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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
119 lines
3.0 KiB
C
119 lines
3.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_KERNEL_STAT_H
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#define _LINUX_KERNEL_STAT_H
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#include <linux/smp.h>
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#include <linux/threads.h>
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#include <linux/percpu.h>
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#include <linux/cpumask.h>
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#include <linux/interrupt.h>
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#include <linux/sched.h>
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#include <linux/vtime.h>
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#include <asm/irq.h>
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/*
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* 'kernel_stat.h' contains the definitions needed for doing
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* some kernel statistics (CPU usage, context switches ...),
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* used by rstatd/perfmeter
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*/
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enum cpu_usage_stat {
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CPUTIME_USER,
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CPUTIME_NICE,
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CPUTIME_SYSTEM,
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CPUTIME_SOFTIRQ,
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CPUTIME_IRQ,
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CPUTIME_IDLE,
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CPUTIME_IOWAIT,
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CPUTIME_STEAL,
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CPUTIME_GUEST,
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CPUTIME_GUEST_NICE,
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NR_STATS,
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};
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struct kernel_cpustat {
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u64 cpustat[NR_STATS];
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};
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struct kernel_stat {
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unsigned long irqs_sum;
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unsigned int softirqs[NR_SOFTIRQS];
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};
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DECLARE_PER_CPU(struct kernel_stat, kstat);
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DECLARE_PER_CPU(struct kernel_cpustat, kernel_cpustat);
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/* Must have preemption disabled for this to be meaningful. */
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#define kstat_this_cpu this_cpu_ptr(&kstat)
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#define kcpustat_this_cpu this_cpu_ptr(&kernel_cpustat)
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#define kstat_cpu(cpu) per_cpu(kstat, cpu)
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#define kcpustat_cpu(cpu) per_cpu(kernel_cpustat, cpu)
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extern unsigned long long nr_context_switches(void);
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extern unsigned int kstat_irqs_cpu(unsigned int irq, int cpu);
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extern void kstat_incr_irq_this_cpu(unsigned int irq);
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static inline void kstat_incr_softirqs_this_cpu(unsigned int irq)
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{
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__this_cpu_inc(kstat.softirqs[irq]);
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}
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static inline unsigned int kstat_softirqs_cpu(unsigned int irq, int cpu)
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{
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return kstat_cpu(cpu).softirqs[irq];
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}
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/*
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* Number of interrupts per specific IRQ source, since bootup
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*/
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extern unsigned int kstat_irqs_usr(unsigned int irq);
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/*
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* Number of interrupts per cpu, since bootup
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*/
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static inline unsigned int kstat_cpu_irqs_sum(unsigned int cpu)
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{
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return kstat_cpu(cpu).irqs_sum;
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}
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#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
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extern u64 kcpustat_field(struct kernel_cpustat *kcpustat,
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enum cpu_usage_stat usage, int cpu);
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extern void kcpustat_cpu_fetch(struct kernel_cpustat *dst, int cpu);
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#else
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static inline u64 kcpustat_field(struct kernel_cpustat *kcpustat,
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enum cpu_usage_stat usage, int cpu)
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{
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return kcpustat->cpustat[usage];
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}
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static inline void kcpustat_cpu_fetch(struct kernel_cpustat *dst, int cpu)
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{
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*dst = kcpustat_cpu(cpu);
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}
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#endif
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extern void account_user_time(struct task_struct *, u64);
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extern void account_guest_time(struct task_struct *, u64);
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extern void account_system_time(struct task_struct *, int, u64);
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extern void account_system_index_time(struct task_struct *, u64,
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enum cpu_usage_stat);
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extern void account_steal_time(u64);
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extern void account_idle_time(u64);
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extern u64 get_idle_time(struct kernel_cpustat *kcs, int cpu);
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#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
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static inline void account_process_tick(struct task_struct *tsk, int user)
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{
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vtime_flush(tsk);
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}
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#else
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extern void account_process_tick(struct task_struct *, int user);
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#endif
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extern void account_idle_ticks(unsigned long ticks);
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#endif /* _LINUX_KERNEL_STAT_H */
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