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![Dong Zhu](/assets/img/avatar_default.png)
We can enable/disable timer statistics collection via: echo [1|0] > /proc/timers_stats and it would be nice if apps had the ability to check what the current collection status is. This patch adds a 'Collection: active/inactive' line to display the current timer collection status. Also bump up the timer stats version to v0.3. Signed-off-by: Dong Zhu <bluezhudong@gmail.com> Cc: John Stultz <john.stultz@linaro.org> Link: http://lkml.kernel.org/r/20131010075618.GH2139@zhudong.nay.redhat.com [ Improved the changelog and the code. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
425 lines
10 KiB
C
425 lines
10 KiB
C
/*
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* kernel/time/timer_stats.c
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*
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* Collect timer usage statistics.
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*
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* Copyright(C) 2006, Red Hat, Inc., Ingo Molnar
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* Copyright(C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
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*
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* timer_stats is based on timer_top, a similar functionality which was part of
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* Con Kolivas dyntick patch set. It was developed by Daniel Petrini at the
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* Instituto Nokia de Tecnologia - INdT - Manaus. timer_top's design was based
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* on dynamic allocation of the statistics entries and linear search based
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* lookup combined with a global lock, rather than the static array, hash
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* and per-CPU locking which is used by timer_stats. It was written for the
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* pre hrtimer kernel code and therefore did not take hrtimers into account.
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* Nevertheless it provided the base for the timer_stats implementation and
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* was a helpful source of inspiration. Kudos to Daniel and the Nokia folks
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* for this effort.
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*
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* timer_top.c is
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* Copyright (C) 2005 Instituto Nokia de Tecnologia - INdT - Manaus
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* Written by Daniel Petrini <d.pensator@gmail.com>
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* timer_top.c was released under the GNU General Public License version 2
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*
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* We export the addresses and counting of timer functions being called,
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* the pid and cmdline from the owner process if applicable.
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*
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* Start/stop data collection:
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* # echo [1|0] >/proc/timer_stats
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*
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* Display the information collected so far:
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* # cat /proc/timer_stats
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/proc_fs.h>
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#include <linux/module.h>
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#include <linux/spinlock.h>
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#include <linux/sched.h>
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#include <linux/seq_file.h>
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#include <linux/kallsyms.h>
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#include <asm/uaccess.h>
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/*
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* This is our basic unit of interest: a timer expiry event identified
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* by the timer, its start/expire functions and the PID of the task that
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* started the timer. We count the number of times an event happens:
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*/
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struct entry {
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/*
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* Hash list:
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*/
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struct entry *next;
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/*
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* Hash keys:
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*/
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void *timer;
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void *start_func;
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void *expire_func;
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pid_t pid;
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/*
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* Number of timeout events:
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*/
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unsigned long count;
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unsigned int timer_flag;
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/*
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* We save the command-line string to preserve
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* this information past task exit:
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*/
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char comm[TASK_COMM_LEN + 1];
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} ____cacheline_aligned_in_smp;
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/*
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* Spinlock protecting the tables - not taken during lookup:
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*/
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static DEFINE_RAW_SPINLOCK(table_lock);
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/*
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* Per-CPU lookup locks for fast hash lookup:
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*/
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static DEFINE_PER_CPU(raw_spinlock_t, tstats_lookup_lock);
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/*
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* Mutex to serialize state changes with show-stats activities:
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*/
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static DEFINE_MUTEX(show_mutex);
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/*
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* Collection status, active/inactive:
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*/
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int __read_mostly timer_stats_active;
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/*
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* Beginning/end timestamps of measurement:
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*/
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static ktime_t time_start, time_stop;
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/*
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* tstat entry structs only get allocated while collection is
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* active and never freed during that time - this simplifies
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* things quite a bit.
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*
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* They get freed when a new collection period is started.
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*/
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#define MAX_ENTRIES_BITS 10
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#define MAX_ENTRIES (1UL << MAX_ENTRIES_BITS)
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static unsigned long nr_entries;
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static struct entry entries[MAX_ENTRIES];
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static atomic_t overflow_count;
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/*
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* The entries are in a hash-table, for fast lookup:
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*/
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#define TSTAT_HASH_BITS (MAX_ENTRIES_BITS - 1)
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#define TSTAT_HASH_SIZE (1UL << TSTAT_HASH_BITS)
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#define TSTAT_HASH_MASK (TSTAT_HASH_SIZE - 1)
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#define __tstat_hashfn(entry) \
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(((unsigned long)(entry)->timer ^ \
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(unsigned long)(entry)->start_func ^ \
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(unsigned long)(entry)->expire_func ^ \
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(unsigned long)(entry)->pid ) & TSTAT_HASH_MASK)
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#define tstat_hashentry(entry) (tstat_hash_table + __tstat_hashfn(entry))
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static struct entry *tstat_hash_table[TSTAT_HASH_SIZE] __read_mostly;
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static void reset_entries(void)
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{
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nr_entries = 0;
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memset(entries, 0, sizeof(entries));
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memset(tstat_hash_table, 0, sizeof(tstat_hash_table));
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atomic_set(&overflow_count, 0);
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}
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static struct entry *alloc_entry(void)
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{
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if (nr_entries >= MAX_ENTRIES)
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return NULL;
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return entries + nr_entries++;
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}
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static int match_entries(struct entry *entry1, struct entry *entry2)
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{
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return entry1->timer == entry2->timer &&
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entry1->start_func == entry2->start_func &&
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entry1->expire_func == entry2->expire_func &&
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entry1->pid == entry2->pid;
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}
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/*
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* Look up whether an entry matching this item is present
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* in the hash already. Must be called with irqs off and the
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* lookup lock held:
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*/
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static struct entry *tstat_lookup(struct entry *entry, char *comm)
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{
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struct entry **head, *curr, *prev;
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head = tstat_hashentry(entry);
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curr = *head;
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/*
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* The fastpath is when the entry is already hashed,
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* we do this with the lookup lock held, but with the
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* table lock not held:
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*/
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while (curr) {
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if (match_entries(curr, entry))
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return curr;
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curr = curr->next;
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}
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/*
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* Slowpath: allocate, set up and link a new hash entry:
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*/
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prev = NULL;
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curr = *head;
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raw_spin_lock(&table_lock);
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/*
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* Make sure we have not raced with another CPU:
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*/
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while (curr) {
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if (match_entries(curr, entry))
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goto out_unlock;
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prev = curr;
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curr = curr->next;
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}
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curr = alloc_entry();
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if (curr) {
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*curr = *entry;
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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)
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prev->next = curr;
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else
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*head = curr;
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}
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out_unlock:
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raw_spin_unlock(&table_lock);
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return curr;
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}
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/**
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* timer_stats_update_stats - Update the statistics for a timer.
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* @timer: pointer to either a timer_list or a hrtimer
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* @pid: the pid of the task which set up the timer
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* @startf: pointer to the function which did the timer setup
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* @timerf: pointer to the timer callback function of the timer
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* @comm: name of the process which set up the timer
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*
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* When the timer is already registered, then the event counter is
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* incremented. Otherwise the timer is registered in a free slot.
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*/
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void timer_stats_update_stats(void *timer, pid_t pid, void *startf,
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void *timerf, char *comm,
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unsigned int timer_flag)
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{
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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;
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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;
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input.start_func = startf;
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input.expire_func = timerf;
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input.pid = pid;
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input.timer_flag = timer_flag;
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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;
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entry = tstat_lookup(&input, comm);
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if (likely(entry))
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entry->count++;
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else
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atomic_inc(&overflow_count);
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out_unlock:
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raw_spin_unlock_irqrestore(lock, flags);
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}
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static void print_name_offset(struct seq_file *m, unsigned long addr)
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{
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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
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seq_printf(m, "%s", symname);
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}
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static int tstats_show(struct seq_file *m, void *v)
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{
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struct timespec period;
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struct entry *entry;
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unsigned long ms;
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long events = 0;
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ktime_t time;
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int i;
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mutex_lock(&show_mutex);
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/*
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* If still active then calculate up to now:
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*/
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if (timer_stats_active)
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time_stop = ktime_get();
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time = ktime_sub(time_stop, time_start);
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period = ktime_to_timespec(time);
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ms = period.tv_nsec / 1000000;
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seq_puts(m, "Timer Stats Version: v0.3\n");
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seq_printf(m, "Sample period: %ld.%03ld s\n", period.tv_sec, ms);
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if (atomic_read(&overflow_count))
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seq_printf(m, "Overflow: %d entries\n", atomic_read(&overflow_count));
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seq_printf(m, "Collection: %s\n", timer_stats_active ? "active" : "inactive");
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for (i = 0; i < nr_entries; i++) {
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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 {
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seq_printf(m, " %4lu, %5d %-16s ",
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entry->count, entry->pid, entry->comm);
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}
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print_name_offset(m, (unsigned long)entry->start_func);
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seq_puts(m, " (");
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print_name_offset(m, (unsigned long)entry->expire_func);
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seq_puts(m, ")\n");
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events += entry->count;
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}
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ms += period.tv_sec * 1000;
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if (!ms)
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ms = 1;
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if (events && period.tv_sec)
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seq_printf(m, "%ld total events, %ld.%03ld events/sec\n",
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events, events * 1000 / ms,
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(events * 1000000 / ms) % 1000);
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else
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seq_printf(m, "%ld total events\n", events);
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mutex_unlock(&show_mutex);
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return 0;
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}
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/*
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* After a state change, make sure all concurrent lookup/update
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* activities have stopped:
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*/
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static void sync_access(void)
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{
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unsigned long flags;
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int cpu;
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for_each_online_cpu(cpu) {
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raw_spinlock_t *lock = &per_cpu(tstats_lookup_lock, cpu);
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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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}
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}
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static ssize_t tstats_write(struct file *file, const char __user *buf,
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size_t count, loff_t *offs)
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{
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char ctl[2];
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if (count != 2 || *offs)
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return -EINVAL;
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if (copy_from_user(ctl, buf, count))
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return -EFAULT;
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mutex_lock(&show_mutex);
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switch (ctl[0]) {
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case '0':
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if (timer_stats_active) {
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timer_stats_active = 0;
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time_stop = ktime_get();
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sync_access();
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}
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break;
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case '1':
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if (!timer_stats_active) {
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reset_entries();
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time_start = ktime_get();
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smp_mb();
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timer_stats_active = 1;
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}
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break;
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default:
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count = -EINVAL;
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}
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mutex_unlock(&show_mutex);
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return count;
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}
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static int tstats_open(struct inode *inode, struct file *filp)
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{
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return single_open(filp, tstats_show, NULL);
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}
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static const struct file_operations tstats_fops = {
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.open = tstats_open,
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.read = seq_read,
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.write = tstats_write,
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.llseek = seq_lseek,
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.release = single_release,
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};
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void __init init_timer_stats(void)
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{
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int cpu;
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for_each_possible_cpu(cpu)
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raw_spin_lock_init(&per_cpu(tstats_lookup_lock, cpu));
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}
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static int __init init_tstats_procfs(void)
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{
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struct proc_dir_entry *pe;
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pe = proc_create("timer_stats", 0644, NULL, &tstats_fops);
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if (!pe)
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return -ENOMEM;
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return 0;
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}
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__initcall(init_tstats_procfs);
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