand all files Collapse all files

84
src/kernel/apic.cpp
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@@ -5,6 +5,15 @@
#include "log.h"
#include "page_manager.h"
static constexpr uint16_t lapic_spurious = 0x00f0;
static constexpr uint16_t lapic_lvt_timer = 0x0320;
static constexpr uint16_t lapic_lvt_lint0 = 0x0350;
static constexpr uint16_t lapic_lvt_lint1 = 0x0360;
static constexpr uint16_t lapic_timer_init = 0x0380;
static constexpr uint16_t lapic_timer_cur = 0x0390;
static constexpr uint16_t lapic_timer_div = 0x03e0;
static uint32_t
apic_read(uint32_t volatile *apic, uint16_t offset)
@@ -44,9 +53,10 @@ apic::apic(uint32_t *base) :
lapic::lapic(uint32_t *base, isr spurious) :
apic(base)
apic(base),
m_divisor(0)
{
apic_write(m_base, 0xf0, static_cast<uint32_t>(spurious));
apic_write(m_base, lapic_spurious, static_cast<uint32_t>(spurious));
log::info(logs::apic, "LAPIC created, base %lx", m_base);
}
@@ -62,7 +72,9 @@ lapic::calibrate_timer()
outb(0x43, command);
const uint32_t initial = -1u;
enable_timer_internal(isr::isrSpurious, 1, initial, false);
enable_timer(isr::isrSpurious);
set_divisor(1);
apic_write(m_base, lapic_timer_init, initial);
const int iterations = 5;
for (int i=0; i<iterations; ++i) {
@@ -81,16 +93,16 @@ lapic::calibrate_timer()
}
}
uint32_t remain = stop_timer();
uint32_t ticks_total = initial - remain;
uint32_t remaining = apic_read(m_base, lapic_timer_cur);
uint32_t ticks_total = initial - remaining;
m_ticks_per_us = ticks_total / (iterations * 33000);
log::info(logs::apic, "APIC timer ticks %d times per nanosecond.", m_ticks_per_us);
interrupts_enable();
}
uint32_t
lapic::enable_timer_internal(isr vector, uint8_t divisor, uint32_t count, bool repeat)
void
lapic::set_divisor(uint8_t divisor)
{
uint32_t divbits = 0;
@@ -107,39 +119,45 @@ lapic::enable_timer_internal(isr vector, uint8_t divisor, uint32_t count, bool r
kassert(0, "Invalid divisor passed to lapic::enable_timer");
}
uint32_t lvte = static_cast<uint8_t>(vector);
if (repeat)
lvte |= 0x20000;
apic_write(m_base, lapic_timer_div, divbits);
m_divisor = divisor;
}
log::debug(logs::apic, "Enabling APIC timer count %ld, divisor %d, isr %02x",
count, divisor, vector);
apic_write(m_base, 0x320, lvte);
apic_write(m_base, 0x3e0, divbits);
uint32_t
lapic::enable_timer_internal(isr vector, uint8_t divisor, uint32_t count, bool repeat)
{
reset_timer(count);
return count;
}
uint32_t
lapic::enable_timer(isr vector, uint64_t interval, bool repeat)
void
lapic::enable_timer(isr vector, bool repeat)
{
uint64_t ticks = interval * m_ticks_per_us;
uint32_t lvte = static_cast<uint8_t>(vector);
if (repeat)
lvte |= 0x20000;
apic_write(m_base, lapic_lvt_timer, lvte);
int divisor = 1;
while (ticks > -1u) {
ticks /= 2;
divisor *= 2;
}
return enable_timer_internal(vector, divisor, static_cast<uint32_t>(ticks), repeat);
log::debug(logs::apic, "Enabling APIC timer at isr %02x", vector);
}
uint32_t
lapic::reset_timer(uint32_t count)
lapic::reset_timer(uint64_t interval)
{
uint32_t remaining = apic_read(m_base, 0x390);
apic_write(m_base, 0x380, count);
uint64_t remaining = ticks_to_us(apic_read(m_base, lapic_timer_cur));
uint64_t ticks = us_to_ticks(interval);
int divisor = 1;
while (ticks > 0xffffffffull) {
ticks >>= 1;
divisor <<= 1;
}
if (divisor != m_divisor)
set_divisor(divisor);
apic_write(m_base, lapic_timer_init, ticks);
return remaining;
}
@@ -148,7 +166,7 @@ lapic::enable_lint(uint8_t num, isr vector, bool nmi, uint16_t flags)
{
kassert(num == 0 || num == 1, "Invalid LINT passed to lapic::enable_lint.");
uint16_t off = num ? 0x360 : 0x350;
uint16_t off = num ? lapic_lvt_lint1 : lapic_lvt_lint0;
uint32_t lvte = static_cast<uint8_t>(vector);
uint16_t polarity = flags & 0x3;
@@ -169,16 +187,16 @@ lapic::enable_lint(uint8_t num, isr vector, bool nmi, uint16_t flags)
void
lapic::enable()
{
apic_write(m_base, 0xf0,
apic_read(m_base, 0xf0) | 0x100);
apic_write(m_base, lapic_spurious,
apic_read(m_base, lapic_spurious) | 0x100);
log::debug(logs::apic, "LAPIC enabled!");
}
void
lapic::disable()
{
apic_write(m_base, 0xf0,
apic_read(m_base, 0xf0) & ~0x100);
apic_write(m_base, lapic_spurious,
apic_read(m_base, lapic_spurious) & ~0x100);
log::debug(logs::apic, "LAPIC disabled.");
}