sched: scheduler debugging, core

scheduler debugging core: implement /proc/sched_debug and
/proc/<PID>/sched files for scheduler debugging.

Signed-off-by: Ingo Molnar <[e-mail]>

fs/proc/base.c

···
 };
 #endif
 
+#ifdef CONFIG_SCHED_DEBUG
+/*
+ * Print out various scheduling related per-task fields:
+ */
+static int sched_show(struct seq_file *m, void *v)
+{
+	struct inode *inode = m->private;
+	struct task_struct *p;
+
+	WARN_ON(!inode);
+
+	p = get_proc_task(inode);
+	if (!p)
+		return -ESRCH;
+	proc_sched_show_task(p, m);
+
+	put_task_struct(p);
+
+	return 0;
+}
+
+static ssize_t
+sched_write(struct file *file, const char __user *buf,
+	    size_t count, loff_t *offset)
+{
+	struct inode *inode = file->f_path.dentry->d_inode;
+	struct task_struct *p;
+
+	WARN_ON(!inode);
+
+	p = get_proc_task(inode);
+	if (!p)
+		return -ESRCH;
+	proc_sched_set_task(p);
+
+	put_task_struct(p);
+
+	return count;
+}
+
+static int sched_open(struct inode *inode, struct file *filp)
+{
+	int ret;
+
+	ret = single_open(filp, sched_show, NULL);
+	if (!ret) {
+		struct seq_file *m = filp->private_data;
+
+		m->private = inode;
+	}
+	return ret;
+}
+
+static const struct file_operations proc_pid_sched_operations = {
+	.open		= sched_open,
+	.read		= seq_read,
+	.write		= sched_write,
+	.llseek		= seq_lseek,
+	.release	= seq_release,
+};
+
+#endif
+
 static void *proc_pid_follow_link(struct dentry *dentry, struct nameidata *nd)
 {
 	struct inode *inode = dentry->d_inode;
···
 	INF("environ",    S_IRUSR, pid_environ),
 	INF("auxv",       S_IRUSR, pid_auxv),
 	INF("status",     S_IRUGO, pid_status),
+#ifdef CONFIG_SCHED_DEBUG
+	REG("sched",      S_IRUGO|S_IWUSR, pid_sched),
+#endif
 	INF("cmdline",    S_IRUGO, pid_cmdline),
 	INF("stat",       S_IRUGO, tgid_stat),
 	INF("statm",      S_IRUGO, pid_statm),
···
 	INF("environ",   S_IRUSR, pid_environ),
 	INF("auxv",      S_IRUSR, pid_auxv),
 	INF("status",    S_IRUGO, pid_status),
+#ifdef CONFIG_SCHED_DEBUG
+	REG("sched",     S_IRUGO|S_IWUSR, pid_sched),
+#endif
 	INF("cmdline",   S_IRUGO, pid_cmdline),
 	INF("stat",      S_IRUGO, tid_stat),
 	INF("statm",     S_IRUGO, pid_statm),

include/linux/sched.h

···
 extern unsigned long nr_iowait(void);
 extern unsigned long weighted_cpuload(const int cpu);
 
+struct seq_file;
+struct cfs_rq;
+#ifdef CONFIG_SCHED_DEBUG
+extern void proc_sched_show_task(struct task_struct *p, struct seq_file *m);
+extern void proc_sched_set_task(struct task_struct *p);
+extern void
+print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq, u64 now);
+#else
+static inline void
+proc_sched_show_task(struct task_struct *p, struct seq_file *m)
+{
+}
+static inline void proc_sched_set_task(struct task_struct *p)
+{
+}
+static inline void
+print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq, u64 now)
+{
+}
+#endif
 
 /*
  * Task state bitmask. NOTE! These bits are also

kernel/sched_debug.c

···
+/*
+ * kernel/time/sched_debug.c
+ *
+ * Print the CFS rbtree
+ *
+ * Copyright(C) 2007, Red Hat, Inc., Ingo Molnar
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/proc_fs.h>
+#include <linux/sched.h>
+#include <linux/seq_file.h>
+#include <linux/kallsyms.h>
+#include <linux/utsname.h>
+
+/*
+ * This allows printing both to /proc/sched_debug and
+ * to the console
+ */
+#define SEQ_printf(m, x...)			\
+ do {						\
+	if (m)					\
+		seq_printf(m, x);		\
+	else					\
+		printk(x);			\
+ } while (0)
+
+static void
+print_task(struct seq_file *m, struct rq *rq, struct task_struct *p, u64 now)
+{
+	if (rq->curr == p)
+		SEQ_printf(m, "R");
+	else
+		SEQ_printf(m, " ");
+
+	SEQ_printf(m, "%15s %5d %15Ld %13Ld %13Ld %9Ld %5d "
+		      "%15Ld %15Ld %15Ld %15Ld %15Ld\n",
+		p->comm, p->pid,
+		(long long)p->se.fair_key,
+		(long long)(p->se.fair_key - rq->cfs.fair_clock),
+		(long long)p->se.wait_runtime,
+		(long long)(p->nvcsw + p->nivcsw),
+		p->prio,
+		(long long)p->se.sum_exec_runtime,
+		(long long)p->se.sum_wait_runtime,
+		(long long)p->se.sum_sleep_runtime,
+		(long long)p->se.wait_runtime_overruns,
+		(long long)p->se.wait_runtime_underruns);
+}
+
+static void print_rq(struct seq_file *m, struct rq *rq, int rq_cpu, u64 now)
+{
+	struct task_struct *g, *p;
+
+	SEQ_printf(m,
+	"\nrunnable tasks:\n"
+	"            task   PID        tree-key         delta       waiting"
+	"  switches  prio"
+	"        sum-exec        sum-wait       sum-sleep"
+	"    wait-overrun   wait-underrun\n"
+	"------------------------------------------------------------------"
+	"----------------"
+	"------------------------------------------------"
+	"--------------------------------\n");
+
+	read_lock_irq(&tasklist_lock);
+
+	do_each_thread(g, p) {
+		if (!p->se.on_rq || task_cpu(p) != rq_cpu)
+			continue;
+
+		print_task(m, rq, p, now);
+	} while_each_thread(g, p);
+
+	read_unlock_irq(&tasklist_lock);
+}
+
+static void
+print_cfs_rq_runtime_sum(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
+{
+	s64 wait_runtime_rq_sum = 0;
+	struct task_struct *p;
+	struct rb_node *curr;
+	unsigned long flags;
+	struct rq *rq = &per_cpu(runqueues, cpu);
+
+	spin_lock_irqsave(&rq->lock, flags);
+	curr = first_fair(cfs_rq);
+	while (curr) {
+		p = rb_entry(curr, struct task_struct, se.run_node);
+		wait_runtime_rq_sum += p->se.wait_runtime;
+
+		curr = rb_next(curr);
+	}
+	spin_unlock_irqrestore(&rq->lock, flags);
+
+	SEQ_printf(m, "  .%-30s: %Ld\n", "wait_runtime_rq_sum",
+		(long long)wait_runtime_rq_sum);
+}
+
+void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq, u64 now)
+{
+	SEQ_printf(m, "\ncfs_rq %p\n", cfs_rq);
+
+#define P(x) \
+	SEQ_printf(m, "  .%-30s: %Ld\n", #x, (long long)(cfs_rq->x))
+
+	P(fair_clock);
+	P(exec_clock);
+	P(wait_runtime);
+	P(wait_runtime_overruns);
+	P(wait_runtime_underruns);
+	P(sleeper_bonus);
+#undef P
+
+	print_cfs_rq_runtime_sum(m, cpu, cfs_rq);
+}
+
+static void print_cpu(struct seq_file *m, int cpu, u64 now)
+{
+	struct rq *rq = &per_cpu(runqueues, cpu);
+
+#ifdef CONFIG_X86
+	{
+		unsigned int freq = cpu_khz ? : 1;
+
+		SEQ_printf(m, "\ncpu#%d, %u.%03u MHz\n",
+			   cpu, freq / 1000, (freq % 1000));
+	}
+#else
+	SEQ_printf(m, "\ncpu#%d\n", cpu);
+#endif
+
+#define P(x) \
+	SEQ_printf(m, "  .%-30s: %Ld\n", #x, (long long)(rq->x))
+
+	P(nr_running);
+	SEQ_printf(m, "  .%-30s: %lu\n", "load",
+		   rq->ls.load.weight);
+	P(ls.delta_fair);
+	P(ls.delta_exec);
+	P(nr_switches);
+	P(nr_load_updates);
+	P(nr_uninterruptible);
+	SEQ_printf(m, "  .%-30s: %lu\n", "jiffies", jiffies);
+	P(next_balance);
+	P(curr->pid);
+	P(clock);
+	P(prev_clock_raw);
+	P(clock_warps);
+	P(clock_overflows);
+	P(clock_unstable_events);
+	P(clock_max_delta);
+	P(cpu_load[0]);
+	P(cpu_load[1]);
+	P(cpu_load[2]);
+	P(cpu_load[3]);
+	P(cpu_load[4]);
+#undef P
+
+	print_cfs_stats(m, cpu, now);
+
+	print_rq(m, rq, cpu, now);
+}
+
+static int sched_debug_show(struct seq_file *m, void *v)
+{
+	u64 now = ktime_to_ns(ktime_get());
+	int cpu;
+
+	SEQ_printf(m, "Sched Debug Version: v0.04, cfs-v20, %s %.*s\n",
+		init_utsname()->release,
+		(int)strcspn(init_utsname()->version, " "),
+		init_utsname()->version);
+
+	SEQ_printf(m, "now at %Lu nsecs\n", (unsigned long long)now);
+
+	for_each_online_cpu(cpu)
+		print_cpu(m, cpu, now);
+
+	SEQ_printf(m, "\n");
+
+	return 0;
+}
+
+void sysrq_sched_debug_show(void)
+{
+	sched_debug_show(NULL, NULL);
+}
+
+static int sched_debug_open(struct inode *inode, struct file *filp)
+{
+	return single_open(filp, sched_debug_show, NULL);
+}
+
+static struct file_operations sched_debug_fops = {
+	.open		= sched_debug_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= seq_release,
+};
+
+static int __init init_sched_debug_procfs(void)
+{
+	struct proc_dir_entry *pe;
+
+	pe = create_proc_entry("sched_debug", 0644, NULL);
+	if (!pe)
+		return -ENOMEM;
+
+	pe->proc_fops = &sched_debug_fops;
+
+	return 0;
+}
+
+__initcall(init_sched_debug_procfs);
+
+void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
+{
+	unsigned long flags;
+	int num_threads = 1;
+
+	rcu_read_lock();
+	if (lock_task_sighand(p, &flags)) {
+		num_threads = atomic_read(&p->signal->count);
+		unlock_task_sighand(p, &flags);
+	}
+	rcu_read_unlock();
+
+	SEQ_printf(m, "%s (%d, #threads: %d)\n", p->comm, p->pid, num_threads);
+	SEQ_printf(m, "----------------------------------------------\n");
+#define P(F) \
+	SEQ_printf(m, "%-25s:%20Ld\n", #F, (long long)p->F)
+
+	P(se.wait_start);
+	P(se.wait_start_fair);
+	P(se.exec_start);
+	P(se.sleep_start);
+	P(se.sleep_start_fair);
+	P(se.block_start);
+	P(se.sleep_max);
+	P(se.block_max);
+	P(se.exec_max);
+	P(se.wait_max);
+	P(se.wait_runtime);
+	P(se.wait_runtime_overruns);
+	P(se.wait_runtime_underruns);
+	P(se.sum_wait_runtime);
+	P(se.sum_exec_runtime);
+	SEQ_printf(m, "%-25s:%20Ld\n",
+		   "nr_switches", (long long)(p->nvcsw + p->nivcsw));
+	P(se.load.weight);
+	P(policy);
+	P(prio);
+#undef P
+
+	{
+		u64 t0, t1;
+
+		t0 = sched_clock();
+		t1 = sched_clock();
+		SEQ_printf(m, "%-25s:%20Ld\n",
+			   "clock-delta", (long long)(t1-t0));
+	}
+}
+
+void proc_sched_set_task(struct task_struct *p)
+{
+	p->se.sleep_max = p->se.block_max = p->se.exec_max = p->se.wait_max = 0;
+	p->se.wait_runtime_overruns = p->se.wait_runtime_underruns = 0;
+	p->se.sum_exec_runtime = 0;
+}