On Thu, Jul 12, 2018 at 01:29:40PM -0400, Johannes Weiner wrote:
> +static void time_state(struct psi_resource *res, int state, u64 now)
> +{
> + if (res->state != PSI_NONE) {
> + bool was_full = res->state == PSI_FULL;
> +
> + res->times[was_full] += now - res->state_start;
> + }
> + if (res->state != state)
> + res->state = state;
> + if (res->state != PSI_NONE)
> + res->state_start = now;
> +}
> +
> +static void psi_group_change(struct psi_group *group, int cpu, u64 now,
> + unsigned int clear, unsigned int set)
> +{
> + enum psi_state state = PSI_NONE;
> + struct psi_group_cpu *groupc;
> + unsigned int *tasks;
> + unsigned int to, bo;
> +
> + groupc = per_cpu_ptr(group->cpus, cpu);
> + tasks = groupc->tasks;
> +
> + /* Update task counts according to the set/clear bitmasks */
> + for (to = 0; (bo = ffs(clear)); to += bo, clear >>= bo) {
> + int idx = to + (bo - 1);
> +
> + if (tasks[idx] == 0 && !psi_bug) {
> + printk_deferred(KERN_ERR "psi: task underflow! cpu=%d
> idx=%d tasks=[%u %u %u] clear=%x set=%x\n",
> + cpu, idx, tasks[0], tasks[1], tasks[2],
> + clear, set);
> + psi_bug = 1;
> + }
> + tasks[idx]--;
> + }
> + for (to = 0; (bo = ffs(set)); to += bo, set >>= bo)
> + tasks[to + (bo - 1)]++;
> +
> + /* Time in which tasks wait for the CPU */
> + state = PSI_NONE;
> + if (tasks[NR_RUNNING] > 1)
> + state = PSI_SOME;
> + time_state(&groupc->res[PSI_CPU], state, now);
> +
> + /* Time in which tasks wait for memory */
> + state = PSI_NONE;
> + if (tasks[NR_MEMSTALL]) {
> + if (!tasks[NR_RUNNING] ||
> + (cpu_curr(cpu)->flags & PF_MEMSTALL))
> + state = PSI_FULL;
> + else
> + state = PSI_SOME;
> + }
> + time_state(&groupc->res[PSI_MEM], state, now);
> +
> + /* Time in which tasks wait for IO */
> + state = PSI_NONE;
> + if (tasks[NR_IOWAIT]) {
> + if (!tasks[NR_RUNNING])
> + state = PSI_FULL;
> + else
> + state = PSI_SOME;
> + }
> + time_state(&groupc->res[PSI_IO], state, now);
> +
> + /* Time in which tasks are non-idle, to weigh the CPU in summaries */
> + if (groupc->nonidle)
> + groupc->nonidle_time += now - groupc->nonidle_start;
> + groupc->nonidle = tasks[NR_RUNNING] ||
> + tasks[NR_IOWAIT] || tasks[NR_MEMSTALL];
> + if (groupc->nonidle)
> + groupc->nonidle_start = now;
> +
> + /* Kick the stats aggregation worker if it's gone to sleep */
> + if (!delayed_work_pending(&group->clock_work))
> + schedule_delayed_work(&group->clock_work, PSI_FREQ);
> +}
> +
> +void psi_task_change(struct task_struct *task, u64 now, int clear, int set)
> +{
> + int cpu = task_cpu(task);
> +
> + if (psi_disabled)
> + return;
> +
> + if (!task->pid)
> + return;
> +
> + if (((task->psi_flags & set) ||
> + (task->psi_flags & clear) != clear) &&
> + !psi_bug) {
> + printk_deferred(KERN_ERR "psi: inconsistent task state!
> task=%d:%s cpu=%d psi_flags=%x clear=%x set=%x\n",
> + task->pid, task->comm, cpu,
> + task->psi_flags, clear, set);
> + psi_bug = 1;
> + }
> +
> + task->psi_flags &= ~clear;
> + task->psi_flags |= set;
> +
> + psi_group_change(&psi_system, cpu, now, clear, set);
> +}
> +/*
> + * PSI tracks state that persists across sleeps, such as iowaits and
> + * memory stalls. As a result, it has to distinguish between sleeps,
> + * where a task's runnable state changes, and requeues, where a task
> + * and its state are being moved between CPUs and runqueues.
> + */
> +static inline void psi_enqueue(struct task_struct *p, u64 now, bool wakeup)
> +{
> + int clear = 0, set = TSK_RUNNING;
> +
> + if (psi_disabled)
> + return;
> +
> + if (!wakeup || p->sched_psi_wake_requeue) {
> + if (p->flags & PF_MEMSTALL)
> + set |= TSK_MEMSTALL;
> + if (p->sched_psi_wake_requeue)
> + p->sched_psi_wake_requeue = 0;
> + } else {
> + if (p->in_iowait)
> + clear |= TSK_IOWAIT;
> + }
> +
> + psi_task_change(p, now, clear, set);
> +}
> +
> +static inline void psi_dequeue(struct task_struct *p, u64 now, bool sleep)
> +{
> + int clear = TSK_RUNNING, set = 0;
> +
> + if (psi_disabled)
> + return;
> +
> + if (!sleep) {
> + if (p->flags & PF_MEMSTALL)
> + clear |= TSK_MEMSTALL;
> + } else {
> + if (p->in_iowait)
> + set |= TSK_IOWAIT;
> + }
> +
> + psi_task_change(p, now, clear, set);
> +}
This is still a scary amount of accounting; not to mention you'll be
adding O(cgroup-depth) to this in a later patch.
Where are the performance numbers for all this?
