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Linux/kernel/trace/trace_branch.c

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  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/irqflags.h>
 10 #include <linux/debugfs.h>
 11 #include <linux/uaccess.h>
 12 #include <linux/module.h>
 13 #include <linux/ftrace.h>
 14 #include <linux/hash.h>
 15 #include <linux/fs.h>
 16 #include <asm/local.h>
 17 
 18 #include "trace.h"
 19 #include "trace_stat.h"
 20 #include "trace_output.h"
 21 
 22 #ifdef CONFIG_BRANCH_TRACER
 23 
 24 static struct tracer branch_trace;
 25 static int branch_tracing_enabled __read_mostly;
 26 static DEFINE_MUTEX(branch_tracing_mutex);
 27 
 28 static struct trace_array *branch_tracer;
 29 
 30 static void
 31 probe_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 32 {
 33         struct ftrace_event_call *call = &event_branch;
 34         struct trace_array *tr = branch_tracer;
 35         struct trace_array_cpu *data;
 36         struct ring_buffer_event *event;
 37         struct trace_branch *entry;
 38         struct ring_buffer *buffer;
 39         unsigned long flags;
 40         int pc;
 41         const char *p;
 42 
 43         if (current->trace_recursion & TRACE_BRANCH_BIT)
 44                 return;
 45 
 46         /*
 47          * I would love to save just the ftrace_likely_data pointer, but
 48          * this code can also be used by modules. Ugly things can happen
 49          * if the module is unloaded, and then we go and read the
 50          * pointer.  This is slower, but much safer.
 51          */
 52 
 53         if (unlikely(!tr))
 54                 return;
 55 
 56         raw_local_irq_save(flags);
 57         current->trace_recursion |= TRACE_BRANCH_BIT;
 58         data = this_cpu_ptr(tr->trace_buffer.data);
 59         if (atomic_read(&data->disabled))
 60                 goto out;
 61 
 62         pc = preempt_count();
 63         buffer = tr->trace_buffer.buffer;
 64         event = trace_buffer_lock_reserve(buffer, TRACE_BRANCH,
 65                                           sizeof(*entry), flags, pc);
 66         if (!event)
 67                 goto out;
 68 
 69         entry   = ring_buffer_event_data(event);
 70 
 71         /* Strip off the path, only save the file */
 72         p = f->file + strlen(f->file);
 73         while (p >= f->file && *p != '/')
 74                 p--;
 75         p++;
 76 
 77         strncpy(entry->func, f->func, TRACE_FUNC_SIZE);
 78         strncpy(entry->file, p, TRACE_FILE_SIZE);
 79         entry->func[TRACE_FUNC_SIZE] = 0;
 80         entry->file[TRACE_FILE_SIZE] = 0;
 81         entry->line = f->line;
 82         entry->correct = val == expect;
 83 
 84         if (!filter_check_discard(call, entry, buffer, event))
 85                 __buffer_unlock_commit(buffer, event);
 86 
 87  out:
 88         current->trace_recursion &= ~TRACE_BRANCH_BIT;
 89         raw_local_irq_restore(flags);
 90 }
 91 
 92 static inline
 93 void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
 94 {
 95         if (!branch_tracing_enabled)
 96                 return;
 97 
 98         probe_likely_condition(f, val, expect);
 99 }
100 
101 int enable_branch_tracing(struct trace_array *tr)
102 {
103         mutex_lock(&branch_tracing_mutex);
104         branch_tracer = tr;
105         /*
106          * Must be seen before enabling. The reader is a condition
107          * where we do not need a matching rmb()
108          */
109         smp_wmb();
110         branch_tracing_enabled++;
111         mutex_unlock(&branch_tracing_mutex);
112 
113         return 0;
114 }
115 
116 void disable_branch_tracing(void)
117 {
118         mutex_lock(&branch_tracing_mutex);
119 
120         if (!branch_tracing_enabled)
121                 goto out_unlock;
122 
123         branch_tracing_enabled--;
124 
125  out_unlock:
126         mutex_unlock(&branch_tracing_mutex);
127 }
128 
129 static void start_branch_trace(struct trace_array *tr)
130 {
131         enable_branch_tracing(tr);
132 }
133 
134 static void stop_branch_trace(struct trace_array *tr)
135 {
136         disable_branch_tracing();
137 }
138 
139 static int branch_trace_init(struct trace_array *tr)
140 {
141         start_branch_trace(tr);
142         return 0;
143 }
144 
145 static void branch_trace_reset(struct trace_array *tr)
146 {
147         stop_branch_trace(tr);
148 }
149 
150 static enum print_line_t trace_branch_print(struct trace_iterator *iter,
151                                             int flags, struct trace_event *event)
152 {
153         struct trace_branch *field;
154 
155         trace_assign_type(field, iter->ent);
156 
157         if (trace_seq_printf(&iter->seq, "[%s] %s:%s:%d\n",
158                              field->correct ? "  ok  " : " MISS ",
159                              field->func,
160                              field->file,
161                              field->line))
162                 return TRACE_TYPE_PARTIAL_LINE;
163 
164         return TRACE_TYPE_HANDLED;
165 }
166 
167 static void branch_print_header(struct seq_file *s)
168 {
169         seq_puts(s, "#           TASK-PID    CPU#    TIMESTAMP  CORRECT"
170                 "  FUNC:FILE:LINE\n");
171         seq_puts(s, "#              | |       |          |         |   "
172                 "    |\n");
173 }
174 
175 static struct trace_event_functions trace_branch_funcs = {
176         .trace          = trace_branch_print,
177 };
178 
179 static struct trace_event trace_branch_event = {
180         .type           = TRACE_BRANCH,
181         .funcs          = &trace_branch_funcs,
182 };
183 
184 static struct tracer branch_trace __read_mostly =
185 {
186         .name           = "branch",
187         .init           = branch_trace_init,
188         .reset          = branch_trace_reset,
189 #ifdef CONFIG_FTRACE_SELFTEST
190         .selftest       = trace_selftest_startup_branch,
191 #endif /* CONFIG_FTRACE_SELFTEST */
192         .print_header   = branch_print_header,
193 };
194 
195 __init static int init_branch_tracer(void)
196 {
197         int ret;
198 
199         ret = register_ftrace_event(&trace_branch_event);
200         if (!ret) {
201                 printk(KERN_WARNING "Warning: could not register "
202                                     "branch events\n");
203                 return 1;
204         }
205         return register_tracer(&branch_trace);
206 }
207 core_initcall(init_branch_tracer);
208 
209 #else
210 static inline
211 void trace_likely_condition(struct ftrace_branch_data *f, int val, int expect)
212 {
213 }
214 #endif /* CONFIG_BRANCH_TRACER */
215 
216 void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect)
217 {
218         /*
219          * I would love to have a trace point here instead, but the
220          * trace point code is so inundated with unlikely and likely
221          * conditions that the recursive nightmare that exists is too
222          * much to try to get working. At least for now.
223          */
224         trace_likely_condition(f, val, expect);
225 
226         /* FIXME: Make this atomic! */
227         if (val == expect)
228                 f->correct++;
229         else
230                 f->incorrect++;
231 }
232 EXPORT_SYMBOL(ftrace_likely_update);
233 
234 extern unsigned long __start_annotated_branch_profile[];
235 extern unsigned long __stop_annotated_branch_profile[];
236 
237 static int annotated_branch_stat_headers(struct seq_file *m)
238 {
239         seq_printf(m, " correct incorrect  %% ");
240         seq_printf(m, "       Function                "
241                               "  File              Line\n"
242                               " ------- ---------  - "
243                               "       --------                "
244                               "  ----              ----\n");
245         return 0;
246 }
247 
248 static inline long get_incorrect_percent(struct ftrace_branch_data *p)
249 {
250         long percent;
251 
252         if (p->correct) {
253                 percent = p->incorrect * 100;
254                 percent /= p->correct + p->incorrect;
255         } else
256                 percent = p->incorrect ? 100 : -1;
257 
258         return percent;
259 }
260 
261 static int branch_stat_show(struct seq_file *m, void *v)
262 {
263         struct ftrace_branch_data *p = v;
264         const char *f;
265         long percent;
266 
267         /* Only print the file, not the path */
268         f = p->file + strlen(p->file);
269         while (f >= p->file && *f != '/')
270                 f--;
271         f++;
272 
273         /*
274          * The miss is overlayed on correct, and hit on incorrect.
275          */
276         percent = get_incorrect_percent(p);
277 
278         seq_printf(m, "%8lu %8lu ",  p->correct, p->incorrect);
279         if (percent < 0)
280                 seq_printf(m, "  X ");
281         else
282                 seq_printf(m, "%3ld ", percent);
283         seq_printf(m, "%-30.30s %-20.20s %d\n", p->func, f, p->line);
284         return 0;
285 }
286 
287 static void *annotated_branch_stat_start(struct tracer_stat *trace)
288 {
289         return __start_annotated_branch_profile;
290 }
291 
292 static void *
293 annotated_branch_stat_next(void *v, int idx)
294 {
295         struct ftrace_branch_data *p = v;
296 
297         ++p;
298 
299         if ((void *)p >= (void *)__stop_annotated_branch_profile)
300                 return NULL;
301 
302         return p;
303 }
304 
305 static int annotated_branch_stat_cmp(void *p1, void *p2)
306 {
307         struct ftrace_branch_data *a = p1;
308         struct ftrace_branch_data *b = p2;
309 
310         long percent_a, percent_b;
311 
312         percent_a = get_incorrect_percent(a);
313         percent_b = get_incorrect_percent(b);
314 
315         if (percent_a < percent_b)
316                 return -1;
317         if (percent_a > percent_b)
318                 return 1;
319 
320         if (a->incorrect < b->incorrect)
321                 return -1;
322         if (a->incorrect > b->incorrect)
323                 return 1;
324 
325         /*
326          * Since the above shows worse (incorrect) cases
327          * first, we continue that by showing best (correct)
328          * cases last.
329          */
330         if (a->correct > b->correct)
331                 return -1;
332         if (a->correct < b->correct)
333                 return 1;
334 
335         return 0;
336 }
337 
338 static struct tracer_stat annotated_branch_stats = {
339         .name = "branch_annotated",
340         .stat_start = annotated_branch_stat_start,
341         .stat_next = annotated_branch_stat_next,
342         .stat_cmp = annotated_branch_stat_cmp,
343         .stat_headers = annotated_branch_stat_headers,
344         .stat_show = branch_stat_show
345 };
346 
347 __init static int init_annotated_branch_stats(void)
348 {
349         int ret;
350 
351         ret = register_stat_tracer(&annotated_branch_stats);
352         if (!ret) {
353                 printk(KERN_WARNING "Warning: could not register "
354                                     "annotated branches stats\n");
355                 return 1;
356         }
357         return 0;
358 }
359 fs_initcall(init_annotated_branch_stats);
360 
361 #ifdef CONFIG_PROFILE_ALL_BRANCHES
362 
363 extern unsigned long __start_branch_profile[];
364 extern unsigned long __stop_branch_profile[];
365 
366 static int all_branch_stat_headers(struct seq_file *m)
367 {
368         seq_printf(m, "   miss      hit    %% ");
369         seq_printf(m, "       Function                "
370                               "  File              Line\n"
371                               " ------- ---------  - "
372                               "       --------                "
373                               "  ----              ----\n");
374         return 0;
375 }
376 
377 static void *all_branch_stat_start(struct tracer_stat *trace)
378 {
379         return __start_branch_profile;
380 }
381 
382 static void *
383 all_branch_stat_next(void *v, int idx)
384 {
385         struct ftrace_branch_data *p = v;
386 
387         ++p;
388 
389         if ((void *)p >= (void *)__stop_branch_profile)
390                 return NULL;
391 
392         return p;
393 }
394 
395 static struct tracer_stat all_branch_stats = {
396         .name = "branch_all",
397         .stat_start = all_branch_stat_start,
398         .stat_next = all_branch_stat_next,
399         .stat_headers = all_branch_stat_headers,
400         .stat_show = branch_stat_show
401 };
402 
403 __init static int all_annotated_branch_stats(void)
404 {
405         int ret;
406 
407         ret = register_stat_tracer(&all_branch_stats);
408         if (!ret) {
409                 printk(KERN_WARNING "Warning: could not register "
410                                     "all branches stats\n");
411                 return 1;
412         }
413         return 0;
414 }
415 fs_initcall(all_annotated_branch_stats);
416 #endif /* CONFIG_PROFILE_ALL_BRANCHES */
417 

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