![Anton Blanchard](/assets/img/avatar_default.png)
When using /proc/timer_stats on ppc64 I noticed the events/sec field wasnt accurate. Sometimes the integer part was incorrect due to rounding (we werent taking the fractional seconds into consideration). The fraction part is also wrong, we need to pad the printf statement and take the bottom three digits of 1000 times the value. Signed-off-by: Anton Blanchard <anton@samba.org> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
427 lines
9.8 KiB
C
427 lines
9.8 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_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(spinlock_t, 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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static int __read_mostly 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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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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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 doesnt matter which lock we take:
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*/
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spinlock_t *lock;
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struct entry *entry, input;
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unsigned long flags;
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if (likely(!active))
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return;
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lock = &per_cpu(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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spin_lock_irqsave(lock, flags);
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if (!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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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 (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: v0.2\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",
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atomic_read(&overflow_count));
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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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spin_lock_irqsave(&per_cpu(lookup_lock, cpu), flags);
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/* nothing */
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spin_unlock_irqrestore(&per_cpu(lookup_lock, cpu), 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 (active) {
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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 (!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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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 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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spin_lock_init(&per_cpu(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 = create_proc_entry("timer_stats", 0644, NULL);
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if (!pe)
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return -ENOMEM;
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pe->proc_fops = &tstats_fops;
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return 0;
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}
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__initcall(init_tstats_procfs);
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