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    Subject[PATCH v2][RFC] ftrace: function oprofiler
    [
    Still not ready for inclussion. (well, not tested enough)

    Changes since v1:

    I took a more casual look over the code and realized how bad
    I can write when I'm half asleep. I fixed several nasty
    (and stupid) race conditions. I still did not spend that
    much time on this code, but it should be much safer.

    One of the changes was to turn the counter into an atomic
    int. This means that we can overflow after a function was hit
    over 4 billion times. I added a check for this and the hash
    will add a '!' if the overflow happens. The final version of
    this code will probably use atomic_long, but that is still
    only 32bits on a i386.

    Also fixed the cut and paste error that Frederic pointed out.
    ]


    This is a function profiler to count the number of times a function is hit.
    It creates two files:

    /debugfs/tracing/ftrace_profile_enable
    /debugfs/tracing/ftrace_profile

    For example, to run this I did this as soon as I was able to log in.

    # echo 1 > /debug/tracing/ftrace_profile_enable

    [ waited a while for the rest of the boot process to run. ]

    # echo 0 > /debug/tracing/ftrace_profile_enable

    And then I was able to get a list of counts functions were hit.

    # cat /debug/tracing/ftrace_profile | head
    entries: 2274
    overruns: 0
    COUNT FUNCTION
    7628 : dnotify_parent+0xd/0x78
    10101 : hrtimer_get_next_event+0x11/0xc7
    17937 : inotify_dentry_parent_queue_event+0x11/0x94
    17952 : inotify_inode_queue_event+0x11/0xe1
    10103 : rcu_needs_cpu+0x4/0x53
    1 : printk_needs_cpu+0x4/0x27
    7314 : printk_needs_cpu+0x4/0x27


    I preallocate 5000 entries (later this needs to be configurable).
    If we hit more than 5000 functions, they are counted in the overruns.

    I'm also able to use sort to get the top 20 hits:

    # cat /debug/tracing/ftrace_profile | sort -brn | head -20
    280075 : __rcu_read_unlock+0xb/0xa2
    280065 : __rcu_read_lock+0x11/0xb3
    262811 : dput+0x7/0x162
    138868 : path_put+0x9/0x35
    117843 : __phys_addr+0x4/0x39
    116320 : current_kernel_time+0x8/0x34
    111272 : kfree+0x11/0xda
    101832 : unroll_tree_refs+0x11/0xb4
    101769 : audit_syscall_exit+0x11/0x312
    101702 : audit_syscall_entry+0x11/0x181
    90910 : set_normalized_timespec+0x4/0x38
    88359 : getnstimeofday+0x7/0x9e
    88309 : ktime_get_ts+0x7/0x53
    85135 : kmem_cache_free+0x11/0xb9
    83917 : ktime_get+0x8/0x47
    51756 : fget+0x7/0x83
    48623 : mntput_no_expire+0x11/0x140
    46224 : vm_normal_page+0x4/0x2c
    41200 : put_page+0xd/0xf5
    39938 : sys_fcntl+0x11/0x344


    Signed-off-by: Steven Rostedt <srostedt@redhat.com>
    ---
    kernel/trace/Kconfig | 11 +
    kernel/trace/Makefile | 1
    kernel/trace/trace_oprofile.c | 361 ++++++++++++++++++++++++++++++++++++++++++
    3 files changed, 373 insertions(+)

    Index: linux-tip.git/kernel/trace/trace_oprofile.c
    ===================================================================
    --- /dev/null 1970-01-01 00:00:00.000000000 +0000
    +++ linux-tip.git/kernel/trace/trace_oprofile.c 2008-10-25 20:48:03.000000000 -0400
    @@ -0,0 +1,361 @@
    +/*
    + * Function profiler
    + *
    + * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
    + */
    +#include <linux/kallsyms.h>
    +#include <linux/seq_file.h>
    +#include <linux/spinlock.h>
    +#include <linux/debugfs.h>
    +#include <linux/uaccess.h>
    +#include <linux/module.h>
    +#include <linux/ftrace.h>
    +#include <linux/hash.h>
    +#include <linux/fs.h>
    +#include <asm/local.h>
    +#include "trace.h"
    +
    +#define FTRACE_PROFILE_HASHBITS 10
    +#define FTRACE_PROFILE_HASHSIZE (1<<FTRACE_PROFILE_HASHBITS)
    +
    +static DEFINE_PER_CPU(local_t, trace_active);
    +static int ftrace_profile_enabled;
    +
    +struct ftrace_node {
    + struct hlist_node node;
    + unsigned long ip;
    + atomic_t count;
    + int overflow;
    +};
    +
    +static struct hlist_head function_hash[FTRACE_PROFILE_HASHSIZE];
    +
    +/* TODO: make user configurable */
    +static int ftrace_hash_size = 5000;
    +static int ftrace_hash_occupied;
    +static int ftrace_hash_overrun;
    +
    +static struct ftrace_node *ftrace_node_list;
    +static struct ftrace_node *ftrace_free_node;
    +
    +static raw_spinlock_t ftrace_profile_lock =
    + (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
    +
    +static int
    +ftrace_profile_alloc_hash_list(void)
    +{
    + /* FIXME: size may be too much for kmalloc */
    + ftrace_node_list = kzalloc(sizeof(struct ftrace_node) *
    + ftrace_hash_size, GFP_KERNEL);
    + if (!ftrace_node_list)
    + return -ENOMEM;
    +
    + ftrace_free_node = ftrace_node_list;
    +
    + return 0;
    +}
    +
    +static void
    +ftrace_profile_init_hash(void)
    +{
    + ftrace_free_node = ftrace_node_list;
    + memset(ftrace_node_list, 0, sizeof(*ftrace_node_list) *
    + ftrace_hash_size);
    + memset(function_hash, 0, sizeof(function_hash));
    +}
    +
    +static void
    +ftrace_profile_free_hash_list(void)
    +{
    + kfree(ftrace_node_list);
    +
    + ftrace_node_list = ftrace_free_node = NULL;
    +}
    +
    +static struct ftrace_node *
    +ftrace_profile_alloc_node(void)
    +{
    + if (ftrace_hash_occupied >= ftrace_hash_size)
    + return NULL;
    +
    + ftrace_hash_occupied++;
    +
    + return ftrace_free_node++;
    +}
    +
    +static struct ftrace_node *
    +ftrace_ip_in_hash(unsigned long ip, unsigned long key)
    +{
    + struct ftrace_node *p;
    + struct hlist_node *t;
    +
    + hlist_for_each_entry_rcu(p, t, &function_hash[key], node) {
    + if (p->ip == ip)
    + return p;
    + }
    +
    + return NULL;
    +}
    +
    +static inline void
    +ftrace_add_hash(struct ftrace_node *node, unsigned long key)
    +{
    + hlist_add_head_rcu(&node->node, &function_hash[key]);
    +}
    +
    +static void
    +ftrace_profile_trace_call(unsigned long ip, unsigned long parent_ip)
    +{
    + struct ftrace_node *p;
    + int cpu, resched;
    + unsigned long key;
    + unsigned long before, after;
    +
    + if (unlikely(!ftrace_enabled || !ftrace_profile_enabled))
    + return;
    +
    + resched = need_resched();
    + preempt_disable_notrace();
    +
    + cpu = raw_smp_processor_id();
    + if (local_inc_return(&per_cpu(trace_active, cpu)) != 1)
    + goto out;
    +
    + key = hash_long(ip, FTRACE_PROFILE_HASHBITS);
    + p = ftrace_ip_in_hash(ip, key);
    +
    + if (!p) {
    + unsigned long flags;
    +
    + local_irq_save(flags);
    + __raw_spin_lock(&ftrace_profile_lock);
    +
    + /* Make sure it was not added on another CPU */
    + p = ftrace_ip_in_hash(ip, key);
    + if (p)
    + goto unlock;
    +
    + p = ftrace_profile_alloc_node();
    + if (!p) {
    + ftrace_hash_overrun++;
    + __raw_spin_unlock(&ftrace_profile_lock);
    + local_irq_restore(flags);
    + goto out;
    + }
    + p->ip = ip;
    + ftrace_add_hash(p, key);
    +
    + unlock:
    + __raw_spin_unlock(&ftrace_profile_lock);
    + local_irq_restore(flags);
    + }
    +
    + if (p->overflow)
    + goto out;
    +
    + before = atomic_read(&p->count);
    + after = atomic_inc_return(&p->count);
    + if (before > after)
    + p->overflow = 1;
    +
    + out:
    + local_dec(&per_cpu(trace_active, cpu));
    + /* prevent recursion in schedule */
    + if (resched)
    + preempt_enable_no_resched_notrace();
    + else
    + preempt_enable_notrace();
    +}
    +
    +static struct ftrace_ops trace_ops __read_mostly =
    +{
    + .func = ftrace_profile_trace_call,
    +};
    +
    +static void *
    +t_next(struct seq_file *m, void *v, loff_t *pos)
    +{
    + long i = (long)m->private;
    +
    + (*pos)++;
    +
    + i++;
    +
    + if (i >= ftrace_hash_occupied)
    + return NULL;
    +
    + m->private = (void *)i;
    +
    + return &m->private;
    +}
    +
    +static void *t_start(struct seq_file *m, loff_t *pos)
    +{
    + void *t = &m->private;
    + loff_t l = 0;
    +
    + local_irq_disable();
    +
    + for (; t && l < *pos; t = t_next(m, t, &l))
    + ;
    +
    + return t;
    +}
    +
    +static void t_stop(struct seq_file *m, void *p)
    +{
    + local_irq_enable();
    +}
    +
    +static int trace_lookup_hash(struct seq_file *m, long i)
    +{
    + unsigned long addr = ftrace_node_list[i].ip;
    +#ifdef CONFIG_KALLSYMS
    + char str[KSYM_SYMBOL_LEN];
    +
    + sprint_symbol(str, addr);
    +
    + return seq_printf(m, "%s\n", str);
    +#else
    + return seq_printf(m, "%p\n", (void*)addr);
    +#endif
    +}
    +
    +static int t_show(struct seq_file *m, void *v)
    +{
    + long i = *(long *)v;
    +
    + if (i < 0) {
    + seq_printf(m, "entries: %d\n", ftrace_hash_occupied);
    + seq_printf(m, "overruns: %d\n", ftrace_hash_overrun);
    +
    + seq_printf(m, " COUNT FUNCTION\n");
    + return 0;
    + }
    +
    + if (i >= ftrace_hash_occupied)
    + return 0;
    +
    + seq_printf(m, " %8u%c : ",
    + atomic_read(&ftrace_node_list[i].count),
    + ftrace_node_list[i].overflow ? '!' : ' ');
    + trace_lookup_hash(m, i);
    +
    + return 0;
    +}
    +
    +static struct seq_operations ftrace_profile_seq_ops = {
    + .start = t_start,
    + .next = t_next,
    + .stop = t_stop,
    + .show = t_show,
    +};
    +
    +static int ftrace_profile_open(struct inode *inode, struct file *file)
    +{
    + int ret;
    +
    + ret = seq_open(file, &ftrace_profile_seq_ops);
    + if (!ret) {
    + struct seq_file *m = file->private_data;
    + m->private = (void *)-1;
    + }
    +
    + return ret;
    +}
    +
    +static struct file_operations ftrace_profile_fops = {
    + .open = ftrace_profile_open,
    + .read = seq_read,
    + .llseek = seq_lseek,
    +};
    +
    +static ssize_t
    +ftrace_profile_enable_read(struct file *filp, char __user *ubuf,
    + size_t cnt, loff_t *ppos)
    +{
    + char buf[64];
    + int r;
    +
    + r = sprintf(buf, "%d\n", ftrace_profile_enabled);
    + return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
    +}
    +
    +static ssize_t
    +ftrace_profile_enable_write(struct file *filp, const char __user *ubuf,
    + size_t cnt, loff_t *ppos)
    +{
    + char buf[64];
    + long val;
    + int ret;
    +
    + if (!ftrace_node_list)
    + return -ENODEV;
    +
    + if (cnt >= sizeof(buf))
    + return -EINVAL;
    +
    + if (copy_from_user(&buf, ubuf, cnt))
    + return -EFAULT;
    +
    + buf[cnt] = 0;
    +
    + ret = strict_strtoul(buf, 10, &val);
    + if (ret < 0)
    + return ret;
    +
    + val = !!val;
    +
    + if (val == ftrace_profile_enabled)
    + goto out;
    +
    + if (val) {
    + /* start it up */
    + ftrace_profile_init_hash();
    + register_ftrace_function(&trace_ops);
    + ftrace_profile_enabled = 1;
    + } else {
    + ftrace_profile_enabled = 0;
    + unregister_ftrace_function(&trace_ops);
    + }
    +
    + out:
    + filp->f_pos += cnt;
    +
    + return cnt;
    +}
    +
    +static struct file_operations ftrace_profile_enable_fops = {
    + .open = tracing_open_generic,
    + .read = ftrace_profile_enable_read,
    + .write = ftrace_profile_enable_write,
    +};
    +
    +
    +static __init int ftrace_profile_init(void)
    +{
    + struct dentry *d_tracer;
    + struct dentry *entry;
    + int ret;
    +
    + ret = ftrace_profile_alloc_hash_list();
    + if (ret)
    + return ret;
    +
    + d_tracer = tracing_init_dentry();
    +
    + entry = debugfs_create_file("ftrace_profile_enable", 0644, d_tracer,
    + NULL, &ftrace_profile_enable_fops);
    + if (!entry)
    + pr_warning("Could not create debugfs 'ftrace_profile_enable' entry\n");
    +
    + entry = debugfs_create_file("ftrace_profile", 0444, d_tracer,
    + NULL, &ftrace_profile_fops);
    + if (!entry)
    + pr_warning("Could not create debugfs 'ftrace_profile' entry\n");
    +
    +
    + return 0;
    +}
    +
    +device_initcall(ftrace_profile_init);
    Index: linux-tip.git/kernel/trace/Kconfig
    ===================================================================
    --- linux-tip.git.orig/kernel/trace/Kconfig 2008-10-23 12:55:37.000000000 -0400
    +++ linux-tip.git/kernel/trace/Kconfig 2008-10-25 11:50:18.000000000 -0400
    @@ -156,6 +156,17 @@ config STACK_TRACER

    Say N if unsure.

    +config FUNCTION_PROFILER
    + bool "Trace function profiler"
    + depends on HAVE_FUNCTION_TRACER
    + depends on DEBUG_KERNEL
    + select FUNCTION_TRACER
    + help
    + This special tracer that makes a histogram of all the functions
    + that it encounters.
    +
    + Say N if unsure.
    +
    config DYNAMIC_FTRACE
    bool "enable/disable ftrace tracepoints dynamically"
    depends on FUNCTION_TRACER
    Index: linux-tip.git/kernel/trace/Makefile
    ===================================================================
    --- linux-tip.git.orig/kernel/trace/Makefile 2008-10-23 12:55:37.000000000 -0400
    +++ linux-tip.git/kernel/trace/Makefile 2008-10-25 00:58:07.000000000 -0400
    @@ -22,6 +22,7 @@ obj-$(CONFIG_PREEMPT_TRACER) += trace_ir
    obj-$(CONFIG_SCHED_TRACER) += trace_sched_wakeup.o
    obj-$(CONFIG_NOP_TRACER) += trace_nop.o
    obj-$(CONFIG_STACK_TRACER) += trace_stack.o
    +obj-$(CONFIG_FUNCTION_PROFILER) += trace_oprofile.o
    obj-$(CONFIG_MMIOTRACE) += trace_mmiotrace.o
    obj-$(CONFIG_BOOT_TRACER) += trace_boot.o




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