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Commit cb152ff2 authored by Nathan Zimmer's avatar Nathan Zimmer Committed by Ingo Molnar
Browse files

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



On systems with 4096 cores doing a cat /proc/sched_stat 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 use the single_open() mechanism but
to provide our own seq_operations.

The output should be identical to previous version and thus not
need the version number.

Reported-by: default avatarDave Jones <davej@redhat.com>
Signed-off-by: default avatarNathan Zimmer <nzimmer@sgi.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
[ Fix memleak]
[ Fix spello in comment]
[ Fix warnings]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 1c3e8264

kernel/sched/stats.c

+59 −20
Original line number Diff line number Diff line
@@ -21,14 +21,17 @@ static int show_schedstat(struct seq_file *seq, void *v) 
	if (mask_str == NULL)

		return -ENOMEM;



	if (v == (void *)1) {

		seq_printf(seq, "version %d\n", SCHEDSTAT_VERSION);

		seq_printf(seq, "timestamp %lu\n", jiffies);

	for_each_online_cpu(cpu) {

		struct rq *rq = cpu_rq(cpu);

	} else {

		struct rq *rq;

#ifdef CONFIG_SMP

		struct sched_domain *sd;

		int dcount = 0;

#endif

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

		rq = cpu_rq(cpu);



		/* runqueue-specific stats */

		seq_printf(seq,
@@ -77,30 +80,66 @@ static int show_schedstat(struct seq_file *seq, void *v) 
	return 0;

}



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

/*

 * 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 *schedstat_start(struct seq_file *file, loff_t *offset)

{

	unsigned int size = PAGE_SIZE * (1 + num_online_cpus() / 32);

	char *buf = kmalloc(size, GFP_KERNEL);

	struct seq_file *m;

	int res;

	unsigned long n = *offset;



	if (!buf)

		return -ENOMEM;

	res = single_open(file, show_schedstat, NULL);

	if (!res) {

		m = file->private_data;

		m->buf = buf;

		m->size = size;

	} else

		kfree(buf);

	return res;

	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 *schedstat_next(struct seq_file *file, void *data, loff_t *offset)

{

	(*offset)++;

	return schedstat_start(file, offset);

}



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

{

}



static const struct seq_operations schedstat_sops = {

	.start = schedstat_start,

	.next  = schedstat_next,

	.stop  = schedstat_stop,

	.show  = show_schedstat,

};



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

{

	return seq_open(file, &schedstat_sops);

}



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

{

	return 0;

};



static const struct file_operations proc_schedstat_operations = {

	.open    = schedstat_open,

	.read    = seq_read,

	.llseek  = seq_lseek,

	.release = single_release,

	.release = schedstat_release,

};



static int __init proc_schedstat_init(void)