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

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