oprofile: Adding switch counter to oprofile statistic variables
[linux-2.6.git] / drivers / oprofile / cpu_buffer.c
1 /**
2  * @file cpu_buffer.c
3  *
4  * @remark Copyright 2002-2009 OProfile authors
5  * @remark Read the file COPYING
6  *
7  * @author John Levon <levon@movementarian.org>
8  * @author Barry Kasindorf <barry.kasindorf@amd.com>
9  * @author Robert Richter <robert.richter@amd.com>
10  *
11  * Each CPU has a local buffer that stores PC value/event
12  * pairs. We also log context switches when we notice them.
13  * Eventually each CPU's buffer is processed into the global
14  * event buffer by sync_buffer().
15  *
16  * We use a local buffer for two reasons: an NMI or similar
17  * interrupt cannot synchronise, and high sampling rates
18  * would lead to catastrophic global synchronisation if
19  * a global buffer was used.
20  */
21
22 #include <linux/sched.h>
23 #include <linux/oprofile.h>
24 #include <linux/errno.h>
25
26 #include "event_buffer.h"
27 #include "cpu_buffer.h"
28 #include "buffer_sync.h"
29 #include "oprof.h"
30
31 #define OP_BUFFER_FLAGS 0
32
33 /*
34  * Read and write access is using spin locking. Thus, writing to the
35  * buffer by NMI handler (x86) could occur also during critical
36  * sections when reading the buffer. To avoid this, there are 2
37  * buffers for independent read and write access. Read access is in
38  * process context only, write access only in the NMI handler. If the
39  * read buffer runs empty, both buffers are swapped atomically. There
40  * is potentially a small window during swapping where the buffers are
41  * disabled and samples could be lost.
42  *
43  * Using 2 buffers is a little bit overhead, but the solution is clear
44  * and does not require changes in the ring buffer implementation. It
45  * can be changed to a single buffer solution when the ring buffer
46  * access is implemented as non-locking atomic code.
47  */
48 static struct ring_buffer *op_ring_buffer_read;
49 static struct ring_buffer *op_ring_buffer_write;
50 DEFINE_PER_CPU(struct oprofile_cpu_buffer, cpu_buffer);
51
52 static void wq_sync_buffer(struct work_struct *work);
53
54 #define DEFAULT_TIMER_EXPIRE (HZ / 10)
55 static int work_enabled;
56
57 unsigned long oprofile_get_cpu_buffer_size(void)
58 {
59         return oprofile_cpu_buffer_size;
60 }
61
62 void oprofile_cpu_buffer_inc_smpl_lost(void)
63 {
64         struct oprofile_cpu_buffer *cpu_buf
65                 = &__get_cpu_var(cpu_buffer);
66
67         cpu_buf->sample_lost_overflow++;
68 }
69
70 void free_cpu_buffers(void)
71 {
72         if (op_ring_buffer_read)
73                 ring_buffer_free(op_ring_buffer_read);
74         op_ring_buffer_read = NULL;
75         if (op_ring_buffer_write)
76                 ring_buffer_free(op_ring_buffer_write);
77         op_ring_buffer_write = NULL;
78 }
79
80 #define RB_EVENT_HDR_SIZE 4
81
82 int alloc_cpu_buffers(void)
83 {
84         int i;
85
86         unsigned long buffer_size = oprofile_cpu_buffer_size;
87         unsigned long byte_size = buffer_size * (sizeof(struct op_sample) +
88                                                  RB_EVENT_HDR_SIZE);
89
90         op_ring_buffer_read = ring_buffer_alloc(byte_size, OP_BUFFER_FLAGS);
91         if (!op_ring_buffer_read)
92                 goto fail;
93         op_ring_buffer_write = ring_buffer_alloc(byte_size, OP_BUFFER_FLAGS);
94         if (!op_ring_buffer_write)
95                 goto fail;
96
97         for_each_possible_cpu(i) {
98                 struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
99
100                 b->last_task = NULL;
101                 b->last_is_kernel = -1;
102                 b->tracing = 0;
103                 b->buffer_size = buffer_size;
104                 b->sample_received = 0;
105                 b->sample_lost_overflow = 0;
106                 b->backtrace_aborted = 0;
107                 b->sample_invalid_eip = 0;
108                 b->cpu = i;
109                 INIT_DELAYED_WORK(&b->work, wq_sync_buffer);
110         }
111         return 0;
112
113 fail:
114         free_cpu_buffers();
115         return -ENOMEM;
116 }
117
118 void start_cpu_work(void)
119 {
120         int i;
121
122         work_enabled = 1;
123
124         for_each_online_cpu(i) {
125                 struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
126
127                 /*
128                  * Spread the work by 1 jiffy per cpu so they dont all
129                  * fire at once.
130                  */
131                 schedule_delayed_work_on(i, &b->work, DEFAULT_TIMER_EXPIRE + i);
132         }
133 }
134
135 void end_cpu_work(void)
136 {
137         int i;
138
139         work_enabled = 0;
140
141         for_each_online_cpu(i) {
142                 struct oprofile_cpu_buffer *b = &per_cpu(cpu_buffer, i);
143
144                 cancel_delayed_work(&b->work);
145         }
146
147         flush_scheduled_work();
148 }
149
150 /*
151  * This function prepares the cpu buffer to write a sample.
152  *
153  * Struct op_entry is used during operations on the ring buffer while
154  * struct op_sample contains the data that is stored in the ring
155  * buffer. Struct entry can be uninitialized. The function reserves a
156  * data array that is specified by size. Use
157  * op_cpu_buffer_write_commit() after preparing the sample. In case of
158  * errors a null pointer is returned, otherwise the pointer to the
159  * sample.
160  *
161  */
162 struct op_sample
163 *op_cpu_buffer_write_reserve(struct op_entry *entry, unsigned long size)
164 {
165         entry->event = ring_buffer_lock_reserve
166                 (op_ring_buffer_write, sizeof(struct op_sample) +
167                  size * sizeof(entry->sample->data[0]));
168         if (entry->event)
169                 entry->sample = ring_buffer_event_data(entry->event);
170         else
171                 entry->sample = NULL;
172
173         if (!entry->sample)
174                 return NULL;
175
176         entry->size = size;
177         entry->data = entry->sample->data;
178
179         return entry->sample;
180 }
181
182 int op_cpu_buffer_write_commit(struct op_entry *entry)
183 {
184         return ring_buffer_unlock_commit(op_ring_buffer_write, entry->event);
185 }
186
187 struct op_sample *op_cpu_buffer_read_entry(struct op_entry *entry, int cpu)
188 {
189         struct ring_buffer_event *e;
190         e = ring_buffer_consume(op_ring_buffer_read, cpu, NULL);
191         if (e)
192                 goto event;
193         if (ring_buffer_swap_cpu(op_ring_buffer_read,
194                                  op_ring_buffer_write,
195                                  cpu))
196                 return NULL;
197         e = ring_buffer_consume(op_ring_buffer_read, cpu, NULL);
198         if (e)
199                 goto event;
200         return NULL;
201
202 event:
203         entry->event = e;
204         entry->sample = ring_buffer_event_data(e);
205         entry->size = (ring_buffer_event_length(e) - sizeof(struct op_sample))
206                 / sizeof(entry->sample->data[0]);
207         entry->data = entry->sample->data;
208         return entry->sample;
209 }
210
211 unsigned long op_cpu_buffer_entries(int cpu)
212 {
213         return ring_buffer_entries_cpu(op_ring_buffer_read, cpu)
214                 + ring_buffer_entries_cpu(op_ring_buffer_write, cpu);
215 }
216
217 static int
218 op_add_code(struct oprofile_cpu_buffer *cpu_buf, unsigned long backtrace,
219             int is_kernel, struct task_struct *task)
220 {
221         struct op_entry entry;
222         struct op_sample *sample;
223         unsigned long flags;
224         int size;
225
226         flags = 0;
227
228         if (backtrace)
229                 flags |= TRACE_BEGIN;
230
231         /* notice a switch from user->kernel or vice versa */
232         is_kernel = !!is_kernel;
233         if (cpu_buf->last_is_kernel != is_kernel) {
234                 cpu_buf->last_is_kernel = is_kernel;
235                 flags |= KERNEL_CTX_SWITCH;
236                 if (is_kernel)
237                         flags |= IS_KERNEL;
238         }
239
240         /* notice a task switch */
241         if (cpu_buf->last_task != task) {
242                 cpu_buf->last_task = task;
243                 flags |= USER_CTX_SWITCH;
244         }
245
246         if (!flags)
247                 /* nothing to do */
248                 return 0;
249
250         if (flags & USER_CTX_SWITCH)
251                 size = 1;
252         else
253                 size = 0;
254
255         sample = op_cpu_buffer_write_reserve(&entry, size);
256         if (!sample)
257                 return -ENOMEM;
258
259         sample->eip = ESCAPE_CODE;
260         sample->event = flags;
261
262         if (size)
263                 op_cpu_buffer_add_data(&entry, (unsigned long)task);
264
265         op_cpu_buffer_write_commit(&entry);
266
267         return 0;
268 }
269
270 static inline int
271 op_add_sample(struct oprofile_cpu_buffer *cpu_buf,
272               unsigned long pc, unsigned long event)
273 {
274         struct op_entry entry;
275         struct op_sample *sample;
276
277         sample = op_cpu_buffer_write_reserve(&entry, 0);
278         if (!sample)
279                 return -ENOMEM;
280
281         sample->eip = pc;
282         sample->event = event;
283
284         return op_cpu_buffer_write_commit(&entry);
285 }
286
287 /*
288  * This must be safe from any context.
289  *
290  * is_kernel is needed because on some architectures you cannot
291  * tell if you are in kernel or user space simply by looking at
292  * pc. We tag this in the buffer by generating kernel enter/exit
293  * events whenever is_kernel changes
294  */
295 static int
296 log_sample(struct oprofile_cpu_buffer *cpu_buf, unsigned long pc,
297            unsigned long backtrace, int is_kernel, unsigned long event)
298 {
299         cpu_buf->sample_received++;
300
301         if (pc == ESCAPE_CODE) {
302                 cpu_buf->sample_invalid_eip++;
303                 return 0;
304         }
305
306         if (op_add_code(cpu_buf, backtrace, is_kernel, current))
307                 goto fail;
308
309         if (op_add_sample(cpu_buf, pc, event))
310                 goto fail;
311
312         return 1;
313
314 fail:
315         cpu_buf->sample_lost_overflow++;
316         return 0;
317 }
318
319 static inline void oprofile_begin_trace(struct oprofile_cpu_buffer *cpu_buf)
320 {
321         cpu_buf->tracing = 1;
322 }
323
324 static inline void oprofile_end_trace(struct oprofile_cpu_buffer *cpu_buf)
325 {
326         cpu_buf->tracing = 0;
327 }
328
329 static inline void
330 __oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs,
331                           unsigned long event, int is_kernel)
332 {
333         struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
334         unsigned long backtrace = oprofile_backtrace_depth;
335
336         /*
337          * if log_sample() fail we can't backtrace since we lost the
338          * source of this event
339          */
340         if (!log_sample(cpu_buf, pc, backtrace, is_kernel, event))
341                 /* failed */
342                 return;
343
344         if (!backtrace)
345                 return;
346
347         oprofile_begin_trace(cpu_buf);
348         oprofile_ops.backtrace(regs, backtrace);
349         oprofile_end_trace(cpu_buf);
350 }
351
352 void oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs,
353                              unsigned long event, int is_kernel)
354 {
355         __oprofile_add_ext_sample(pc, regs, event, is_kernel);
356 }
357
358 void oprofile_add_sample(struct pt_regs * const regs, unsigned long event)
359 {
360         int is_kernel = !user_mode(regs);
361         unsigned long pc = profile_pc(regs);
362
363         __oprofile_add_ext_sample(pc, regs, event, is_kernel);
364 }
365
366 /*
367  * Add samples with data to the ring buffer.
368  *
369  * Use oprofile_add_data(&entry, val) to add data and
370  * oprofile_write_commit(&entry) to commit the sample.
371  */
372 void
373 oprofile_write_reserve(struct op_entry *entry, struct pt_regs * const regs,
374                        unsigned long pc, int code, int size)
375 {
376         struct op_sample *sample;
377         int is_kernel = !user_mode(regs);
378         struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
379
380         cpu_buf->sample_received++;
381
382         /* no backtraces for samples with data */
383         if (op_add_code(cpu_buf, 0, is_kernel, current))
384                 goto fail;
385
386         sample = op_cpu_buffer_write_reserve(entry, size + 2);
387         if (!sample)
388                 goto fail;
389         sample->eip = ESCAPE_CODE;
390         sample->event = 0;              /* no flags */
391
392         op_cpu_buffer_add_data(entry, code);
393         op_cpu_buffer_add_data(entry, pc);
394
395         return;
396
397 fail:
398         entry->event = NULL;
399         cpu_buf->sample_lost_overflow++;
400 }
401
402 int oprofile_add_data(struct op_entry *entry, unsigned long val)
403 {
404         if (!entry->event)
405                 return 0;
406         return op_cpu_buffer_add_data(entry, val);
407 }
408
409 int oprofile_add_data64(struct op_entry *entry, u64 val)
410 {
411         if (!entry->event)
412                 return 0;
413         if (op_cpu_buffer_get_size(entry) < 2)
414                 /*
415                  * the function returns 0 to indicate a too small
416                  * buffer, even if there is some space left
417                  */
418                 return 0;
419         if (!op_cpu_buffer_add_data(entry, (u32)val))
420                 return 0;
421         return op_cpu_buffer_add_data(entry, (u32)(val >> 32));
422 }
423
424 int oprofile_write_commit(struct op_entry *entry)
425 {
426         if (!entry->event)
427                 return -EINVAL;
428         return op_cpu_buffer_write_commit(entry);
429 }
430
431 void oprofile_add_pc(unsigned long pc, int is_kernel, unsigned long event)
432 {
433         struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
434         log_sample(cpu_buf, pc, 0, is_kernel, event);
435 }
436
437 void oprofile_add_trace(unsigned long pc)
438 {
439         struct oprofile_cpu_buffer *cpu_buf = &__get_cpu_var(cpu_buffer);
440
441         if (!cpu_buf->tracing)
442                 return;
443
444         /*
445          * broken frame can give an eip with the same value as an
446          * escape code, abort the trace if we get it
447          */
448         if (pc == ESCAPE_CODE)
449                 goto fail;
450
451         if (op_add_sample(cpu_buf, pc, 0))
452                 goto fail;
453
454         return;
455 fail:
456         cpu_buf->tracing = 0;
457         cpu_buf->backtrace_aborted++;
458         return;
459 }
460
461 /*
462  * This serves to avoid cpu buffer overflow, and makes sure
463  * the task mortuary progresses
464  *
465  * By using schedule_delayed_work_on and then schedule_delayed_work
466  * we guarantee this will stay on the correct cpu
467  */
468 static void wq_sync_buffer(struct work_struct *work)
469 {
470         struct oprofile_cpu_buffer *b =
471                 container_of(work, struct oprofile_cpu_buffer, work.work);
472         if (b->cpu != smp_processor_id()) {
473                 printk(KERN_DEBUG "WQ on CPU%d, prefer CPU%d\n",
474                        smp_processor_id(), b->cpu);
475
476                 if (!cpu_online(b->cpu)) {
477                         cancel_delayed_work(&b->work);
478                         return;
479                 }
480         }
481         sync_buffer(b->cpu);
482
483         /* don't re-add the work if we're shutting down */
484         if (work_enabled)
485                 schedule_delayed_work(&b->work, DEFAULT_TIMER_EXPIRE);
486 }