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[kernel] Add new threads to different CPUs

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Previously, when adding a new thread, we only ever added it to the
current CPU and relied on work stealing to balance the CPUs. This commit
has the scheduler schedule new tasks round-robin across CPUs in hopes of
having to steal fewer tasks.

Also adds the run_queue.prev pointer for debugging what task was just
running on the given CPU.
This commit is contained in:
Justin C. Miller
2022-03-13 18:07:08 -07:00
parent bb0d30610e
commit d759aae318
2 changed files with 11 additions and 6 deletions
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11
src/kernel/scheduler.cpp
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@@ -29,6 +29,7 @@ scheduler *scheduler::s_instance = nullptr;
struct run_queue
{
tcb_node *current = nullptr;
tcb_node *prev = nullptr;
tcb_list ready[scheduler::num_priorities];
tcb_list blocked;
@@ -38,7 +39,7 @@ struct run_queue
};
scheduler::scheduler(unsigned cpus) :
m_next_pid {1}
m_add_index {0}
{
kassert(!s_instance, "Created multiple schedulers!");
if (!s_instance)
@@ -108,11 +109,11 @@ scheduler::start()
void
scheduler::add_thread(TCB *t)
{
cpu_data &cpu = current_cpu();
run_queue &queue = m_run_queues[cpu.index];
cpu_data *cpu = g_cpu_data[m_add_index++ % g_num_cpus];
run_queue &queue = m_run_queues[cpu->index];
util::scoped_lock lock {queue.lock};
t->cpu = &cpu;
t->cpu = cpu;
t->time_left = quantum(t->priority);
queue.blocked.push_back(static_cast<tcb_node*>(t));
}
@@ -232,6 +233,7 @@ scheduler::steal_work(cpu_data &cpu)
stolen += balance_lists(my_queue.ready[pri], other_queue.ready[pri], cpu);
stolen += balance_lists(my_queue.blocked, other_queue.blocked, cpu);
other_queue_lock.release();
if (stolen)
log::debug(logs::sched, "CPU%02x stole %2d tasks from CPU%02x",
@@ -313,6 +315,7 @@ scheduler::schedule()
return;
}
queue.prev = queue.current;
thread *next_thread = next->thread;
cpu.thread = next_thread;