1 files changed, 334 insertions, 0 deletions
diff --git a/kernel/cgroup/stat.c b/kernel/cgroup/stat.c
new file mode 100644
index 0000000..133b465
--- /dev/null
+++ b/kernel/cgroup/stat.c
@@ -0,0 +1,334 @@
+#include "cgroup-internal.h"
+
+#include <linux/sched/cputime.h>
+
+static DEFINE_MUTEX(cgroup_stat_mutex);
+static DEFINE_PER_CPU(raw_spinlock_t, cgroup_cpu_stat_lock);
+
+static struct cgroup_cpu_stat *cgroup_cpu_stat(struct cgroup *cgrp, int cpu)
+{
+	return per_cpu_ptr(cgrp->cpu_stat, cpu);
+}
+
+/**
+ * cgroup_cpu_stat_updated - keep track of updated cpu_stat
+ * @cgrp: target cgroup
+ * @cpu: cpu on which cpu_stat was updated
+ *
+ * @cgrp's cpu_stat on @cpu was updated.  Put it on the parent's matching
+ * cpu_stat->updated_children list.  See the comment on top of
+ * cgroup_cpu_stat definition for details.
+ */
+static void cgroup_cpu_stat_updated(struct cgroup *cgrp, int cpu)
+{
+	raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_cpu_stat_lock, cpu);
+	struct cgroup *parent;
+	unsigned long flags;
+
+	/*
+	 * Speculative already-on-list test.  This may race leading to
+	 * temporary inaccuracies, which is fine.
+	 *
+	 * Because @parent's updated_children is terminated with @parent
+	 * instead of NULL, we can tell whether @cgrp is on the list by
+	 * testing the next pointer for NULL.
+	 */
+	if (cgroup_cpu_stat(cgrp, cpu)->updated_next)
+		return;
+
+	raw_spin_lock_irqsave(cpu_lock, flags);
+
+	/* put @cgrp and all ancestors on the corresponding updated lists */
+	for (parent = cgroup_parent(cgrp); parent;
+	     cgrp = parent, parent = cgroup_parent(cgrp)) {
+		struct cgroup_cpu_stat *cstat = cgroup_cpu_stat(cgrp, cpu);
+		struct cgroup_cpu_stat *pcstat = cgroup_cpu_stat(parent, cpu);
+
+		/*
+		 * Both additions and removals are bottom-up.  If a cgroup
+		 * is already in the tree, all ancestors are.
+		 */
+		if (cstat->updated_next)
+			break;
+
+		cstat->updated_next = pcstat->updated_children;
+		pcstat->updated_children = cgrp;
+	}
+
+	raw_spin_unlock_irqrestore(cpu_lock, flags);
+}
+
+/**
+ * cgroup_cpu_stat_pop_updated - iterate and dismantle cpu_stat updated tree
+ * @pos: current position
+ * @root: root of the tree to traversal
+ * @cpu: target cpu
+ *
+ * Walks the udpated cpu_stat tree on @cpu from @root.  %NULL @pos starts
+ * the traversal and %NULL return indicates the end.  During traversal,
+ * each returned cgroup is unlinked from the tree.  Must be called with the
+ * matching cgroup_cpu_stat_lock held.
+ *
+ * The only ordering guarantee is that, for a parent and a child pair
+ * covered by a given traversal, if a child is visited, its parent is
+ * guaranteed to be visited afterwards.
+ */
+static struct cgroup *cgroup_cpu_stat_pop_updated(struct cgroup *pos,
+						  struct cgroup *root, int cpu)
+{
+	struct cgroup_cpu_stat *cstat;
+	struct cgroup *parent;
+
+	if (pos == root)
+		return NULL;
+
+	/*
+	 * We're gonna walk down to the first leaf and visit/remove it.  We
+	 * can pick whatever unvisited node as the starting point.
+	 */
+	if (!pos)
+		pos = root;
+	else
+		pos = cgroup_parent(pos);
+
+	/* walk down to the first leaf */
+	while (true) {
+		cstat = cgroup_cpu_stat(pos, cpu);
+		if (cstat->updated_children == pos)
+			break;
+		pos = cstat->updated_children;
+	}
+
+	/*
+	 * Unlink @pos from the tree.  As the updated_children list is
+	 * singly linked, we have to walk it to find the removal point.
+	 * However, due to the way we traverse, @pos will be the first
+	 * child in most cases. The only exception is @root.
+	 */
+	parent = cgroup_parent(pos);
+	if (parent && cstat->updated_next) {
+		struct cgroup_cpu_stat *pcstat = cgroup_cpu_stat(parent, cpu);
+		struct cgroup_cpu_stat *ncstat;
+		struct cgroup **nextp;
+
+		nextp = &pcstat->updated_children;
+		while (true) {
+			ncstat = cgroup_cpu_stat(*nextp, cpu);
+			if (*nextp == pos)
+				break;
+
+			WARN_ON_ONCE(*nextp == parent);
+			nextp = &ncstat->updated_next;
+		}
+
+		*nextp = cstat->updated_next;
+		cstat->updated_next = NULL;
+	}
+
+	return pos;
+}
+
+static void cgroup_stat_accumulate(struct cgroup_stat *dst_stat,
+				   struct cgroup_stat *src_stat)
+{
+	dst_stat->cputime.utime += src_stat->cputime.utime;
+	dst_stat->cputime.stime += src_stat->cputime.stime;
+	dst_stat->cputime.sum_exec_runtime += src_stat->cputime.sum_exec_runtime;
+}
+
+static void cgroup_cpu_stat_flush_one(struct cgroup *cgrp, int cpu)
+{
+	struct cgroup *parent = cgroup_parent(cgrp);
+	struct cgroup_cpu_stat *cstat = cgroup_cpu_stat(cgrp, cpu);
+	struct task_cputime *last_cputime = &cstat->last_cputime;
+	struct task_cputime cputime;
+	struct cgroup_stat delta;
+	unsigned seq;
+
+	lockdep_assert_held(&cgroup_stat_mutex);
+
+	/* fetch the current per-cpu values */
+	do {
+		seq = __u64_stats_fetch_begin(&cstat->sync);
+		cputime = cstat->cputime;
+	} while (__u64_stats_fetch_retry(&cstat->sync, seq));
+
+	/* accumulate the deltas to propgate */
+	delta.cputime.utime = cputime.utime - last_cputime->utime;
+	delta.cputime.stime = cputime.stime - last_cputime->stime;
+	delta.cputime.sum_exec_runtime = cputime.sum_exec_runtime -
+					 last_cputime->sum_exec_runtime;
+	*last_cputime = cputime;
+
+	/* transfer the pending stat into delta */
+	cgroup_stat_accumulate(&delta, &cgrp->pending_stat);
+	memset(&cgrp->pending_stat, 0, sizeof(cgrp->pending_stat));
+
+	/* propagate delta into the global stat and the parent's pending */
+	cgroup_stat_accumulate(&cgrp->stat, &delta);
+	if (parent)
+		cgroup_stat_accumulate(&parent->pending_stat, &delta);
+}
+
+/* see cgroup_stat_flush() */
+static void cgroup_stat_flush_locked(struct cgroup *cgrp)
+{
+	int cpu;
+
+	lockdep_assert_held(&cgroup_stat_mutex);
+
+	for_each_possible_cpu(cpu) {
+		raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_cpu_stat_lock, cpu);
+		struct cgroup *pos = NULL;
+
+		raw_spin_lock_irq(cpu_lock);
+		while ((pos = cgroup_cpu_stat_pop_updated(pos, cgrp, cpu)))
+			cgroup_cpu_stat_flush_one(pos, cpu);
+		raw_spin_unlock_irq(cpu_lock);
+	}
+}
+
+/**
+ * cgroup_stat_flush - flush stats in @cgrp's subtree
+ * @cgrp: target cgroup
+ *
+ * Collect all per-cpu stats in @cgrp's subtree into the global counters
+ * and propagate them upwards.  After this function returns, all cgroups in
+ * the subtree have up-to-date ->stat.
+ *
+ * This also gets all cgroups in the subtree including @cgrp off the
+ * ->updated_children lists.
+ */
+void cgroup_stat_flush(struct cgroup *cgrp)
+{
+	mutex_lock(&cgroup_stat_mutex);
+	cgroup_stat_flush_locked(cgrp);
+	mutex_unlock(&cgroup_stat_mutex);
+}
+
+static struct cgroup_cpu_stat *cgroup_cpu_stat_account_begin(struct cgroup *cgrp)
+{
+	struct cgroup_cpu_stat *cstat;
+
+	cstat = get_cpu_ptr(cgrp->cpu_stat);
+	u64_stats_update_begin(&cstat->sync);
+	return cstat;
+}
+
+static void cgroup_cpu_stat_account_end(struct cgroup *cgrp,
+					struct cgroup_cpu_stat *cstat)
+{
+	u64_stats_update_end(&cstat->sync);
+	cgroup_cpu_stat_updated(cgrp, smp_processor_id());
+	put_cpu_ptr(cstat);
+}
+
+void __cgroup_account_cputime(struct cgroup *cgrp, u64 delta_exec)
+{
+	struct cgroup_cpu_stat *cstat;
+
+	cstat = cgroup_cpu_stat_account_begin(cgrp);
+	cstat->cputime.sum_exec_runtime += delta_exec;
+	cgroup_cpu_stat_account_end(cgrp, cstat);
+}
+
+void __cgroup_account_cputime_field(struct cgroup *cgrp,
+				    enum cpu_usage_stat index, u64 delta_exec)
+{
+	struct cgroup_cpu_stat *cstat;
+
+	cstat = cgroup_cpu_stat_account_begin(cgrp);
+
+	switch (index) {
+	case CPUTIME_USER:
+	case CPUTIME_NICE:
+		cstat->cputime.utime += delta_exec;
+		break;
+	case CPUTIME_SYSTEM:
+	case CPUTIME_IRQ:
+	case CPUTIME_SOFTIRQ:
+		cstat->cputime.stime += delta_exec;
+		break;
+	default:
+		break;
+	}
+
+	cgroup_cpu_stat_account_end(cgrp, cstat);
+}
+
+void cgroup_stat_show_cputime(struct seq_file *seq)
+{
+	struct cgroup *cgrp = seq_css(seq)->cgroup;
+	u64 usage, utime, stime;
+
+	if (!cgroup_parent(cgrp))
+		return;
+
+	mutex_lock(&cgroup_stat_mutex);
+
+	cgroup_stat_flush_locked(cgrp);
+
+	usage = cgrp->stat.cputime.sum_exec_runtime;
+	cputime_adjust(&cgrp->stat.cputime, &cgrp->stat.prev_cputime,
+		       &utime, &stime);
+
+	mutex_unlock(&cgroup_stat_mutex);
+
+	do_div(usage, NSEC_PER_USEC);
+	do_div(utime, NSEC_PER_USEC);
+	do_div(stime, NSEC_PER_USEC);
+
+	seq_printf(seq, "usage_usec %llu\n"
+		   "user_usec %llu\n"
+		   "system_usec %llu\n",
+		   usage, utime, stime);
+}
+
+int cgroup_stat_init(struct cgroup *cgrp)
+{
+	int cpu;
+
+	/* the root cgrp has cpu_stat preallocated */
+	if (!cgrp->cpu_stat) {
+		cgrp->cpu_stat = alloc_percpu(struct cgroup_cpu_stat);
+		if (!cgrp->cpu_stat)
+			return -ENOMEM;
+	}
+
+	/* ->updated_children list is self terminated */
+	for_each_possible_cpu(cpu)
+		cgroup_cpu_stat(cgrp, cpu)->updated_children = cgrp;
+
+	prev_cputime_init(&cgrp->stat.prev_cputime);
+
+	return 0;
+}
+
+void cgroup_stat_exit(struct cgroup *cgrp)
+{
+	int cpu;
+
+	cgroup_stat_flush(cgrp);
+
+	/* sanity check */
+	for_each_possible_cpu(cpu) {
+		struct cgroup_cpu_stat *cstat = cgroup_cpu_stat(cgrp, cpu);
+
+		if (WARN_ON_ONCE(cstat->updated_children != cgrp) ||
+		    WARN_ON_ONCE(cstat->updated_next))
+			return;
+	}
+
+	free_percpu(cgrp->cpu_stat);
+	cgrp->cpu_stat = NULL;
+}
+
+void __init cgroup_stat_boot(void)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu)
+		raw_spin_lock_init(per_cpu_ptr(&cgroup_cpu_stat_lock, cpu));
+
+	BUG_ON(cgroup_stat_init(&cgrp_dfl_root.cgrp));
+}