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Commit bbbfeac9 authored by Nathan Zimmer's avatar Nathan Zimmer Committed by Ingo Molnar
Browse files

sched: Fix /proc/sched_debug failure on very very large systems 



On systems with 4096 cores attemping to read /proc/sched_debug
fails because we are trying to push all the data into a single
kmalloc buffer.

The issue is on these very large machines all the data will not
fit in 4mb.

A better solution is to not us the single_open mechanism but to
provide our own seq_operations and treat each cpu as an
individual record.

The output should be identical to the previous version.

Reported-by: default avatarDave Jones <davej@redhat.com>
Signed-off-by: default avatarNathan Zimmer <nzimmer@sgi.com>
Cc: Peter Zijlstra <peterz@infradead.org>)
[ Whitespace fixlet]
[ Fix spello in comment]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent cb152ff2

kernel/sched/debug.c

+79 −11
Original line number Diff line number Diff line
@@ -269,11 +269,11 @@ static void print_cpu(struct seq_file *m, int cpu) 
	{

		unsigned int freq = cpu_khz ? : 1;



		SEQ_printf(m, "\ncpu#%d, %u.%03u MHz\n",

		SEQ_printf(m, "cpu#%d, %u.%03u MHz\n",

			   cpu, freq / 1000, (freq % 1000));

	}

#else

	SEQ_printf(m, "\ncpu#%d\n", cpu);

	SEQ_printf(m, "cpu#%d\n", cpu);

#endif



#define P(x)								\
@@ -330,6 +330,7 @@ do { \ 
	print_rq(m, rq, cpu);

	rcu_read_unlock();

	spin_unlock_irqrestore(&sched_debug_lock, flags);

	SEQ_printf(m, "\n");

}



static const char *sched_tunable_scaling_names[] = {
@@ -338,11 +339,10 @@ static const char *sched_tunable_scaling_names[] = { 
	"linear"

};



static int sched_debug_show(struct seq_file *m, void *v)

static void sched_debug_header(struct seq_file *m)

{

	u64 ktime, sched_clk, cpu_clk;

	unsigned long flags;

	int cpu;



	local_irq_save(flags);

	ktime = ktime_to_ns(ktime_get());
@@ -384,33 +384,101 @@ static int sched_debug_show(struct seq_file *m, void *v) 
#undef PN

#undef P



	SEQ_printf(m, "  .%-40s: %d (%s)\n", "sysctl_sched_tunable_scaling",

	SEQ_printf(m, "  .%-40s: %d (%s)\n",

		"sysctl_sched_tunable_scaling",

		sysctl_sched_tunable_scaling,

		sched_tunable_scaling_names[sysctl_sched_tunable_scaling]);

	SEQ_printf(m, "\n");

}



	for_each_online_cpu(cpu)

		print_cpu(m, cpu);

static int sched_debug_show(struct seq_file *m, void *v)

{

	int cpu = (unsigned long)(v - 2);



	SEQ_printf(m, "\n");

	if (cpu != -1)

		print_cpu(m, cpu);

	else

		sched_debug_header(m);



	return 0;

}



void sysrq_sched_debug_show(void)

{

	sched_debug_show(NULL, NULL);

	int cpu;



	sched_debug_header(NULL);

	for_each_online_cpu(cpu)

		print_cpu(NULL, cpu);



}



/*

 * This itererator needs some explanation.

 * It returns 1 for the header position.

 * This means 2 is cpu 0.

 * In a hotplugged system some cpus, including cpu 0, may be missing so we have

 * to use cpumask_* to iterate over the cpus.

 */

static void *sched_debug_start(struct seq_file *file, loff_t *offset)

{

	unsigned long n = *offset;



	if (n == 0)

		return (void *) 1;



	n--;



	if (n > 0)

		n = cpumask_next(n - 1, cpu_online_mask);

	else

		n = cpumask_first(cpu_online_mask);



	*offset = n + 1;



	if (n < nr_cpu_ids)

		return (void *)(unsigned long)(n + 2);

	return NULL;

}



static void *sched_debug_next(struct seq_file *file, void *data, loff_t *offset)

{

	(*offset)++;

	return sched_debug_start(file, offset);

}



static void sched_debug_stop(struct seq_file *file, void *data)

{

}



static const struct seq_operations sched_debug_sops = {

	.start = sched_debug_start,

	.next = sched_debug_next,

	.stop = sched_debug_stop,

	.show = sched_debug_show,

};



static int sched_debug_release(struct inode *inode, struct file *file)

{

	seq_release(inode, file);



	return 0;

}



static int sched_debug_open(struct inode *inode, struct file *filp)

{

	return single_open(filp, sched_debug_show, NULL);

	int ret = 0;



	ret = seq_open(filp, &sched_debug_sops);



	return ret;

}



static const struct file_operations sched_debug_fops = {

	.open		= sched_debug_open,

	.read		= seq_read,

	.llseek		= seq_lseek,

	.release	= single_release,

	.release	= sched_debug_release,

};



static int __init init_sched_debug_procfs(void)