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kernel/time/timer_stats.c
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/* * kernel/time/timer_stats.c * * Collect timer usage statistics. * * Copyright(C) 2006, Red Hat, Inc., Ingo Molnar * Copyright(C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com> * * timer_stats is based on timer_top, a similar functionality which was part of * Con Kolivas dyntick patch set. It was developed by Daniel Petrini at the * Instituto Nokia de Tecnologia - INdT - Manaus. timer_top's design was based * on dynamic allocation of the statistics entries and linear search based * lookup combined with a global lock, rather than the static array, hash * and per-CPU locking which is used by timer_stats. It was written for the * pre hrtimer kernel code and therefore did not take hrtimers into account. * Nevertheless it provided the base for the timer_stats implementation and * was a helpful source of inspiration. Kudos to Daniel and the Nokia folks * for this effort. * * timer_top.c is * Copyright (C) 2005 Instituto Nokia de Tecnologia - INdT - Manaus * Written by Daniel Petrini <d.pensator@gmail.com> * timer_top.c was released under the GNU General Public License version 2 * * We export the addresses and counting of timer functions being called, * the pid and cmdline from the owner process if applicable. * * Start/stop data collection: |
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* # echo [1|0] >/proc/timer_stats |
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* * Display the information collected so far: * # cat /proc/timer_stats * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. */ #include <linux/proc_fs.h> #include <linux/module.h> #include <linux/spinlock.h> #include <linux/sched.h> #include <linux/seq_file.h> #include <linux/kallsyms.h> #include <asm/uaccess.h> /* * This is our basic unit of interest: a timer expiry event identified * by the timer, its start/expire functions and the PID of the task that * started the timer. We count the number of times an event happens: */ struct entry { /* * Hash list: */ struct entry *next; /* * Hash keys: */ void *timer; void *start_func; void *expire_func; pid_t pid; /* * Number of timeout events: */ unsigned long count; |
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unsigned int timer_flag; |
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/* * We save the command-line string to preserve * this information past task exit: */ char comm[TASK_COMM_LEN + 1]; } ____cacheline_aligned_in_smp; /* * Spinlock protecting the tables - not taken during lookup: */ |
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static DEFINE_RAW_SPINLOCK(table_lock); |
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/* * Per-CPU lookup locks for fast hash lookup: */ |
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static DEFINE_PER_CPU(raw_spinlock_t, tstats_lookup_lock); |
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/* * Mutex to serialize state changes with show-stats activities: */ static DEFINE_MUTEX(show_mutex); /* * Collection status, active/inactive: */ |
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int __read_mostly timer_stats_active; |
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/* * Beginning/end timestamps of measurement: */ static ktime_t time_start, time_stop; /* * tstat entry structs only get allocated while collection is * active and never freed during that time - this simplifies * things quite a bit. * * They get freed when a new collection period is started. */ #define MAX_ENTRIES_BITS 10 #define MAX_ENTRIES (1UL << MAX_ENTRIES_BITS) static unsigned long nr_entries; static struct entry entries[MAX_ENTRIES]; static atomic_t overflow_count; |
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/* * The entries are in a hash-table, for fast lookup: */ #define TSTAT_HASH_BITS (MAX_ENTRIES_BITS - 1) #define TSTAT_HASH_SIZE (1UL << TSTAT_HASH_BITS) #define TSTAT_HASH_MASK (TSTAT_HASH_SIZE - 1) #define __tstat_hashfn(entry) \ (((unsigned long)(entry)->timer ^ \ (unsigned long)(entry)->start_func ^ \ (unsigned long)(entry)->expire_func ^ \ (unsigned long)(entry)->pid ) & TSTAT_HASH_MASK) #define tstat_hashentry(entry) (tstat_hash_table + __tstat_hashfn(entry)) static struct entry *tstat_hash_table[TSTAT_HASH_SIZE] __read_mostly; |
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static void reset_entries(void) { nr_entries = 0; memset(entries, 0, sizeof(entries)); memset(tstat_hash_table, 0, sizeof(tstat_hash_table)); atomic_set(&overflow_count, 0); } static struct entry *alloc_entry(void) { if (nr_entries >= MAX_ENTRIES) return NULL; return entries + nr_entries++; } |
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static int match_entries(struct entry *entry1, struct entry *entry2) { return entry1->timer == entry2->timer && entry1->start_func == entry2->start_func && entry1->expire_func == entry2->expire_func && entry1->pid == entry2->pid; } /* * Look up whether an entry matching this item is present * in the hash already. Must be called with irqs off and the * lookup lock held: */ static struct entry *tstat_lookup(struct entry *entry, char *comm) { struct entry **head, *curr, *prev; head = tstat_hashentry(entry); curr = *head; /* * The fastpath is when the entry is already hashed, * we do this with the lookup lock held, but with the * table lock not held: */ while (curr) { if (match_entries(curr, entry)) return curr; curr = curr->next; } /* * Slowpath: allocate, set up and link a new hash entry: */ prev = NULL; curr = *head; |
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raw_spin_lock(&table_lock); |
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/* * Make sure we have not raced with another CPU: */ while (curr) { if (match_entries(curr, entry)) goto out_unlock; prev = curr; curr = curr->next; } curr = alloc_entry(); if (curr) { *curr = *entry; curr->count = 0; |
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curr->next = NULL; |
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memcpy(curr->comm, comm, TASK_COMM_LEN); |
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smp_mb(); /* Ensure that curr is initialized before insert */ |
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if (prev) prev->next = curr; else *head = curr; |
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} out_unlock: |
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raw_spin_unlock(&table_lock); |
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return curr; } /** * timer_stats_update_stats - Update the statistics for a timer. * @timer: pointer to either a timer_list or a hrtimer * @pid: the pid of the task which set up the timer * @startf: pointer to the function which did the timer setup * @timerf: pointer to the timer callback function of the timer * @comm: name of the process which set up the timer * * When the timer is already registered, then the event counter is * incremented. Otherwise the timer is registered in a free slot. */ void timer_stats_update_stats(void *timer, pid_t pid, void *startf, |
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void *timerf, char *comm, unsigned int timer_flag) |
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{ /* |
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* It doesn't matter which lock we take: |
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*/ |
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raw_spinlock_t *lock; |
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struct entry *entry, input; unsigned long flags; |
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if (likely(!timer_stats_active)) |
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return; |
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lock = &per_cpu(tstats_lookup_lock, raw_smp_processor_id()); |
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input.timer = timer; input.start_func = startf; input.expire_func = timerf; input.pid = pid; |
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input.timer_flag = timer_flag; |
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|
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raw_spin_lock_irqsave(lock, flags); |
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if (!timer_stats_active) |
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goto out_unlock; entry = tstat_lookup(&input, comm); if (likely(entry)) entry->count++; else atomic_inc(&overflow_count); out_unlock: |
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raw_spin_unlock_irqrestore(lock, flags); |
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} static void print_name_offset(struct seq_file *m, unsigned long addr) { |
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char symname[KSYM_NAME_LEN]; |
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if (lookup_symbol_name(addr, symname) < 0) |
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seq_printf(m, "<%p>", (void *)addr); |
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else seq_printf(m, "%s", symname); |
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} static int tstats_show(struct seq_file *m, void *v) { struct timespec period; struct entry *entry; unsigned long ms; long events = 0; ktime_t time; int i; mutex_lock(&show_mutex); /* * If still active then calculate up to now: */ |
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if (timer_stats_active) |
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time_stop = ktime_get(); time = ktime_sub(time_stop, time_start); period = ktime_to_timespec(time); ms = period.tv_nsec / 1000000; |
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seq_puts(m, "Timer Stats Version: v0.3 "); |
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seq_printf(m, "Sample period: %ld.%03ld s ", period.tv_sec, ms); if (atomic_read(&overflow_count)) |
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seq_printf(m, "Overflow: %d entries ", atomic_read(&overflow_count)); seq_printf(m, "Collection: %s ", timer_stats_active ? "active" : "inactive"); |
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for (i = 0; i < nr_entries; i++) { entry = entries + i; |
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if (entry->timer_flag & TIMER_STATS_FLAG_DEFERRABLE) { |
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seq_printf(m, "%4luD, %5d %-16s ", |
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entry->count, entry->pid, entry->comm); |
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} else { seq_printf(m, " %4lu, %5d %-16s ", entry->count, entry->pid, entry->comm); } |
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print_name_offset(m, (unsigned long)entry->start_func); seq_puts(m, " ("); print_name_offset(m, (unsigned long)entry->expire_func); seq_puts(m, ") "); events += entry->count; } ms += period.tv_sec * 1000; if (!ms) ms = 1; if (events && period.tv_sec) |
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seq_printf(m, "%ld total events, %ld.%03ld events/sec ", events, events * 1000 / ms, (events * 1000000 / ms) % 1000); |
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else seq_printf(m, "%ld total events ", events); mutex_unlock(&show_mutex); return 0; } /* * After a state change, make sure all concurrent lookup/update * activities have stopped: */ static void sync_access(void) { unsigned long flags; int cpu; for_each_online_cpu(cpu) { |
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raw_spinlock_t *lock = &per_cpu(tstats_lookup_lock, cpu); raw_spin_lock_irqsave(lock, flags); |
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/* nothing */ |
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raw_spin_unlock_irqrestore(lock, flags); |
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} } static ssize_t tstats_write(struct file *file, const char __user *buf, size_t count, loff_t *offs) { char ctl[2]; if (count != 2 || *offs) return -EINVAL; if (copy_from_user(ctl, buf, count)) return -EFAULT; mutex_lock(&show_mutex); switch (ctl[0]) { case '0': |
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if (timer_stats_active) { timer_stats_active = 0; |
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time_stop = ktime_get(); sync_access(); } break; case '1': |
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if (!timer_stats_active) { |
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reset_entries(); time_start = ktime_get(); |
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smp_mb(); |
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timer_stats_active = 1; |
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} break; default: count = -EINVAL; } mutex_unlock(&show_mutex); return count; } static int tstats_open(struct inode *inode, struct file *filp) { return single_open(filp, tstats_show, NULL); } |
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static const struct file_operations tstats_fops = { |
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.open = tstats_open, .read = seq_read, .write = tstats_write, .llseek = seq_lseek, |
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.release = single_release, |
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}; void __init init_timer_stats(void) { int cpu; for_each_possible_cpu(cpu) |
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raw_spin_lock_init(&per_cpu(tstats_lookup_lock, cpu)); |
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} static int __init init_tstats_procfs(void) { struct proc_dir_entry *pe; |
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pe = proc_create("timer_stats", 0644, NULL, &tstats_fops); |
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if (!pe) return -ENOMEM; |
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return 0; } __initcall(init_tstats_procfs); |