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authorNathan Zimmer <nzimmer@sgi.com>2013-02-21 15:15:08 -0800
committerIngo Molnar <mingo@kernel.org>2013-02-22 10:27:24 +0100
commitcb152ff26717961b10d0888cd983ba284cb99cd1 (patch)
treefa23de9f176321a54e60529e21389f1ac930bc30 /kernel/sched/stats.c
parent1c3e826482ab698e418c7a894440e62c76aac893 (diff)
downloadlinaro-lsk-cb152ff26717961b10d0888cd983ba284cb99cd1.tar.gz
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>
Diffstat (limited to 'kernel/sched/stats.c')
-rw-r--r--kernel/sched/stats.c79
1 files changed, 59 insertions, 20 deletions
diff --git a/kernel/sched/stats.c b/kernel/sched/stats.c
index 903ffa9e887..e036eda1a9c 100644
--- a/kernel/sched/stats.c
+++ b/kernel/sched/stats.c
@@ -21,14 +21,17 @@ static int show_schedstat(struct seq_file *seq, void *v)
if (mask_str == NULL)
return -ENOMEM;
- 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);
+ if (v == (void *)1) {
+ seq_printf(seq, "version %d\n", SCHEDSTAT_VERSION);
+ seq_printf(seq, "timestamp %lu\n", jiffies);
+ } 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)