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a25cac5198
show_stat handler of the /proc/stat file relies on kstat_cpu(cpu)
statistics when priting information about idle and iowait times.
This is OK if we are not using tickless kernel (CONFIG_NO_HZ) because
counters are updated periodically.
With NO_HZ things got more tricky because we are not doing idle/iowait
accounting while we are tickless so the value might get outdated.
Users of /proc/stat will notice that by unchanged idle/iowait values
which is then interpreted as 0% idle/iowait time. From the user space
POV this is an unexpected behavior and a change of the interface.
Let's fix this by using get_cpu_{idle,iowait}_time_us which accounts the
total idle/iowait time since boot and it doesn't rely on sampling or any
other periodic activity. Fall back to the previous behavior if NO_HZ is
disabled or not configured.
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Cc: Dave Jones <davej@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Link: http://lkml.kernel.org/r/39181366adac1b39cb6aa3cd53ff0f7c78d32676.1314172057.git.mhocko@suse.cz
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
198 lines
5.4 KiB
C
198 lines
5.4 KiB
C
#include <linux/cpumask.h>
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#include <linux/fs.h>
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#include <linux/init.h>
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#include <linux/interrupt.h>
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#include <linux/kernel_stat.h>
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#include <linux/proc_fs.h>
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#include <linux/sched.h>
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#include <linux/seq_file.h>
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#include <linux/slab.h>
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#include <linux/time.h>
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#include <linux/irqnr.h>
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#include <asm/cputime.h>
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#include <linux/tick.h>
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#ifndef arch_irq_stat_cpu
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#define arch_irq_stat_cpu(cpu) 0
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#endif
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#ifndef arch_irq_stat
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#define arch_irq_stat() 0
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#endif
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#ifndef arch_idle_time
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#define arch_idle_time(cpu) 0
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#endif
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static cputime64_t get_idle_time(int cpu)
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{
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u64 idle_time = get_cpu_idle_time_us(cpu, NULL);
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cputime64_t idle;
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if (idle_time == -1ULL) {
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/* !NO_HZ so we can rely on cpustat.idle */
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idle = kstat_cpu(cpu).cpustat.idle;
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idle = cputime64_add(idle, arch_idle_time(cpu));
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} else
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idle = usecs_to_cputime(idle_time);
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return idle;
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}
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static cputime64_t get_iowait_time(int cpu)
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{
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u64 iowait_time = get_cpu_iowait_time_us(cpu, NULL);
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cputime64_t iowait;
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if (iowait_time == -1ULL)
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/* !NO_HZ so we can rely on cpustat.iowait */
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iowait = kstat_cpu(cpu).cpustat.iowait;
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else
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iowait = usecs_to_cputime(iowait_time);
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return iowait;
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}
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static int show_stat(struct seq_file *p, void *v)
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{
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int i, j;
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unsigned long jif;
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cputime64_t user, nice, system, idle, iowait, irq, softirq, steal;
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cputime64_t guest, guest_nice;
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u64 sum = 0;
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u64 sum_softirq = 0;
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unsigned int per_softirq_sums[NR_SOFTIRQS] = {0};
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struct timespec boottime;
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user = nice = system = idle = iowait =
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irq = softirq = steal = cputime64_zero;
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guest = guest_nice = cputime64_zero;
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getboottime(&boottime);
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jif = boottime.tv_sec;
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for_each_possible_cpu(i) {
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user = cputime64_add(user, kstat_cpu(i).cpustat.user);
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nice = cputime64_add(nice, kstat_cpu(i).cpustat.nice);
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system = cputime64_add(system, kstat_cpu(i).cpustat.system);
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idle = cputime64_add(idle, get_idle_time(i));
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iowait = cputime64_add(iowait, get_iowait_time(i));
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irq = cputime64_add(irq, kstat_cpu(i).cpustat.irq);
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softirq = cputime64_add(softirq, kstat_cpu(i).cpustat.softirq);
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steal = cputime64_add(steal, kstat_cpu(i).cpustat.steal);
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guest = cputime64_add(guest, kstat_cpu(i).cpustat.guest);
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guest_nice = cputime64_add(guest_nice,
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kstat_cpu(i).cpustat.guest_nice);
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sum += kstat_cpu_irqs_sum(i);
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sum += arch_irq_stat_cpu(i);
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for (j = 0; j < NR_SOFTIRQS; j++) {
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unsigned int softirq_stat = kstat_softirqs_cpu(j, i);
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per_softirq_sums[j] += softirq_stat;
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sum_softirq += softirq_stat;
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}
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}
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sum += arch_irq_stat();
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seq_printf(p, "cpu %llu %llu %llu %llu %llu %llu %llu %llu %llu "
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"%llu\n",
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(unsigned long long)cputime64_to_clock_t(user),
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(unsigned long long)cputime64_to_clock_t(nice),
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(unsigned long long)cputime64_to_clock_t(system),
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(unsigned long long)cputime64_to_clock_t(idle),
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(unsigned long long)cputime64_to_clock_t(iowait),
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(unsigned long long)cputime64_to_clock_t(irq),
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(unsigned long long)cputime64_to_clock_t(softirq),
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(unsigned long long)cputime64_to_clock_t(steal),
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(unsigned long long)cputime64_to_clock_t(guest),
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(unsigned long long)cputime64_to_clock_t(guest_nice));
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for_each_online_cpu(i) {
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/* Copy values here to work around gcc-2.95.3, gcc-2.96 */
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user = kstat_cpu(i).cpustat.user;
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nice = kstat_cpu(i).cpustat.nice;
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system = kstat_cpu(i).cpustat.system;
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idle = get_idle_time(i);
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iowait = get_iowait_time(i);
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irq = kstat_cpu(i).cpustat.irq;
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softirq = kstat_cpu(i).cpustat.softirq;
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steal = kstat_cpu(i).cpustat.steal;
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guest = kstat_cpu(i).cpustat.guest;
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guest_nice = kstat_cpu(i).cpustat.guest_nice;
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seq_printf(p,
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"cpu%d %llu %llu %llu %llu %llu %llu %llu %llu %llu "
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"%llu\n",
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i,
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(unsigned long long)cputime64_to_clock_t(user),
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(unsigned long long)cputime64_to_clock_t(nice),
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(unsigned long long)cputime64_to_clock_t(system),
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(unsigned long long)cputime64_to_clock_t(idle),
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(unsigned long long)cputime64_to_clock_t(iowait),
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(unsigned long long)cputime64_to_clock_t(irq),
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(unsigned long long)cputime64_to_clock_t(softirq),
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(unsigned long long)cputime64_to_clock_t(steal),
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(unsigned long long)cputime64_to_clock_t(guest),
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(unsigned long long)cputime64_to_clock_t(guest_nice));
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}
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seq_printf(p, "intr %llu", (unsigned long long)sum);
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/* sum again ? it could be updated? */
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for_each_irq_nr(j)
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seq_printf(p, " %u", kstat_irqs(j));
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seq_printf(p,
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"\nctxt %llu\n"
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"btime %lu\n"
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"processes %lu\n"
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"procs_running %lu\n"
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"procs_blocked %lu\n",
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nr_context_switches(),
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(unsigned long)jif,
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total_forks,
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nr_running(),
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nr_iowait());
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seq_printf(p, "softirq %llu", (unsigned long long)sum_softirq);
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for (i = 0; i < NR_SOFTIRQS; i++)
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seq_printf(p, " %u", per_softirq_sums[i]);
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seq_putc(p, '\n');
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return 0;
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}
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static int stat_open(struct inode *inode, struct file *file)
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{
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unsigned size = 4096 * (1 + num_possible_cpus() / 32);
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char *buf;
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struct seq_file *m;
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int res;
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/* don't ask for more than the kmalloc() max size */
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if (size > KMALLOC_MAX_SIZE)
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size = KMALLOC_MAX_SIZE;
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buf = kmalloc(size, GFP_KERNEL);
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if (!buf)
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return -ENOMEM;
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res = single_open(file, show_stat, 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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}
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static const struct file_operations proc_stat_operations = {
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.open = stat_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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};
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static int __init proc_stat_init(void)
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{
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proc_create("stat", 0, NULL, &proc_stat_operations);
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return 0;
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}
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module_init(proc_stat_init);
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