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https://github.com/torvalds/linux
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a130e8fbc7
/proc/uptime reports idle time by reading the CPUTIME_IDLE field from
the per-cpu kcpustats. However, on NO_HZ systems, idle time is not
continually updated on idle cpus, leading this value to appear
incorrectly small.
/proc/stat performs an accounting update when reading idle time; we
can use the same approach for uptime.
With this patch, /proc/stat and /proc/uptime now agree on idle time.
Additionally, the following shows idle time tick up consistently on an
idle machine:
(while true; do cat /proc/uptime; sleep 1; done) | awk '{print $2-prev; prev=$2}'
Reported-by: Luigi Rizzo <lrizzo@google.com>
Signed-off-by: Josh Don <joshdon@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lkml.kernel.org/r/20210827165438.3280779-1-joshdon@google.com
242 lines
6.2 KiB
C
242 lines
6.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#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/sched/stat.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/time_namespace.h>
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#include <linux/irqnr.h>
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#include <linux/sched/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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#ifdef arch_idle_time
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u64 get_idle_time(struct kernel_cpustat *kcs, int cpu)
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{
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u64 idle;
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idle = kcs->cpustat[CPUTIME_IDLE];
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if (cpu_online(cpu) && !nr_iowait_cpu(cpu))
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idle += arch_idle_time(cpu);
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return idle;
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}
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static u64 get_iowait_time(struct kernel_cpustat *kcs, int cpu)
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{
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u64 iowait;
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iowait = kcs->cpustat[CPUTIME_IOWAIT];
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if (cpu_online(cpu) && nr_iowait_cpu(cpu))
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iowait += arch_idle_time(cpu);
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return iowait;
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}
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#else
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u64 get_idle_time(struct kernel_cpustat *kcs, int cpu)
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{
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u64 idle, idle_usecs = -1ULL;
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if (cpu_online(cpu))
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idle_usecs = get_cpu_idle_time_us(cpu, NULL);
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if (idle_usecs == -1ULL)
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/* !NO_HZ or cpu offline so we can rely on cpustat.idle */
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idle = kcs->cpustat[CPUTIME_IDLE];
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else
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idle = idle_usecs * NSEC_PER_USEC;
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return idle;
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}
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static u64 get_iowait_time(struct kernel_cpustat *kcs, int cpu)
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{
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u64 iowait, iowait_usecs = -1ULL;
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if (cpu_online(cpu))
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iowait_usecs = get_cpu_iowait_time_us(cpu, NULL);
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if (iowait_usecs == -1ULL)
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/* !NO_HZ or cpu offline so we can rely on cpustat.iowait */
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iowait = kcs->cpustat[CPUTIME_IOWAIT];
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else
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iowait = iowait_usecs * NSEC_PER_USEC;
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return iowait;
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}
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#endif
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static void show_irq_gap(struct seq_file *p, unsigned int gap)
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{
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static const char zeros[] = " 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0";
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while (gap > 0) {
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unsigned int inc;
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inc = min_t(unsigned int, gap, ARRAY_SIZE(zeros) / 2);
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seq_write(p, zeros, 2 * inc);
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gap -= inc;
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}
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}
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static void show_all_irqs(struct seq_file *p)
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{
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unsigned int i, next = 0;
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for_each_active_irq(i) {
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show_irq_gap(p, i - next);
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seq_put_decimal_ull(p, " ", kstat_irqs_usr(i));
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next = i + 1;
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}
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show_irq_gap(p, nr_irqs - next);
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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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u64 user, nice, system, idle, iowait, irq, softirq, steal;
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u64 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 timespec64 boottime;
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user = nice = system = idle = iowait =
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irq = softirq = steal = 0;
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guest = guest_nice = 0;
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getboottime64(&boottime);
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/* shift boot timestamp according to the timens offset */
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timens_sub_boottime(&boottime);
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for_each_possible_cpu(i) {
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struct kernel_cpustat kcpustat;
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u64 *cpustat = kcpustat.cpustat;
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kcpustat_cpu_fetch(&kcpustat, i);
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user += cpustat[CPUTIME_USER];
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nice += cpustat[CPUTIME_NICE];
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system += cpustat[CPUTIME_SYSTEM];
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idle += get_idle_time(&kcpustat, i);
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iowait += get_iowait_time(&kcpustat, i);
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irq += cpustat[CPUTIME_IRQ];
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softirq += cpustat[CPUTIME_SOFTIRQ];
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steal += cpustat[CPUTIME_STEAL];
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guest += cpustat[CPUTIME_GUEST];
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guest_nice += cpustat[CPUTIME_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_put_decimal_ull(p, "cpu ", nsec_to_clock_t(user));
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seq_put_decimal_ull(p, " ", nsec_to_clock_t(nice));
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seq_put_decimal_ull(p, " ", nsec_to_clock_t(system));
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seq_put_decimal_ull(p, " ", nsec_to_clock_t(idle));
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seq_put_decimal_ull(p, " ", nsec_to_clock_t(iowait));
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seq_put_decimal_ull(p, " ", nsec_to_clock_t(irq));
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seq_put_decimal_ull(p, " ", nsec_to_clock_t(softirq));
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seq_put_decimal_ull(p, " ", nsec_to_clock_t(steal));
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seq_put_decimal_ull(p, " ", nsec_to_clock_t(guest));
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seq_put_decimal_ull(p, " ", nsec_to_clock_t(guest_nice));
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seq_putc(p, '\n');
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for_each_online_cpu(i) {
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struct kernel_cpustat kcpustat;
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u64 *cpustat = kcpustat.cpustat;
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kcpustat_cpu_fetch(&kcpustat, i);
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/* Copy values here to work around gcc-2.95.3, gcc-2.96 */
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user = cpustat[CPUTIME_USER];
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nice = cpustat[CPUTIME_NICE];
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system = cpustat[CPUTIME_SYSTEM];
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idle = get_idle_time(&kcpustat, i);
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iowait = get_iowait_time(&kcpustat, i);
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irq = cpustat[CPUTIME_IRQ];
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softirq = cpustat[CPUTIME_SOFTIRQ];
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steal = cpustat[CPUTIME_STEAL];
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guest = cpustat[CPUTIME_GUEST];
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guest_nice = cpustat[CPUTIME_GUEST_NICE];
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seq_printf(p, "cpu%d", i);
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seq_put_decimal_ull(p, " ", nsec_to_clock_t(user));
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seq_put_decimal_ull(p, " ", nsec_to_clock_t(nice));
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seq_put_decimal_ull(p, " ", nsec_to_clock_t(system));
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seq_put_decimal_ull(p, " ", nsec_to_clock_t(idle));
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seq_put_decimal_ull(p, " ", nsec_to_clock_t(iowait));
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seq_put_decimal_ull(p, " ", nsec_to_clock_t(irq));
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seq_put_decimal_ull(p, " ", nsec_to_clock_t(softirq));
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seq_put_decimal_ull(p, " ", nsec_to_clock_t(steal));
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seq_put_decimal_ull(p, " ", nsec_to_clock_t(guest));
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seq_put_decimal_ull(p, " ", nsec_to_clock_t(guest_nice));
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seq_putc(p, '\n');
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}
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seq_put_decimal_ull(p, "intr ", (unsigned long long)sum);
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show_all_irqs(p);
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seq_printf(p,
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"\nctxt %llu\n"
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"btime %llu\n"
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"processes %lu\n"
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"procs_running %u\n"
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"procs_blocked %u\n",
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nr_context_switches(),
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(unsigned long long)boottime.tv_sec,
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total_forks,
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nr_running(),
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nr_iowait());
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seq_put_decimal_ull(p, "softirq ", (unsigned long long)sum_softirq);
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for (i = 0; i < NR_SOFTIRQS; i++)
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seq_put_decimal_ull(p, " ", 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 int size = 1024 + 128 * num_online_cpus();
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/* minimum size to display an interrupt count : 2 bytes */
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size += 2 * nr_irqs;
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return single_open_size(file, show_stat, NULL, size);
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}
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static const struct proc_ops stat_proc_ops = {
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.proc_flags = PROC_ENTRY_PERMANENT,
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.proc_open = stat_open,
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.proc_read_iter = seq_read_iter,
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.proc_lseek = seq_lseek,
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.proc_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, &stat_proc_ops);
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return 0;
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}
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fs_initcall(proc_stat_init);
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