So no, this doesn't have a change in hell of making it.
On Thu, Jul 27, 2017 at 11:30:10AM -0400, Johannes Weiner wrote:
> +static void domain_cpu_update(struct memdelay_domain *md, int cpu,
> + int old, int new)
> +{
> + enum memdelay_domain_state state;
> + struct memdelay_domain_cpu *mdc;
> + unsigned long now, delta;
> + unsigned long flags;
> +
> + mdc = per_cpu_ptr(md->mdcs, cpu);
> + spin_lock_irqsave(&mdc->lock, flags);
Afaict this is inside scheduler locks, this cannot be a spinlock. Also,
do we really want to add more atomics there?
> + if (old) {
> + WARN_ONCE(!mdc->tasks[old], "cpu=%d old=%d new=%d counter=%d\n",
> + cpu, old, new, mdc->tasks[old]);
> + mdc->tasks[old] -= 1;
> + }
> + if (new)
> + mdc->tasks[new] += 1;
> +
> + /*
> + * The domain is somewhat delayed when a number of tasks are
> + * delayed but there are still others running the workload.
> + *
> + * The domain is fully delayed when all non-idle tasks on the
> + * CPU are delayed, or when a delayed task is actively running
> + * and preventing productive tasks from making headway.
> + *
> + * The state times then add up over all CPUs in the domain: if
> + * the domain is fully blocked on one CPU and there is another
> + * one running the workload, the domain is considered fully
> + * blocked 50% of the time.
> + */
> + if (!mdc->tasks[MTS_DELAYED_ACTIVE] && !mdc->tasks[MTS_DELAYED])
> + state = MDS_NONE;
> + else if (mdc->tasks[MTS_WORKING])
> + state = MDS_SOME;
> + else
> + state = MDS_FULL;
> +
> + if (mdc->state == state)
> + goto unlock;
> +
> + now = ktime_to_ns(ktime_get());
ktime_get_ns(), also no ktime in scheduler code.
> + delta = now - mdc->state_start;
> +
> + domain_move_clock(md);
> + md->times[mdc->state] += delta;
> +
> + mdc->state = state;
> + mdc->state_start = now;
> +unlock:
> + spin_unlock_irqrestore(&mdc->lock, flags);
> +}
> +
> +static struct memdelay_domain *memcg_domain(struct mem_cgroup *memcg)
> +{
> +#ifdef CONFIG_MEMCG
> + if (!mem_cgroup_disabled())
> + return memcg->memdelay_domain;
> +#endif
> + return &memdelay_global_domain;
> +}
> +
> +/**
> + * memdelay_task_change - note a task changing its delay/work state
> + * @task: the task changing state
> + * @delayed: 1 when task enters delayed state, -1 when it leaves
> + * @working: 1 when task enters working state, -1 when it leaves
> + * @active_delay: 1 when task enters active delay, -1 when it leaves
> + *
> + * Updates the task's domain counters to reflect a change in the
> + * task's delayed/working state.
> + */
> +void memdelay_task_change(struct task_struct *task, int old, int new)
> +{
> + int cpu = task_cpu(task);
> + struct mem_cgroup *memcg;
> + unsigned long delay = 0;
> +
> +#ifdef CONFIG_DEBUG_VM
> + WARN_ONCE(task->memdelay_state != old,
> + "cpu=%d task=%p state=%d (in_iowait=%d PF_MEMDELAYED=%d)
> old=%d new=%d\n",
> + cpu, task, task->memdelay_state, task->in_iowait,
> + !!(task->flags & PF_MEMDELAY), old, new);
> + task->memdelay_state = new;
> +#endif
> +
> + /* Account when tasks are entering and leaving delays */
> + if (old < MTS_DELAYED && new >= MTS_DELAYED) {
> + task->memdelay_start = ktime_to_ms(ktime_get());
> + } else if (old >= MTS_DELAYED && new < MTS_DELAYED) {
> + delay = ktime_to_ms(ktime_get()) - task->memdelay_start;
> + task->memdelay_total += delay;
> + }
Scheduler stuff will _NOT_ user ktime_get() and will _NOT_ do pointless
divisions into ms.
> +
> + /* Account domain state changes */
> + rcu_read_lock();
> + memcg = mem_cgroup_from_task(task);
> + do {
> + struct memdelay_domain *md;
> +
> + md = memcg_domain(memcg);
> + md->aggregate += delay;
> + domain_cpu_update(md, cpu, old, new);
> + } while (memcg && (memcg = parent_mem_cgroup(memcg)));
> + rcu_read_unlock();
We are _NOT_ going to do a 3rd cgroup iteration for every task action.
> +};
