Merge branch 'akpm' (patches from Andrew)

Merge updates from Andrew Morton:

 - a few misc things

 - ocfs2 updates

 - most of MM

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (132 commits)
  hugetlbfs: dirty pages as they are added to pagecache
  mm: export add_swap_extent()
  mm: split SWP_FILE into SWP_ACTIVATED and SWP_FS
  tools/testing/selftests/vm/map_fixed_noreplace.c: add test for MAP_FIXED_NOREPLACE
  mm: thp: relocate flush_cache_range() in migrate_misplaced_transhuge_page()
  mm: thp: fix mmu_notifier in migrate_misplaced_transhuge_page()
  mm: thp: fix MADV_DONTNEED vs migrate_misplaced_transhuge_page race condition
  mm/kasan/quarantine.c: make quarantine_lock a raw_spinlock_t
  mm/gup: cache dev_pagemap while pinning pages
  Revert "x86/e820: put !E820_TYPE_RAM regions into memblock.reserved"
  mm: return zero_resv_unavail optimization
  mm: zero remaining unavailable struct pages
  tools/testing/selftests/vm/gup_benchmark.c: add MAP_HUGETLB option
  tools/testing/selftests/vm/gup_benchmark.c: add MAP_SHARED option
  tools/testing/selftests/vm/gup_benchmark.c: allow user specified file
  tools/testing/selftests/vm/gup_benchmark.c: fix 'write' flag usage
  mm/gup_benchmark.c: add additional pinning methods
  mm/gup_benchmark.c: time put_page()
  mm: don't raise MEMCG_OOM event due to failed high-order allocation
  mm/page-writeback.c: fix range_cyclic writeback vs writepages deadlock
  ...

11 files changed, 1137 insertions, 193 deletions

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 4c1cf0969a80..8b79318810ad 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -55,6 +55,7 @@
 #include <linux/nsproxy.h>
 #include <linux/file.h>
 #include <linux/sched/cputime.h>
+#include <linux/psi.h>
 #include <net/sock.h>
 
 #define CREATE_TRACE_POINTS
@@ -862,7 +863,7 @@ static void css_set_move_task(struct task_struct *task,
 		 */
 		WARN_ON_ONCE(task->flags & PF_EXITING);
 
-		rcu_assign_pointer(task->cgroups, to_cset);
+		cgroup_move_task(task, to_cset);
 		list_add_tail(&task->cg_list, use_mg_tasks ? &to_cset->mg_tasks :
 							     &to_cset->tasks);
 	}
@@ -3446,6 +3447,21 @@ static int cpu_stat_show(struct seq_file *seq, void *v)
 	return ret;
 }
 
+#ifdef CONFIG_PSI
+static int cgroup_io_pressure_show(struct seq_file *seq, void *v)
+{
+	return psi_show(seq, &seq_css(seq)->cgroup->psi, PSI_IO);
+}
+static int cgroup_memory_pressure_show(struct seq_file *seq, void *v)
+{
+	return psi_show(seq, &seq_css(seq)->cgroup->psi, PSI_MEM);
+}
+static int cgroup_cpu_pressure_show(struct seq_file *seq, void *v)
+{
+	return psi_show(seq, &seq_css(seq)->cgroup->psi, PSI_CPU);
+}
+#endif
+
 static int cgroup_file_open(struct kernfs_open_file *of)
 {
 	struct cftype *cft = of->kn->priv;
@@ -4576,6 +4592,23 @@ static struct cftype cgroup_base_files[] = {
 		.flags = CFTYPE_NOT_ON_ROOT,
 		.seq_show = cpu_stat_show,
 	},
+#ifdef CONFIG_PSI
+	{
+		.name = "io.pressure",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.seq_show = cgroup_io_pressure_show,
+	},
+	{
+		.name = "memory.pressure",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.seq_show = cgroup_memory_pressure_show,
+	},
+	{
+		.name = "cpu.pressure",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.seq_show = cgroup_cpu_pressure_show,
+	},
+#endif
 	{ }	/* terminate */
 };
 
@@ -4636,6 +4669,7 @@ static void css_free_rwork_fn(struct work_struct *work)
 			 */
 			cgroup_put(cgroup_parent(cgrp));
 			kernfs_put(cgrp->kn);
+			psi_cgroup_free(cgrp);
 			if (cgroup_on_dfl(cgrp))
 				cgroup_rstat_exit(cgrp);
 			kfree(cgrp);
@@ -4892,10 +4926,15 @@ static struct cgroup *cgroup_create(struct cgroup *parent)
 	cgrp->self.parent = &parent->self;
 	cgrp->root = root;
 	cgrp->level = level;
-	ret = cgroup_bpf_inherit(cgrp);
+
+	ret = psi_cgroup_alloc(cgrp);
 	if (ret)
 		goto out_idr_free;
 
+	ret = cgroup_bpf_inherit(cgrp);
+	if (ret)
+		goto out_psi_free;
+
 	for (tcgrp = cgrp; tcgrp; tcgrp = cgroup_parent(tcgrp)) {
 		cgrp->ancestor_ids[tcgrp->level] = tcgrp->id;
 
@@ -4933,6 +4972,8 @@ static struct cgroup *cgroup_create(struct cgroup *parent)
 
 	return cgrp;
 
+out_psi_free:
+	psi_cgroup_free(cgrp);
 out_idr_free:
 	cgroup_idr_remove(&root->cgroup_idr, cgrp->id);
 out_stat_exit:
diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c
index 2ddfce8f1e8f..bb4fe4e1a601 100644
--- a/kernel/debug/kdb/kdb_main.c
+++ b/kernel/debug/kdb/kdb_main.c
@@ -2556,16 +2556,11 @@ static int kdb_summary(int argc, const char **argv)
 	}
 	kdb_printf("%02ld:%02ld\n", val.uptime/(60*60), (val.uptime/60)%60);
 
-	/* lifted from fs/proc/proc_misc.c::loadavg_read_proc() */
-
-#define LOAD_INT(x) ((x) >> FSHIFT)
-#define LOAD_FRAC(x) LOAD_INT(((x) & (FIXED_1-1)) * 100)
 	kdb_printf("load avg   %ld.%02ld %ld.%02ld %ld.%02ld\n",
 		LOAD_INT(val.loads[0]), LOAD_FRAC(val.loads[0]),
 		LOAD_INT(val.loads[1]), LOAD_FRAC(val.loads[1]),
 		LOAD_INT(val.loads[2]), LOAD_FRAC(val.loads[2]));
-#undef LOAD_INT
-#undef LOAD_FRAC
+
 	/* Display in kilobytes */
 #define K(x) ((x) << (PAGE_SHIFT - 10))
 	kdb_printf("\nMemTotal:       %8lu kB\nMemFree:        %8lu kB\n"
diff --git a/kernel/delayacct.c b/kernel/delayacct.c
index ca8ac2824f0b..2a12b988c717 100644
--- a/kernel/delayacct.c
+++ b/kernel/delayacct.c
@@ -135,9 +135,12 @@ int __delayacct_add_tsk(struct taskstats *d, struct task_struct *tsk)
 	d->swapin_delay_total = (tmp < d->swapin_delay_total) ? 0 : tmp;
 	tmp = d->freepages_delay_total + tsk->delays->freepages_delay;
 	d->freepages_delay_total = (tmp < d->freepages_delay_total) ? 0 : tmp;
+	tmp = d->thrashing_delay_total + tsk->delays->thrashing_delay;
+	d->thrashing_delay_total = (tmp < d->thrashing_delay_total) ? 0 : tmp;
 	d->blkio_count += tsk->delays->blkio_count;
 	d->swapin_count += tsk->delays->swapin_count;
 	d->freepages_count += tsk->delays->freepages_count;
+	d->thrashing_count += tsk->delays->thrashing_count;
 	raw_spin_unlock_irqrestore(&tsk->delays->lock, flags);
 
 	return 0;
@@ -169,3 +172,15 @@ void __delayacct_freepages_end(void)
 		&current->delays->freepages_count);
 }
 
+void __delayacct_thrashing_start(void)
+{
+	current->delays->thrashing_start = ktime_get_ns();
+}
+
+void __delayacct_thrashing_end(void)
+{
+	delayacct_end(&current->delays->lock,
+		      &current->delays->thrashing_start,
+		      &current->delays->thrashing_delay,
+		      &current->delays->thrashing_count);
+}
diff --git a/kernel/fork.c b/kernel/fork.c
index f0b58479534f..8f82a3bdcb8f 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -223,9 +223,14 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
 		return s->addr;
 	}
 
+	/*
+	 * Allocated stacks are cached and later reused by new threads,
+	 * so memcg accounting is performed manually on assigning/releasing
+	 * stacks to tasks. Drop __GFP_ACCOUNT.
+	 */
 	stack = __vmalloc_node_range(THREAD_SIZE, THREAD_ALIGN,
 				     VMALLOC_START, VMALLOC_END,
-				     THREADINFO_GFP,
+				     THREADINFO_GFP & ~__GFP_ACCOUNT,
 				     PAGE_KERNEL,
 				     0, node, __builtin_return_address(0));
 
@@ -248,9 +253,19 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
 static inline void free_thread_stack(struct task_struct *tsk)
 {
 #ifdef CONFIG_VMAP_STACK
-	if (task_stack_vm_area(tsk)) {
+	struct vm_struct *vm = task_stack_vm_area(tsk);
+
+	if (vm) {
 		int i;
 
+		for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
+			mod_memcg_page_state(vm->pages[i],
+					     MEMCG_KERNEL_STACK_KB,
+					     -(int)(PAGE_SIZE / 1024));
+
+			memcg_kmem_uncharge(vm->pages[i], 0);
+		}
+
 		for (i = 0; i < NR_CACHED_STACKS; i++) {
 			if (this_cpu_cmpxchg(cached_stacks[i],
 					NULL, tsk->stack_vm_area) != NULL)
@@ -351,10 +366,6 @@ static void account_kernel_stack(struct task_struct *tsk, int account)
 					    NR_KERNEL_STACK_KB,
 					    PAGE_SIZE / 1024 * account);
 		}
-
-		/* All stack pages belong to the same memcg. */
-		mod_memcg_page_state(vm->pages[0], MEMCG_KERNEL_STACK_KB,
-				     account * (THREAD_SIZE / 1024));
 	} else {
 		/*
 		 * All stack pages are in the same zone and belong to the
@@ -370,6 +381,35 @@ static void account_kernel_stack(struct task_struct *tsk, int account)
 	}
 }
 
+static int memcg_charge_kernel_stack(struct task_struct *tsk)
+{
+#ifdef CONFIG_VMAP_STACK
+	struct vm_struct *vm = task_stack_vm_area(tsk);
+	int ret;
+
+	if (vm) {
+		int i;
+
+		for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
+			/*
+			 * If memcg_kmem_charge() fails, page->mem_cgroup
+			 * pointer is NULL, and both memcg_kmem_uncharge()
+			 * and mod_memcg_page_state() in free_thread_stack()
+			 * will ignore this page. So it's safe.
+			 */
+			ret = memcg_kmem_charge(vm->pages[i], GFP_KERNEL, 0);
+			if (ret)
+				return ret;
+
+			mod_memcg_page_state(vm->pages[i],
+					     MEMCG_KERNEL_STACK_KB,
+					     PAGE_SIZE / 1024);
+		}
+	}
+#endif
+	return 0;
+}
+
 static void release_task_stack(struct task_struct *tsk)
 {
 	if (WARN_ON(tsk->state != TASK_DEAD))
@@ -807,6 +847,9 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
 	if (!stack)
 		goto free_tsk;
 
+	if (memcg_charge_kernel_stack(tsk))
+		goto free_stack;
+
 	stack_vm_area = task_stack_vm_area(tsk);
 
 	err = arch_dup_task_struct(tsk, orig);
@@ -1779,6 +1822,10 @@ static __latent_entropy struct task_struct *copy_process(
 
 	p->default_timer_slack_ns = current->timer_slack_ns;
 
+#ifdef CONFIG_PSI
+	p->psi_flags = 0;
+#endif
+
 	task_io_accounting_init(&p->ioac);
 	acct_clear_integrals(p);
 
diff --git a/kernel/memremap.c b/kernel/memremap.c
index 5b8600d39931..620fc4d2559a 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -175,10 +175,10 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 	struct vmem_altmap *altmap = pgmap->altmap_valid ?
 			&pgmap->altmap : NULL;
 	struct resource *res = &pgmap->res;
-	unsigned long pfn, pgoff, order;
+	struct dev_pagemap *conflict_pgmap;
 	pgprot_t pgprot = PAGE_KERNEL;
+	unsigned long pgoff, order;
 	int error, nid, is_ram;
-	struct dev_pagemap *conflict_pgmap;
 
 	align_start = res->start & ~(SECTION_SIZE - 1);
 	align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
@@ -256,19 +256,14 @@ void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
 	if (error)
 		goto err_add_memory;
 
-	for_each_device_pfn(pfn, pgmap) {
-		struct page *page = pfn_to_page(pfn);
-
-		/*
-		 * ZONE_DEVICE pages union ->lru with a ->pgmap back
-		 * pointer.  It is a bug if a ZONE_DEVICE page is ever
-		 * freed or placed on a driver-private list.  Seed the
-		 * storage with LIST_POISON* values.
-		 */
-		list_del(&page->lru);
-		page->pgmap = pgmap;
-		percpu_ref_get(pgmap->ref);
-	}
+	/*
+	 * Initialization of the pages has been deferred until now in order
+	 * to allow us to do the work while not holding the hotplug lock.
+	 */
+	memmap_init_zone_device(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
+				align_start >> PAGE_SHIFT,
+				align_size >> PAGE_SHIFT, pgmap);
+	percpu_ref_get_many(pgmap->ref, pfn_end(pgmap) - pfn_first(pgmap));
 
 	devm_add_action(dev, devm_memremap_pages_release, pgmap);
 
diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile
index 7fe183404c38..21fb5a5662b5 100644
--- a/kernel/sched/Makefile
+++ b/kernel/sched/Makefile
@@ -29,3 +29,4 @@ obj-$(CONFIG_CPU_FREQ) += cpufreq.o
 obj-$(CONFIG_CPU_FREQ_GOV_SCHEDUTIL) += cpufreq_schedutil.o
 obj-$(CONFIG_MEMBARRIER) += membarrier.o
 obj-$(CONFIG_CPU_ISOLATION) += isolation.o
+obj-$(CONFIG_PSI) += psi.o
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2e696b03e99d..fd2fce8a001b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -722,8 +722,10 @@ static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
 	if (!(flags & ENQUEUE_NOCLOCK))
 		update_rq_clock(rq);
 
-	if (!(flags & ENQUEUE_RESTORE))
+	if (!(flags & ENQUEUE_RESTORE)) {
 		sched_info_queued(rq, p);
+		psi_enqueue(p, flags & ENQUEUE_WAKEUP);
+	}
 
 	p->sched_class->enqueue_task(rq, p, flags);
 }
@@ -733,8 +735,10 @@ static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags)
 	if (!(flags & DEQUEUE_NOCLOCK))
 		update_rq_clock(rq);
 
-	if (!(flags & DEQUEUE_SAVE))
+	if (!(flags & DEQUEUE_SAVE)) {
 		sched_info_dequeued(rq, p);
+		psi_dequeue(p, flags & DEQUEUE_SLEEP);
+	}
 
 	p->sched_class->dequeue_task(rq, p, flags);
 }
@@ -2037,6 +2041,7 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 	cpu = select_task_rq(p, p->wake_cpu, SD_BALANCE_WAKE, wake_flags);
 	if (task_cpu(p) != cpu) {
 		wake_flags |= WF_MIGRATED;
+		psi_ttwu_dequeue(p);
 		set_task_cpu(p, cpu);
 	}
 
@@ -3051,6 +3056,7 @@ void scheduler_tick(void)
 	curr->sched_class->task_tick(rq, curr, 0);
 	cpu_load_update_active(rq);
 	calc_global_load_tick(rq);
+	psi_task_tick(rq);
 
 	rq_unlock(rq, &rf);
 
@@ -4933,9 +4939,7 @@ static void do_sched_yield(void)
 	struct rq_flags rf;
 	struct rq *rq;
 
-	local_irq_disable();
-	rq = this_rq();
-	rq_lock(rq, &rf);
+	rq = this_rq_lock_irq(&rf);
 
 	schedstat_inc(rq->yld_count);
 	current->sched_class->yield_task(rq);
@@ -6069,6 +6073,8 @@ void __init sched_init(void)
 
 	init_schedstats();
 
+	psi_init();
+
 	scheduler_running = 1;
 }
 
diff --git a/kernel/sched/loadavg.c b/kernel/sched/loadavg.c
index a171c1258109..28a516575c18 100644
--- a/kernel/sched/loadavg.c
+++ b/kernel/sched/loadavg.c
@@ -91,19 +91,73 @@ long calc_load_fold_active(struct rq *this_rq, long adjust)
 	return delta;
 }
 
-/*
- * a1 = a0 * e + a * (1 - e)
+/**
+ * fixed_power_int - compute: x^n, in O(log n) time
+ *
+ * @x:         base of the power
+ * @frac_bits: fractional bits of @x
+ * @n:         power to raise @x to.
+ *
+ * By exploiting the relation between the definition of the natural power
+ * function: x^n := x*x*...*x (x multiplied by itself for n times), and
+ * the binary encoding of numbers used by computers: n := \Sum n_i * 2^i,
+ * (where: n_i \elem {0, 1}, the binary vector representing n),
+ * we find: x^n := x^(\Sum n_i * 2^i) := \Prod x^(n_i * 2^i), which is
+ * of course trivially computable in O(log_2 n), the length of our binary
+ * vector.
  */
 static unsigned long
-calc_load(unsigned long load, unsigned long exp, unsigned long active)
+fixed_power_int(unsigned long x, unsigned int frac_bits, unsigned int n)
 {
-	unsigned long newload;
+	unsigned long result = 1UL << frac_bits;
+
+	if (n) {
+		for (;;) {
+			if (n & 1) {
+				result *= x;
+				result += 1UL << (frac_bits - 1);
+				result >>= frac_bits;
+			}
+			n >>= 1;
+			if (!n)
+				break;
+			x *= x;
+			x += 1UL << (frac_bits - 1);
+			x >>= frac_bits;
+		}
+	}
 
-	newload = load * exp + active * (FIXED_1 - exp);
-	if (active >= load)
-		newload += FIXED_1-1;
+	return result;
+}
 
-	return newload / FIXED_1;
+/*
+ * a1 = a0 * e + a * (1 - e)
+ *
+ * a2 = a1 * e + a * (1 - e)
+ *    = (a0 * e + a * (1 - e)) * e + a * (1 - e)
+ *    = a0 * e^2 + a * (1 - e) * (1 + e)
+ *
+ * a3 = a2 * e + a * (1 - e)
+ *    = (a0 * e^2 + a * (1 - e) * (1 + e)) * e + a * (1 - e)
+ *    = a0 * e^3 + a * (1 - e) * (1 + e + e^2)
+ *
+ *  ...
+ *
+ * an = a0 * e^n + a * (1 - e) * (1 + e + ... + e^n-1) [1]
+ *    = a0 * e^n + a * (1 - e) * (1 - e^n)/(1 - e)
+ *    = a0 * e^n + a * (1 - e^n)
+ *
+ * [1] application of the geometric series:
+ *
+ *              n         1 - x^(n+1)
+ *     S_n := \Sum x^i = -------------
+ *             i=0          1 - x
+ */
+unsigned long
+calc_load_n(unsigned long load, unsigned long exp,
+	    unsigned long active, unsigned int n)
+{
+	return calc_load(load, fixed_power_int(exp, FSHIFT, n), active);
 }
 
 #ifdef CONFIG_NO_HZ_COMMON
@@ -225,75 +279,6 @@ static long calc_load_nohz_fold(void)
 	return delta;
 }
 
-/**
- * fixed_power_int - compute: x^n, in O(log n) time
- *
- * @x:         base of the power
- * @frac_bits: fractional bits of @x
- * @n:         power to raise @x to.
- *
- * By exploiting the relation between the definition of the natural power
- * function: x^n := x*x*...*x (x multiplied by itself for n times), and
- * the binary encoding of numbers used by computers: n := \Sum n_i * 2^i,
- * (where: n_i \elem {0, 1}, the binary vector representing n),
- * we find: x^n := x^(\Sum n_i * 2^i) := \Prod x^(n_i * 2^i), which is
- * of course trivially computable in O(log_2 n), the length of our binary
- * vector.
- */
-static unsigned long
-fixed_power_int(unsigned long x, unsigned int frac_bits, unsigned int n)
-{
-	unsigned long result = 1UL << frac_bits;
-
-	if (n) {
-		for (;;) {
-			if (n & 1) {
-				result *= x;
-				result += 1UL << (frac_bits - 1);
-				result >>= frac_bits;
-			}
-			n >>= 1;
-			if (!n)
-				break;
-			x *= x;
-			x += 1UL << (frac_bits - 1);
-			x >>= frac_bits;
-		}
-	}
-
-	return result;
-}
-
-/*
- * a1 = a0 * e + a * (1 - e)
- *
- * a2 = a1 * e + a * (1 - e)
- *    = (a0 * e + a * (1 - e)) * e + a * (1 - e)
- *    = a0 * e^2 + a * (1 - e) * (1 + e)
- *
- * a3 = a2 * e + a * (1 - e)
- *    = (a0 * e^2 + a * (1 - e) * (1 + e)) * e + a * (1 - e)
- *    = a0 * e^3 + a * (1 - e) * (1 + e + e^2)
- *
- *  ...
- *
- * an = a0 * e^n + a * (1 - e) * (1 + e + ... + e^n-1) [1]
- *    = a0 * e^n + a * (1 - e) * (1 - e^n)/(1 - e)
- *    = a0 * e^n + a * (1 - e^n)
- *
- * [1] application of the geometric series:
- *
- *              n         1 - x^(n+1)
- *     S_n := \Sum x^i = -------------
- *             i=0          1 - x
- */
-static unsigned long
-calc_load_n(unsigned long load, unsigned long exp,
-	    unsigned long active, unsigned int n)
-{
-	return calc_load(load, fixed_power_int(exp, FSHIFT, n), active);
-}
-
 /*
  * NO_HZ can leave us missing all per-CPU ticks calling
  * calc_load_fold_active(), but since a NO_HZ CPU folds its delta into
diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
new file mode 100644
index 000000000000..7cdecfc010af
--- /dev/null
+++ b/kernel/sched/psi.c
@@ -0,0 +1,759 @@
+/*
+ * Pressure stall information for CPU, memory and IO
+ *
+ * Copyright (c) 2018 Facebook, Inc.
+ * Author: Johannes Weiner <hannes@cmpxchg.org>
+ *
+ * When CPU, memory and IO are contended, tasks experience delays that
+ * reduce throughput and introduce latencies into the workload. Memory
+ * and IO contention, in addition, can cause a full loss of forward
+ * progress in which the CPU goes idle.
+ *
+ * This code aggregates individual task delays into resource pressure
+ * metrics that indicate problems with both workload health and
+ * resource utilization.
+ *
+ *			Model
+ *
+ * The time in which a task can execute on a CPU is our baseline for
+ * productivity. Pressure expresses the amount of time in which this
+ * potential cannot be realized due to resource contention.
+ *
+ * This concept of productivity has two components: the workload and
+ * the CPU. To measure the impact of pressure on both, we define two
+ * contention states for a resource: SOME and FULL.
+ *
+ * In the SOME state of a given resource, one or more tasks are
+ * delayed on that resource. This affects the workload's ability to
+ * perform work, but the CPU may still be executing other tasks.
+ *
+ * In the FULL state of a given resource, all non-idle tasks are
+ * delayed on that resource such that nobody is advancing and the CPU
+ * goes idle. This leaves both workload and CPU unproductive.
+ *
+ * (Naturally, the FULL state doesn't exist for the CPU resource.)
+ *
+ *	SOME = nr_delayed_tasks != 0
+ *	FULL = nr_delayed_tasks != 0 && nr_running_tasks == 0
+ *
+ * The percentage of wallclock time spent in those compound stall
+ * states gives pressure numbers between 0 and 100 for each resource,
+ * where the SOME percentage indicates workload slowdowns and the FULL
+ * percentage indicates reduced CPU utilization:
+ *
+ *	%SOME = time(SOME) / period
+ *	%FULL = time(FULL) / period
+ *
+ *			Multiple CPUs
+ *
+ * The more tasks and available CPUs there are, the more work can be
+ * performed concurrently. This means that the potential that can go
+ * unrealized due to resource contention *also* scales with non-idle
+ * tasks and CPUs.
+ *
+ * Consider a scenario where 257 number crunching tasks are trying to
+ * run concurrently on 256 CPUs. If we simply aggregated the task
+ * states, we would have to conclude a CPU SOME pressure number of
+ * 100%, since *somebody* is waiting on a runqueue at all
+ * times. However, that is clearly not the amount of contention the
+ * workload is experiencing: only one out of 256 possible exceution
+ * threads will be contended at any given time, or about 0.4%.
+ *
+ * Conversely, consider a scenario of 4 tasks and 4 CPUs where at any
+ * given time *one* of the tasks is delayed due to a lack of memory.
+ * Again, looking purely at the task state would yield a memory FULL
+ * pressure number of 0%, since *somebody* is always making forward
+ * progress. But again this wouldn't capture the amount of execution
+ * potential lost, which is 1 out of 4 CPUs, or 25%.
+ *
+ * To calculate wasted potential (pressure) with multiple processors,
+ * we have to base our calculation on the number of non-idle tasks in
+ * conjunction with the number of available CPUs, which is the number
+ * of potential execution threads. SOME becomes then the proportion of
+ * delayed tasks to possibe threads, and FULL is the share of possible
+ * threads that are unproductive due to delays:
+ *
+ *	threads = min(nr_nonidle_tasks, nr_cpus)
+ *	   SOME = min(nr_delayed_tasks / threads, 1)
+ *	   FULL = (threads - min(nr_running_tasks, threads)) / threads
+ *
+ * For the 257 number crunchers on 256 CPUs, this yields:
+ *
+ *	threads = min(257, 256)
+ *	   SOME = min(1 / 256, 1)             = 0.4%
+ *	   FULL = (256 - min(257, 256)) / 256 = 0%
+ *
+ * For the 1 out of 4 memory-delayed tasks, this yields:
+ *
+ *	threads = min(4, 4)
+ *	   SOME = min(1 / 4, 1)               = 25%
+ *	   FULL = (4 - min(3, 4)) / 4         = 25%
+ *
+ * [ Substitute nr_cpus with 1, and you can see that it's a natural
+ *   extension of the single-CPU model. ]
+ *
+ *			Implementation
+ *
+ * To assess the precise time spent in each such state, we would have
+ * to freeze the system on task changes and start/stop the state
+ * clocks accordingly. Obviously that doesn't scale in practice.
+ *
+ * Because the scheduler aims to distribute the compute load evenly
+ * among the available CPUs, we can track task state locally to each
+ * CPU and, at much lower frequency, extrapolate the global state for
+ * the cumulative stall times and the running averages.
+ *
+ * For each runqueue, we track:
+ *
+ *	   tSOME[cpu] = time(nr_delayed_tasks[cpu] != 0)
+ *	   tFULL[cpu] = time(nr_delayed_tasks[cpu] && !nr_running_tasks[cpu])
+ *	tNONIDLE[cpu] = time(nr_nonidle_tasks[cpu] != 0)
+ *
+ * and then periodically aggregate:
+ *
+ *	tNONIDLE = sum(tNONIDLE[i])
+ *
+ *	   tSOME = sum(tSOME[i] * tNONIDLE[i]) / tNONIDLE
+ *	   tFULL = sum(tFULL[i] * tNONIDLE[i]) / tNONIDLE
+ *
+ *	   %SOME = tSOME / period
+ *	   %FULL = tFULL / period
+ *
+ * This gives us an approximation of pressure that is practical
+ * cost-wise, yet way more sensitive and accurate than periodic
+ * sampling of the aggregate task states would be.
+ */
+
+#include <linux/sched/loadavg.h>
+#include <linux/seq_file.h>
+#include <linux/proc_fs.h>
+#include <linux/seqlock.h>
+#include <linux/cgroup.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/psi.h>
+#include "sched.h"
+
+static int psi_bug __read_mostly;
+
+bool psi_disabled __read_mostly;
+core_param(psi_disabled, psi_disabled, bool, 0644);
+
+/* Running averages - we need to be higher-res than loadavg */
+#define PSI_FREQ	(2*HZ+1)	/* 2 sec intervals */
+#define EXP_10s		1677		/* 1/exp(2s/10s) as fixed-point */
+#define EXP_60s		1981		/* 1/exp(2s/60s) */
+#define EXP_300s	2034		/* 1/exp(2s/300s) */
+
+/* Sampling frequency in nanoseconds */
+static u64 psi_period __read_mostly;
+
+/* System-level pressure and stall tracking */
+static DEFINE_PER_CPU(struct psi_group_cpu, system_group_pcpu);
+static struct psi_group psi_system = {
+	.pcpu = &system_group_pcpu,
+};
+
+static void psi_update_work(struct work_struct *work);
+
+static void group_init(struct psi_group *group)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu)
+		seqcount_init(&per_cpu_ptr(group->pcpu, cpu)->seq);
+	group->next_update = sched_clock() + psi_period;
+	INIT_DELAYED_WORK(&group->clock_work, psi_update_work);
+	mutex_init(&group->stat_lock);
+}
+
+void __init psi_init(void)
+{
+	if (psi_disabled)
+		return;
+
+	psi_period = jiffies_to_nsecs(PSI_FREQ);
+	group_init(&psi_system);
+}
+
+static bool test_state(unsigned int *tasks, enum psi_states state)
+{
+	switch (state) {
+	case PSI_IO_SOME:
+		return tasks[NR_IOWAIT];
+	case PSI_IO_FULL:
+		return tasks[NR_IOWAIT] && !tasks[NR_RUNNING];
+	case PSI_MEM_SOME:
+		return tasks[NR_MEMSTALL];
+	case PSI_MEM_FULL:
+		return tasks[NR_MEMSTALL] && !tasks[NR_RUNNING];
+	case PSI_CPU_SOME:
+		return tasks[NR_RUNNING] > 1;
+	case PSI_NONIDLE:
+		return tasks[NR_IOWAIT] || tasks[NR_MEMSTALL] ||
+			tasks[NR_RUNNING];
+	default:
+		return false;
+	}
+}
+
+static void get_recent_times(struct psi_group *group, int cpu, u32 *times)
+{
+	struct psi_group_cpu *groupc = per_cpu_ptr(group->pcpu, cpu);
+	unsigned int tasks[NR_PSI_TASK_COUNTS];
+	u64 now, state_start;
+	unsigned int seq;
+	int s;
+
+	/* Snapshot a coherent view of the CPU state */
+	do {
+		seq = read_seqcount_begin(&groupc->seq);
+		now = cpu_clock(cpu);
+		memcpy(times, groupc->times, sizeof(groupc->times));
+		memcpy(tasks, groupc->tasks, sizeof(groupc->tasks));
+		state_start = groupc->state_start;
+	} while (read_seqcount_retry(&groupc->seq, seq));
+
+	/* Calculate state time deltas against the previous snapshot */
+	for (s = 0; s < NR_PSI_STATES; s++) {
+		u32 delta;
+		/*
+		 * In addition to already concluded states, we also
+		 * incorporate currently active states on the CPU,
+		 * since states may last for many sampling periods.
+		 *
+		 * This way we keep our delta sampling buckets small
+		 * (u32) and our reported pressure close to what's
+		 * actually happening.
+		 */
+		if (test_state(tasks, s))
+			times[s] += now - state_start;
+
+		delta = times[s] - groupc->times_prev[s];
+		groupc->times_prev[s] = times[s];
+
+		times[s] = delta;
+	}
+}
+
+static void calc_avgs(unsigned long avg[3], int missed_periods,
+		      u64 time, u64 period)
+{
+	unsigned long pct;
+
+	/* Fill in zeroes for periods of no activity */
+	if (missed_periods) {
+		avg[0] = calc_load_n(avg[0], EXP_10s, 0, missed_periods);
+		avg[1] = calc_load_n(avg[1], EXP_60s, 0, missed_periods);
+		avg[2] = calc_load_n(avg[2], EXP_300s, 0, missed_periods);
+	}
+
+	/* Sample the most recent active period */
+	pct = div_u64(time * 100, period);
+	pct *= FIXED_1;
+	avg[0] = calc_load(avg[0], EXP_10s, pct);
+	avg[1] = calc_load(avg[1], EXP_60s, pct);
+	avg[2] = calc_load(avg[2], EXP_300s, pct);
+}
+
+static bool update_stats(struct psi_group *group)
+{
+	u64 deltas[NR_PSI_STATES - 1] = { 0, };
+	unsigned long missed_periods = 0;
+	unsigned long nonidle_total = 0;
+	u64 now, expires, period;
+	int cpu;
+	int s;
+
+	mutex_lock(&group->stat_lock);
+
+	/*
+	 * Collect the per-cpu time buckets and average them into a
+	 * single time sample that is normalized to wallclock time.
+	 *
+	 * For averaging, each CPU is weighted by its non-idle time in
+	 * the sampling period. This eliminates artifacts from uneven
+	 * loading, or even entirely idle CPUs.
+	 */
+	for_each_possible_cpu(cpu) {
+		u32 times[NR_PSI_STATES];
+		u32 nonidle;
+
+		get_recent_times(group, cpu, times);
+
+		nonidle = nsecs_to_jiffies(times[PSI_NONIDLE]);
+		nonidle_total += nonidle;
+
+		for (s = 0; s < PSI_NONIDLE; s++)
+			deltas[s] += (u64)times[s] * nonidle;
+	}
+
+	/*
+	 * Integrate the sample into the running statistics that are
+	 * reported to userspace: the cumulative stall times and the
+	 * decaying averages.
+	 *
+	 * Pressure percentages are sampled at PSI_FREQ. We might be
+	 * called more often when the user polls more frequently than
+	 * that; we might be called less often when there is no task
+	 * activity, thus no data, and clock ticks are sporadic. The
+	 * below handles both.
+	 */
+
+	/* total= */
+	for (s = 0; s < NR_PSI_STATES - 1; s++)
+		group->total[s] += div_u64(deltas[s], max(nonidle_total, 1UL));
+
+	/* avgX= */
+	now = sched_clock();
+	expires = group->next_update;
+	if (now < expires)
+		goto out;
+	if (now - expires > psi_period)
+		missed_periods = div_u64(now - expires, psi_period);
+
+	/*
+	 * The periodic clock tick can get delayed for various
+	 * reasons, especially on loaded systems. To avoid clock
+	 * drift, we schedule the clock in fixed psi_period intervals.
+	 * But the deltas we sample out of the per-cpu buckets above
+	 * are based on the actual time elapsing between clock ticks.
+	 */
+	group->next_update = expires + ((1 + missed_periods) * psi_period);
+	period = now - (group->last_update + (missed_periods * psi_period));
+	group->last_update = now;
+
+	for (s = 0; s < NR_PSI_STATES - 1; s++) {
+		u32 sample;
+
+		sample = group->total[s] - group->total_prev[s];
+		/*
+		 * Due to the lockless sampling of the time buckets,
+		 * recorded time deltas can slip into the next period,
+		 * which under full pressure can result in samples in
+		 * excess of the period length.
+		 *
+		 * We don't want to report non-sensical pressures in
+		 * excess of 100%, nor do we want to drop such events
+		 * on the floor. Instead we punt any overage into the
+		 * future until pressure subsides. By doing this we
+		 * don't underreport the occurring pressure curve, we
+		 * just report it delayed by one period length.
+		 *
+		 * The error isn't cumulative. As soon as another
+		 * delta slips from a period P to P+1, by definition
+		 * it frees up its time T in P.
+		 */
+		if (sample > period)
+			sample = period;
+		group->total_prev[s] += sample;
+		calc_avgs(group->avg[s], missed_periods, sample, period);
+	}
+out:
+	mutex_unlock(&group->stat_lock);
+	return nonidle_total;
+}
+
+static void psi_update_work(struct work_struct *work)
+{
+	struct delayed_work *dwork;
+	struct psi_group *group;
+	bool nonidle;
+
+	dwork = to_delayed_work(work);
+	group = container_of(dwork, struct psi_group, clock_work);
+
+	/*
+	 * If there is task activity, periodically fold the per-cpu
+	 * times and feed samples into the running averages. If things
+	 * are idle and there is no data to process, stop the clock.
+	 * Once restarted, we'll catch up the running averages in one
+	 * go - see calc_avgs() and missed_periods.
+	 */
+
+	nonidle = update_stats(group);
+
+	if (nonidle) {
+		unsigned long delay = 0;
+		u64 now;
+
+		now = sched_clock();
+		if (group->next_update > now)
+			delay = nsecs_to_jiffies(group->next_update - now) + 1;
+		schedule_delayed_work(dwork, delay);
+	}
+}
+
+static void record_times(struct psi_group_cpu *groupc, int cpu,
+			 bool memstall_tick)
+{
+	u32 delta;
+	u64 now;
+
+	now = cpu_clock(cpu);
+	delta = now - groupc->state_start;
+	groupc->state_start = now;
+
+	if (test_state(groupc->tasks, PSI_IO_SOME)) {
+		groupc->times[PSI_IO_SOME] += delta;
+		if (test_state(groupc->tasks, PSI_IO_FULL))
+			groupc->times[PSI_IO_FULL] += delta;
+	}
+
+	if (test_state(groupc->tasks, PSI_MEM_SOME)) {
+		groupc->times[PSI_MEM_SOME] += delta;
+		if (test_state(groupc->tasks, PSI_MEM_FULL))
+			groupc->times[PSI_MEM_FULL] += delta;
+		else if (memstall_tick) {
+			u32 sample;
+			/*
+			 * Since we care about lost potential, a
+			 * memstall is FULL when there are no other
+			 * working tasks, but also when the CPU is
+			 * actively reclaiming and nothing productive
+			 * could run even if it were runnable.
+			 *
+			 * When the timer tick sees a reclaiming CPU,
+			 * regardless of runnable tasks, sample a FULL
+			 * tick (or less if it hasn't been a full tick
+			 * since the last state change).
+			 */
+			sample = min(delta, (u32)jiffies_to_nsecs(1));
+			groupc->times[PSI_MEM_FULL] += sample;
+		}
+	}
+
+	if (test_state(groupc->tasks, PSI_CPU_SOME))
+		groupc->times[PSI_CPU_SOME] += delta;
+
+	if (test_state(groupc->tasks, PSI_NONIDLE))
+		groupc->times[PSI_NONIDLE] += delta;
+}
+
+static void psi_group_change(struct psi_group *group, int cpu,
+			     unsigned int clear, unsigned int set)
+{
+	struct psi_group_cpu *groupc;
+	unsigned int t, m;
+
+	groupc = per_cpu_ptr(group->pcpu, cpu);
+
+	/*
+	 * First we assess the aggregate resource states this CPU's
+	 * tasks have been in since the last change, and account any
+	 * SOME and FULL time these may have resulted in.
+	 *
+	 * Then we update the task counts according to the state
+	 * change requested through the @clear and @set bits.
+	 */
+	write_seqcount_begin(&groupc->seq);
+
+	record_times(groupc, cpu, false);
+
+	for (t = 0, m = clear; m; m &= ~(1 << t), t++) {
+		if (!(m & (1 << t)))
+			continue;
+		if (groupc->tasks[t] == 0 && !psi_bug) {
+			printk_deferred(KERN_ERR "psi: task underflow! cpu=%d t=%d tasks=[%u %u %u] clear=%x set=%x\n",
+					cpu, t, groupc->tasks[0],
+					groupc->tasks[1], groupc->tasks[2],
+					clear, set);
+			psi_bug = 1;
+		}
+		groupc->tasks[t]--;
+	}
+
+	for (t = 0; set; set &= ~(1 << t), t++)
+		if (set & (1 << t))
+			groupc->tasks[t]++;
+
+	write_seqcount_end(&groupc->seq);
+
+	if (!delayed_work_pending(&group->clock_work))
+		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;
+
+	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;
+
+	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 *group;
+	void *iter = NULL;
+
+	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);
+	}
+}
+
+/**
+ * psi_memstall_enter - mark the beginning of a memory stall section
+ * @flags: flags to handle nested sections
+ *
+ * Marks the calling task as being stalled due to a lack of memory,
+ * such as waiting for a refault or performing reclaim.
+ */
+void psi_memstall_enter(unsigned long *flags)
+{
+	struct rq_flags rf;
+	struct rq *rq;
+
+	if (psi_disabled)
+		return;
+
+	*flags = current->flags & PF_MEMSTALL;
+	if (*flags)
+		return;
+	/*
+	 * PF_MEMSTALL setting & accounting needs to be atomic wrt
+	 * changes to the task's scheduling state, otherwise we can
+	 * race with CPU migration.
+	 */
+	rq = this_rq_lock_irq(&rf);
+
+	current->flags |= PF_MEMSTALL;
+	psi_task_change(current, 0, TSK_MEMSTALL);
+
+	rq_unlock_irq(rq, &rf);
+}
+
+/**
+ * psi_memstall_leave - mark the end of an memory stall section
+ * @flags: flags to handle nested memdelay sections
+ *
+ * Marks the calling task as no longer stalled due to lack of memory.
+ */
+void psi_memstall_leave(unsigned long *flags)
+{
+	struct rq_flags rf;
+	struct rq *rq;
+
+	if (psi_disabled)
+		return;
+
+	if (*flags)
+		return;
+	/*
+	 * PF_MEMSTALL clearing & accounting needs to be atomic wrt
+	 * changes to the task's scheduling state, otherwise we could
+	 * race with CPU migration.
+	 */
+	rq = this_rq_lock_irq(&rf);
+
+	current->flags &= ~PF_MEMSTALL;
+	psi_task_change(current, TSK_MEMSTALL, 0);
+
+	rq_unlock_irq(rq, &rf);
+}
+
+#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;
+
+	if (psi_disabled)
+		return -EOPNOTSUPP;
+
+	update_stats(group);
+
+	for (full = 0; full < 2 - (res == PSI_CPU); full++) {
+		unsigned long avg[3];
+		u64 total;
+		int w;
+
+		for (w = 0; w < 3; w++)
+			avg[w] = group->avg[res * 2 + full][w];
+		total = div_u64(group->total[res * 2 + full], NSEC_PER_USEC);
+
+		seq_printf(m, "%s avg10=%lu.%02lu avg60=%lu.%02lu avg300=%lu.%02lu total=%llu\n",
+			   full ? "full" : "some",
+			   LOAD_INT(avg[0]), LOAD_FRAC(avg[0]),
+			   LOAD_INT(avg[1]), LOAD_FRAC(avg[1]),
+			   LOAD_INT(avg[2]), LOAD_FRAC(avg[2]),
+			   total);
+	}
+
+	return 0;
+}
+
+static int psi_io_show(struct seq_file *m, void *v)
+{
+	return psi_show(m, &psi_system, PSI_IO);
+}
+
+static int psi_memory_show(struct seq_file *m, void *v)
+{
+	return psi_show(m, &psi_system, PSI_MEM);
+}
+
+static int psi_cpu_show(struct seq_file *m, void *v)
+{
+	return psi_show(m, &psi_system, PSI_CPU);
+}
+
+static int psi_io_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, psi_io_show, NULL);
+}
+
+static int psi_memory_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, psi_memory_show, NULL);
+}
+
+static int psi_cpu_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, psi_cpu_show, NULL);
+}
+
+static const struct file_operations psi_io_fops = {
+	.open           = psi_io_open,
+	.read           = seq_read,
+	.llseek         = seq_lseek,
+	.release        = single_release,
+};
+
+static const struct file_operations psi_memory_fops = {
+	.open           = psi_memory_open,
+	.read           = seq_read,
+	.llseek         = seq_lseek,
+	.release        = single_release,
+};
+
+static const struct file_operations psi_cpu_fops = {
+	.open           = psi_cpu_open,
+	.read           = seq_read,
+	.llseek         = seq_lseek,
+	.release        = single_release,
+};
+
+static int __init psi_proc_init(void)
+{
+	proc_mkdir("pressure", NULL);
+	proc_create("pressure/io", 0, NULL, &psi_io_fops);
+	proc_create("pressure/memory", 0, NULL, &psi_memory_fops);
+	proc_create("pressure/cpu", 0, NULL, &psi_cpu_fops);
+	return 0;
+}
+module_init(psi_proc_init);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index b8c007713b3b..618577fc9aa8 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -54,6 +54,7 @@
 #include <linux/proc_fs.h>
 #include <linux/prefetch.h>
 #include <linux/profile.h>
+#include <linux/psi.h>
 #include <linux/rcupdate_wait.h>
 #include <linux/security.h>
 #include <linux/stop_machine.h>
@@ -319,6 +320,7 @@ extern bool dl_cpu_busy(unsigned int cpu);
 #ifdef CONFIG_CGROUP_SCHED
 
 #include <linux/cgroup.h>
+#include <linux/psi.h>
 
 struct cfs_rq;
 struct rt_rq;
@@ -957,6 +959,8 @@ DECLARE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
 #define cpu_curr(cpu)		(cpu_rq(cpu)->curr)
 #define raw_rq()		raw_cpu_ptr(&runqueues)
 
+extern void update_rq_clock(struct rq *rq);
+
 static inline u64 __rq_clock_broken(struct rq *rq)
 {
 	return READ_ONCE(rq->clock);
@@ -1075,6 +1079,98 @@ static inline void rq_repin_lock(struct rq *rq, struct rq_flags *rf)
 #endif
 }
 
+struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf)
+	__acquires(rq->lock);
+
+struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf)
+	__acquires(p->pi_lock)
+	__acquires(rq->lock);
+
+static inline void __task_rq_unlock(struct rq *rq, struct rq_flags *rf)
+	__releases(rq->lock)
+{
+	rq_unpin_lock(rq, rf);
+	raw_spin_unlock(&rq->lock);
+}
+
+static inline void
+task_rq_unlock(struct rq *rq, struct task_struct *p, struct rq_flags *rf)
+	__releases(rq->lock)
+	__releases(p->pi_lock)
+{
+	rq_unpin_lock(rq, rf);
+	raw_spin_unlock(&rq->lock);
+	raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags);
+}
+
+static inline void
+rq_lock_irqsave(struct rq *rq, struct rq_flags *rf)
+	__acquires(rq->lock)
+{
+	raw_spin_lock_irqsave(&rq->lock, rf->flags);
+	rq_pin_lock(rq, rf);
+}
+
+static inline void
+rq_lock_irq(struct rq *rq, struct rq_flags *rf)
+	__acquires(rq->lock)
+{
+	raw_spin_lock_irq(&rq->lock);
+	rq_pin_lock(rq, rf);
+}
+
+static inline void
+rq_lock(struct rq *rq, struct rq_flags *rf)
+	__acquires(rq->lock)
+{
+	raw_spin_lock(&rq->lock);
+	rq_pin_lock(rq, rf);
+}
+
+static inline void
+rq_relock(struct rq *rq, struct rq_flags *rf)
+	__acquires(rq->lock)
+{
+	raw_spin_lock(&rq->lock);
+	rq_repin_lock(rq, rf);
+}
+
+static inline void
+rq_unlock_irqrestore(struct rq *rq, struct rq_flags *rf)
+	__releases(rq->lock)
+{
+	rq_unpin_lock(rq, rf);
+	raw_spin_unlock_irqrestore(&rq->lock, rf->flags);
+}
+
+static inline void
+rq_unlock_irq(struct rq *rq, struct rq_flags *rf)
+	__releases(rq->lock)
+{
+	rq_unpin_lock(rq, rf);
+	raw_spin_unlock_irq(&rq->lock);
+}
+
+static inline void
+rq_unlock(struct rq *rq, struct rq_flags *rf)
+	__releases(rq->lock)
+{
+	rq_unpin_lock(rq, rf);
+	raw_spin_unlock(&rq->lock);
+}
+
+static inline struct rq *
+this_rq_lock_irq(struct rq_flags *rf)
+	__acquires(rq->lock)
+{
+	struct rq *rq;
+
+	local_irq_disable();
+	rq = this_rq();
+	rq_lock(rq, rf);
+	return rq;
+}
+
 #ifdef CONFIG_NUMA
 enum numa_topology_type {
 	NUMA_DIRECT,
@@ -1717,8 +1813,6 @@ static inline void sub_nr_running(struct rq *rq, unsigned count)
 	sched_update_tick_dependency(rq);
 }
 
-extern void update_rq_clock(struct rq *rq);
-
 extern void activate_task(struct rq *rq, struct task_struct *p, int flags);
 extern void deactivate_task(struct rq *rq, struct task_struct *p, int flags);
 
@@ -1783,86 +1877,6 @@ unsigned long arch_scale_cpu_capacity(void __always_unused *sd, int cpu)
 #endif
 #endif
 
-struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf)
-	__acquires(rq->lock);
-
-struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf)
-	__acquires(p->pi_lock)
-	__acquires(rq->lock);
-
-static inline void __task_rq_unlock(struct rq *rq, struct rq_flags *rf)
-	__releases(rq->lock)
-{
-	rq_unpin_lock(rq, rf);
-	raw_spin_unlock(&rq->lock);
-}
-
-static inline void
-task_rq_unlock(struct rq *rq, struct task_struct *p, struct rq_flags *rf)
-	__releases(rq->lock)
-	__releases(p->pi_lock)
-{
-	rq_unpin_lock(rq, rf);
-	raw_spin_unlock(&rq->lock);
-	raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags);
-}
-
-static inline void
-rq_lock_irqsave(struct rq *rq, struct rq_flags *rf)
-	__acquires(rq->lock)
-{
-	raw_spin_lock_irqsave(&rq->lock, rf->flags);
-	rq_pin_lock(rq, rf);
-}
-
-static inline void
-rq_lock_irq(struct rq *rq, struct rq_flags *rf)
-	__acquires(rq->lock)
-{
-	raw_spin_lock_irq(&rq->lock);
-	rq_pin_lock(rq, rf);
-}
-
-static inline void
-rq_lock(struct rq *rq, struct rq_flags *rf)
-	__acquires(rq->lock)
-{
-	raw_spin_lock(&rq->lock);
-	rq_pin_lock(rq, rf);
-}
-
-static inline void
-rq_relock(struct rq *rq, struct rq_flags *rf)
-	__acquires(rq->lock)
-{
-	raw_spin_lock(&rq->lock);
-	rq_repin_lock(rq, rf);
-}
-
-static inline void
-rq_unlock_irqrestore(struct rq *rq, struct rq_flags *rf)
-	__releases(rq->lock)
-{
-	rq_unpin_lock(rq, rf);
-	raw_spin_unlock_irqrestore(&rq->lock, rf->flags);
-}
-
-static inline void
-rq_unlock_irq(struct rq *rq, struct rq_flags *rf)
-	__releases(rq->lock)
-{
-	rq_unpin_lock(rq, rf);
-	raw_spin_unlock_irq(&rq->lock);
-}
-
-static inline void
-rq_unlock(struct rq *rq, struct rq_flags *rf)
-	__releases(rq->lock)
-{
-	rq_unpin_lock(rq, rf);
-	raw_spin_unlock(&rq->lock);
-}
-
 #ifdef CONFIG_SMP
 #ifdef CONFIG_PREEMPT
 
diff --git a/kernel/sched/stats.h b/kernel/sched/stats.h
index 8aea199a39b4..4904c4677000 100644
--- a/kernel/sched/stats.h
+++ b/kernel/sched/stats.h
@@ -55,6 +55,92 @@ static inline void rq_sched_info_depart  (struct rq *rq, unsigned long long delt
 # define   schedstat_val_or_zero(var)	0
 #endif /* CONFIG_SCHEDSTATS */
 
+#ifdef CONFIG_PSI
+/*
+ * 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, 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, clear, set);
+}
+
+static inline void psi_dequeue(struct task_struct *p, 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, clear, set);
+}
+
+static inline void psi_ttwu_dequeue(struct task_struct *p)
+{
+	if (psi_disabled)
+		return;
+	/*
+	 * Is the task being migrated during a wakeup? Make sure to
+	 * deregister its sleep-persistent psi states from the old
+	 * queue, and let psi_enqueue() know it has to requeue.
+	 */
+	if (unlikely(p->in_iowait || (p->flags & PF_MEMSTALL))) {
+		struct rq_flags rf;
+		struct rq *rq;
+		int clear = 0;
+
+		if (p->in_iowait)
+			clear |= TSK_IOWAIT;
+		if (p->flags & PF_MEMSTALL)
+			clear |= TSK_MEMSTALL;
+
+		rq = __task_rq_lock(p, &rf);
+		psi_task_change(p, clear, 0);
+		p->sched_psi_wake_requeue = 1;
+		__task_rq_unlock(rq, &rf);
+	}
+}
+
+static inline void psi_task_tick(struct rq *rq)
+{
+	if (psi_disabled)
+		return;
+
+	if (unlikely(rq->curr->flags & PF_MEMSTALL))
+		psi_memstall_tick(rq->curr, cpu_of(rq));
+}
+#else /* CONFIG_PSI */
+static inline void psi_enqueue(struct task_struct *p, bool wakeup) {}
+static inline void psi_dequeue(struct task_struct *p, bool sleep) {}
+static inline void psi_ttwu_dequeue(struct task_struct *p) {}
+static inline void psi_task_tick(struct rq *rq) {}
+#endif /* CONFIG_PSI */
+
 #ifdef CONFIG_SCHED_INFO
 static inline void sched_info_reset_dequeued(struct task_struct *t)
 {