psi: cgroup support

On a system that executes multiple cgrouped jobs and independent
workloads, we don't just care about the health of the overall system, but
also that of individual jobs, so that we can ensure individual job health,
fairness between jobs, or prioritize some jobs over others.

This patch implements pressure stall tracking for cgroups.  In kernels
with CONFIG_PSI=y, cgroup2 groups will have cpu.pressure, memory.pressure,
and io.pressure files that track aggregate pressure stall times for only
the tasks inside the cgroup.

Link: http://lkml.kernel.org/r/20180828172258.3185-10-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Daniel Drake <drake@endlessm.com>
Tested-by: Suren Baghdasaryan <surenb@google.com>
Cc: Christopher Lameter <cl@linux.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <jweiner@fb.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Enderborg <peter.enderborg@sony.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 110 insertions, 8 deletions

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 595414599b98..7cdecfc010af 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -473,9 +473,35 @@ static void psi_group_change(struct psi_group *group, int cpu,
 		schedule_delayed_work(&group->clock_work, PSI_FREQ);
 }
 
+static struct psi_group *iterate_groups(struct task_struct *task, void **iter)
+{
+#ifdef CONFIG_CGROUPS
+	struct cgroup *cgroup = NULL;
+
+	if (!*iter)
+		cgroup = task->cgroups->dfl_cgrp;
+	else if (*iter == &psi_system)
+		return NULL;
+	else
+		cgroup = cgroup_parent(*iter);
+
+	if (cgroup && cgroup_parent(cgroup)) {
+		*iter = cgroup;
+		return cgroup_psi(cgroup);
+	}
+#else
+	if (*iter)
+		return NULL;
+#endif
+	*iter = &psi_system;
+	return &psi_system;
+}
+
 void psi_task_change(struct task_struct *task, int clear, int set)
 {
 	int cpu = task_cpu(task);
+	struct psi_group *group;
+	void *iter = NULL;
 
 	if (!task->pid)
 		return;
@@ -492,17 +518,23 @@ void psi_task_change(struct task_struct *task, int clear, int set)
 	task->psi_flags &= ~clear;
 	task->psi_flags |= set;
 
-	psi_group_change(&psi_system, cpu, clear, set);
+	while ((group = iterate_groups(task, &iter)))
+		psi_group_change(group, cpu, clear, set);
 }
 
 void psi_memstall_tick(struct task_struct *task, int cpu)
 {
-	struct psi_group_cpu *groupc;
+	struct psi_group *group;
+	void *iter = NULL;
 
-	groupc = per_cpu_ptr(psi_system.pcpu, cpu);
-	write_seqcount_begin(&groupc->seq);
-	record_times(groupc, cpu, true);
-	write_seqcount_end(&groupc->seq);
+	while ((group = iterate_groups(task, &iter))) {
+		struct psi_group_cpu *groupc;
+
+		groupc = per_cpu_ptr(group->pcpu, cpu);
+		write_seqcount_begin(&groupc->seq);
+		record_times(groupc, cpu, true);
+		write_seqcount_end(&groupc->seq);
+	}
 }
 
 /**
@@ -565,8 +597,78 @@ void psi_memstall_leave(unsigned long *flags)
 	rq_unlock_irq(rq, &rf);
 }
 
-static int psi_show(struct seq_file *m, struct psi_group *group,
-		    enum psi_res res)
+#ifdef CONFIG_CGROUPS
+int psi_cgroup_alloc(struct cgroup *cgroup)
+{
+	if (psi_disabled)
+		return 0;
+
+	cgroup->psi.pcpu = alloc_percpu(struct psi_group_cpu);
+	if (!cgroup->psi.pcpu)
+		return -ENOMEM;
+	group_init(&cgroup->psi);
+	return 0;
+}
+
+void psi_cgroup_free(struct cgroup *cgroup)
+{
+	if (psi_disabled)
+		return;
+
+	cancel_delayed_work_sync(&cgroup->psi.clock_work);
+	free_percpu(cgroup->psi.pcpu);
+}
+
+/**
+ * cgroup_move_task - move task to a different cgroup
+ * @task: the task
+ * @to: the target css_set
+ *
+ * Move task to a new cgroup and safely migrate its associated stall
+ * state between the different groups.
+ *
+ * This function acquires the task's rq lock to lock out concurrent
+ * changes to the task's scheduling state and - in case the task is
+ * running - concurrent changes to its stall state.
+ */
+void cgroup_move_task(struct task_struct *task, struct css_set *to)
+{
+	bool move_psi = !psi_disabled;
+	unsigned int task_flags = 0;
+	struct rq_flags rf;
+	struct rq *rq;
+
+	if (move_psi) {
+		rq = task_rq_lock(task, &rf);
+
+		if (task_on_rq_queued(task))
+			task_flags = TSK_RUNNING;
+		else if (task->in_iowait)
+			task_flags = TSK_IOWAIT;
+
+		if (task->flags & PF_MEMSTALL)
+			task_flags |= TSK_MEMSTALL;
+
+		if (task_flags)
+			psi_task_change(task, task_flags, 0);
+	}
+
+	/*
+	 * Lame to do this here, but the scheduler cannot be locked
+	 * from the outside, so we move cgroups from inside sched/.
+	 */
+	rcu_assign_pointer(task->cgroups, to);
+
+	if (move_psi) {
+		if (task_flags)
+			psi_task_change(task, 0, task_flags);
+
+		task_rq_unlock(rq, task, &rf);
+	}
+}
+#endif /* CONFIG_CGROUPS */
+
+int psi_show(struct seq_file *m, struct psi_group *group, enum psi_res res)
 {
 	int full;