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: Dave Jones <davej@redhat.com> Signed-off-by: Nathan 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: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -21,14 +21,17 @@ static int show_schedstat(struct seq_file *seq, void *v)
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if (mask_str == NULL)
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return -ENOMEM;
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seq_printf(seq, "version %d\n", SCHEDSTAT_VERSION);
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seq_printf(seq, "timestamp %lu\n", jiffies);
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for_each_online_cpu(cpu) {
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struct rq *rq = cpu_rq(cpu);
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if (v == (void *)1) {
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seq_printf(seq, "version %d\n", SCHEDSTAT_VERSION);
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seq_printf(seq, "timestamp %lu\n", jiffies);
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} else {
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struct rq *rq;
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#ifdef CONFIG_SMP
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struct sched_domain *sd;
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int dcount = 0;
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#endif
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cpu = (unsigned long)(v - 2);
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rq = cpu_rq(cpu);
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/* runqueue-specific stats */
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seq_printf(seq,
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@ -77,30 +80,66 @@ static int show_schedstat(struct seq_file *seq, void *v)
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return 0;
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}
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/*
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* This itererator needs some explanation.
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* It returns 1 for the header position.
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* This means 2 is cpu 0.
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* In a hotplugged system some cpus, including cpu 0, may be missing so we have
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* to use cpumask_* to iterate over the cpus.
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*/
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static void *schedstat_start(struct seq_file *file, loff_t *offset)
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{
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unsigned long n = *offset;
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if (n == 0)
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return (void *) 1;
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n--;
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if (n > 0)
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n = cpumask_next(n - 1, cpu_online_mask);
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else
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n = cpumask_first(cpu_online_mask);
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*offset = n + 1;
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if (n < nr_cpu_ids)
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return (void *)(unsigned long)(n + 2);
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return NULL;
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}
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static void *schedstat_next(struct seq_file *file, void *data, loff_t *offset)
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{
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(*offset)++;
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return schedstat_start(file, offset);
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}
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static void schedstat_stop(struct seq_file *file, void *data)
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{
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}
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static const struct seq_operations schedstat_sops = {
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.start = schedstat_start,
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.next = schedstat_next,
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.stop = schedstat_stop,
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.show = show_schedstat,
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};
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static int schedstat_open(struct inode *inode, struct file *file)
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{
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unsigned int size = PAGE_SIZE * (1 + num_online_cpus() / 32);
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char *buf = kmalloc(size, GFP_KERNEL);
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struct seq_file *m;
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int res;
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if (!buf)
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return -ENOMEM;
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res = single_open(file, show_schedstat, NULL);
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if (!res) {
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m = file->private_data;
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m->buf = buf;
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m->size = size;
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} else
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kfree(buf);
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return res;
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return seq_open(file, &schedstat_sops);
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}
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static int schedstat_release(struct inode *inode, struct file *file)
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{
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return 0;
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};
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static const struct file_operations proc_schedstat_operations = {
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.open = schedstat_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = single_release,
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.release = schedstat_release,
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};
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static int __init proc_schedstat_init(void)
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