kernel/trace/trace_unlikely.c

   1 /*
   2  * unlikely profiler
   3  *
   4  * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
   5  */
   6 #include <linux/kallsyms.h>
   7 #include <linux/seq_file.h>
   8 #include <linux/spinlock.h>
   9 #include <linux/debugfs.h>
  10 #include <linux/uaccess.h>
  11 #include <linux/module.h>
  12 #include <linux/ftrace.h>
  13 #include <linux/hash.h>
  14 #include <linux/fs.h>
  15 #include <asm/local.h>
  16 #include "trace.h"
  17
  18 #ifdef CONFIG_UNLIKELY_TRACER
  19
  20 static int unlikely_tracing_enabled __read_mostly;
  21 static DEFINE_MUTEX(unlikely_tracing_mutex);
  22 static struct trace_array *unlikely_tracer;
  23
  24 static void
  25 probe_likely_condition(struct ftrace_likely_data *f, int val, int expect)
  26 {
  27         struct trace_array *tr = unlikely_tracer;
  28         struct ring_buffer_event *event;
  29         struct trace_unlikely *entry;
  30         unsigned long flags, irq_flags;
  31         int cpu, pc;
  32         const char *p;
  33
  34         /*
  35          * I would love to save just the ftrace_likely_data pointer, but
  36          * this code can also be used by modules. Ugly things can happen
  37          * if the module is unloaded, and then we go and read the
  38          * pointer.  This is slower, but much safer.
  39          */
  40
  41         if (unlikely(!tr))
  42                 return;
  43
  44         local_irq_save(flags);
  45         cpu = raw_smp_processor_id();
  46         if (atomic_inc_return(&tr->data[cpu]->disabled) != 1)
  47                 goto out;
  48
  49         event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry),
  50                                          &irq_flags);
  51         if (!event)
  52                 goto out;
  53
  54         pc = preempt_count();
  55         entry   = ring_buffer_event_data(event);
  56         tracing_generic_entry_update(&entry->ent, flags, pc);
  57         entry->ent.type         = TRACE_UNLIKELY;
  58
  59         /* Strip off the path, only save the file */
  60         p = f->file + strlen(f->file);
  61         while (p >= f->file && *p != '/')
  62                 p--;
  63         p++;
  64
  65         strncpy(entry->func, f->func, TRACE_FUNC_SIZE);
  66         strncpy(entry->file, p, TRACE_FILE_SIZE);
  67         entry->func[TRACE_FUNC_SIZE] = 0;
  68         entry->file[TRACE_FILE_SIZE] = 0;
  69         entry->line = f->line;
  70         entry->correct = val == expect;
  71
  72         ring_buffer_unlock_commit(tr->buffer, event, irq_flags);
  73
  74  out:
  75         atomic_dec(&tr->data[cpu]->disabled);
  76         local_irq_restore(flags);
  77 }
  78
  79 static inline
  80 void trace_likely_condition(struct ftrace_likely_data *f, int val, int expect)
  81 {
  82         if (!unlikely_tracing_enabled)
  83                 return;
  84
  85         probe_likely_condition(f, val, expect);
  86 }
  87
  88 int enable_unlikely_tracing(struct trace_array *tr)
  89 {
  90         int ret = 0;
  91
  92         mutex_lock(&unlikely_tracing_mutex);
  93         unlikely_tracer = tr;
  94         /*
  95          * Must be seen before enabling. The reader is a condition
  96          * where we do not need a matching rmb()
  97          */
  98         smp_wmb();
  99         unlikely_tracing_enabled++;
 100         mutex_unlock(&unlikely_tracing_mutex);
 101
 102         return ret;
 103 }
 104
 105 void disable_unlikely_tracing(void)
 106 {
 107         mutex_lock(&unlikely_tracing_mutex);
 108
 109         if (!unlikely_tracing_enabled)
 110                 goto out_unlock;
 111
 112         unlikely_tracing_enabled--;
 113
 114  out_unlock:
 115         mutex_unlock(&unlikely_tracing_mutex);
 116 }
 117 #else
 118 static inline
 119 void trace_likely_condition(struct ftrace_likely_data *f, int val, int expect)
 120 {
 121 }
 122 #endif /* CONFIG_UNLIKELY_TRACER */
 123
 124 void ftrace_likely_update(struct ftrace_likely_data *f, int val, int expect)
 125 {
 126         /*
 127          * I would love to have a trace point here instead, but the
 128          * trace point code is so inundated with unlikely and likely
 129          * conditions that the recursive nightmare that exists is too
 130          * much to try to get working. At least for now.
 131          */
 132         trace_likely_condition(f, val, expect);
 133
 134         /* FIXME: Make this atomic! */
 135         if (val == expect)
 136                 f->correct++;
 137         else
 138                 f->incorrect++;
 139 }
 140 EXPORT_SYMBOL(ftrace_likely_update);
 141
 142 struct ftrace_pointer {
 143         void            *start;
 144         void            *stop;
 145 };
 146
 147 static void *
 148 t_next(struct seq_file *m, void *v, loff_t *pos)
 149 {
 150         struct ftrace_pointer *f = m->private;
 151         struct ftrace_likely_data *p = v;
 152
 153         (*pos)++;
 154
 155         if (v == (void *)1)
 156                 return f->start;
 157
 158         ++p;
 159
 160         if ((void *)p >= (void *)f->stop)
 161                 return NULL;
 162
 163         return p;
 164 }
 165
 166 static void *t_start(struct seq_file *m, loff_t *pos)
 167 {
 168         void *t = (void *)1;
 169         loff_t l = 0;
 170
 171         for (; t && l < *pos; t = t_next(m, t, &l))
 172                 ;
 173
 174         return t;
 175 }
 176
 177 static void t_stop(struct seq_file *m, void *p)
 178 {
 179 }
 180
 181 static int t_show(struct seq_file *m, void *v)
 182 {
 183         struct ftrace_likely_data *p = v;
 184         const char *f;
 185         unsigned long percent;
 186
 187         if (v == (void *)1) {
 188                 seq_printf(m, " correct incorrect  %% "
 189                               "       Function                "
 190                               "  File              Line\n"
 191                               " ------- ---------  - "
 192                               "       --------                "
 193                               "  ----              ----\n");
 194                 return 0;
 195         }
 196
 197         /* Only print the file, not the path */
 198         f = p->file + strlen(p->file);
 199         while (f >= p->file && *f != '/')
 200                 f--;
 201         f++;
 202
 203         if (p->correct) {
 204                 percent = p->incorrect * 100;
 205                 percent /= p->correct + p->incorrect;
 206         } else
 207                 percent = p->incorrect ? 100 : 0;
 208
 209         seq_printf(m, "%8lu %8lu %3lu ", p->correct, p->incorrect, percent);
 210         seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
 211         return 0;
 212 }
 213
 214 static struct seq_operations tracing_likely_seq_ops = {
 215         .start          = t_start,
 216         .next           = t_next,
 217         .stop           = t_stop,
 218         .show           = t_show,
 219 };
 220
 221 static int tracing_likely_open(struct inode *inode, struct file *file)
 222 {
 223         int ret;
 224
 225         ret = seq_open(file, &tracing_likely_seq_ops);
 226         if (!ret) {
 227                 struct seq_file *m = file->private_data;
 228                 m->private = (void *)inode->i_private;
 229         }
 230
 231         return ret;
 232 }
 233
 234 static struct file_operations tracing_likely_fops = {
 235         .open           = tracing_likely_open,
 236         .read           = seq_read,
 237         .llseek         = seq_lseek,
 238 };
 239
 240 extern unsigned long __start_likely_profile[];
 241 extern unsigned long __stop_likely_profile[];
 242 extern unsigned long __start_unlikely_profile[];
 243 extern unsigned long __stop_unlikely_profile[];
 244
 245 static struct ftrace_pointer ftrace_likely_pos = {
 246         .start                  = __start_likely_profile,
 247         .stop                   = __stop_likely_profile,
 248 };
 249
 250 static struct ftrace_pointer ftrace_unlikely_pos = {
 251         .start                  = __start_unlikely_profile,
 252         .stop                   = __stop_unlikely_profile,
 253 };
 254
 255 static __init int ftrace_unlikely_init(void)
 256 {
 257         struct dentry *d_tracer;
 258         struct dentry *entry;
 259
 260         d_tracer = tracing_init_dentry();
 261
 262         entry = debugfs_create_file("profile_likely", 0444, d_tracer,
 263                                     &ftrace_likely_pos,
 264                                     &tracing_likely_fops);
 265         if (!entry)
 266                 pr_warning("Could not create debugfs 'profile_likely' entry\n");
 267
 268         entry = debugfs_create_file("profile_unlikely", 0444, d_tracer,
 269                                     &ftrace_unlikely_pos,
 270                                     &tracing_likely_fops);
 271         if (!entry)
 272                 pr_warning("Could not create debugfs"
 273                            " 'profile_unlikely' entry\n");
 274
 275         return 0;
 276 }
 277
 278 device_initcall(ftrace_unlikely_init);