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[kernel] Update scheduler policies

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A few updates to scheduler policies:
* Grant processes a startup timeslice bonus for time spent loading the
  process
* Grant processes a small fraction of a timeslice for yielding the CPU
  with time left
This commit is contained in:
Justin C. Miller
2020-06-28 17:50:29 -07:00
parent 6c468a134b
commit 0a28d2db07
3 changed files with 21 additions and 8 deletions
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24
src/kernel/scheduler.cpp
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@@ -1,4 +1,5 @@
#include "apic.h"
#include "clock.h"
#include "console.h"
#include "cpu.h"
#include "debug.h"
@@ -122,7 +123,11 @@ scheduler::create_process(pid_t pid)
auto *proc = new process_node;
proc->pid = pid ? pid : m_next_pid++;
proc->priority = default_priority;
proc->time_left = quantum(default_priority);
proc->time_left = quantum(default_priority) + startup_bonus;
log::debug(logs::task, "Creating process %d, priority %d, time slice %d",
proc->pid, proc->priority, proc->time_left);
return proc;
}
@@ -213,7 +218,7 @@ scheduler::start()
log::info(logs::task, "Starting scheduler.");
wrmsr(msr::ia32_gs_base, reinterpret_cast<uintptr_t>(&bsp_cpu_data));
m_apic->enable_timer(isr::isrTimer, false);
schedule();
m_apic->reset_timer(10);
}
void scheduler::prune(uint64_t now)
@@ -302,6 +307,11 @@ scheduler::schedule()
log::debug(logs::task, "Scheduler demoting process %d, priority %d",
m_current->pid, m_current->priority);
m_current->time_left = quantum(m_current->priority);
} else if (remaining > 0) {
// Process gave up CPU, give it a small bonus to its
// remaining timeslice.
uint32_t bonus = quantum(priority) >> 4;
m_current->time_left += bonus;
}
m_runlists[priority].remove(m_current);
@@ -321,17 +331,17 @@ scheduler::schedule()
}
m_current->last_ran = m_clock;
m_current = m_runlists[priority].pop_front();
m_current->last_ran = m_clock;
m_apic->reset_timer(m_current->time_left);
if (lastpid != m_current->pid) {
task_switch(m_current);
bool loading = m_current->flags && process_flags::loading;
log::debug(logs::task, "Scheduler switched to process %d, priority %d @ %lld.",
m_current->pid, m_current->priority, m_clock);
log::debug(logs::task, "Scheduler switched to process %d, priority %d time left %d @ %lld.",
m_current->pid, m_current->priority, m_current->time_left, m_clock);
}
m_apic->reset_timer(m_current->time_left);
}
process_node *