4 * @remark Copyright 2002-2009 OProfile authors
5 * @remark Read the file COPYING
7 * @author John Levon <levon@movementarian.org>
8 * @author Barry Kasindorf <barry.kasindorf@amd.com>
9 * @author Robert Richter <robert.richter@amd.com>
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().
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.
22 #include <linux/sched.h>
23 #include <linux/oprofile.h>
24 #include <linux/vmalloc.h>
25 #include <linux/errno.h>
27 #include "event_buffer.h"
28 #include "cpu_buffer.h"
29 #include "buffer_sync.h"
32 #define OP_BUFFER_FLAGS 0
35 * Read and write access is using spin locking. Thus, writing to the
36 * buffer by NMI handler (x86) could occur also during critical
37 * sections when reading the buffer. To avoid this, there are 2
38 * buffers for independent read and write access. Read access is in
39 * process context only, write access only in the NMI handler. If the
40 * read buffer runs empty, both buffers are swapped atomically. There
41 * is potentially a small window during swapping where the buffers are
42 * disabled and samples could be lost.
44 * Using 2 buffers is a little bit overhead, but the solution is clear
45 * and does not require changes in the ring buffer implementation. It
46 * can be changed to a single buffer solution when the ring buffer
47 * access is implemented as non-locking atomic code.
49 static struct ring_buffer
*op_ring_buffer_read
;
50 static struct ring_buffer
*op_ring_buffer_write
;
51 DEFINE_PER_CPU(struct oprofile_cpu_buffer
, cpu_buffer
);
53 static void wq_sync_buffer(struct work_struct
*work
);
55 #define DEFAULT_TIMER_EXPIRE (HZ / 10)
56 static int work_enabled
;
58 unsigned long oprofile_get_cpu_buffer_size(void)
60 return oprofile_cpu_buffer_size
;
63 void oprofile_cpu_buffer_inc_smpl_lost(void)
65 struct oprofile_cpu_buffer
*cpu_buf
66 = &__get_cpu_var(cpu_buffer
);
68 cpu_buf
->sample_lost_overflow
++;
71 void free_cpu_buffers(void)
73 if (op_ring_buffer_read
)
74 ring_buffer_free(op_ring_buffer_read
);
75 op_ring_buffer_read
= NULL
;
76 if (op_ring_buffer_write
)
77 ring_buffer_free(op_ring_buffer_write
);
78 op_ring_buffer_write
= NULL
;
81 int alloc_cpu_buffers(void)
85 unsigned long buffer_size
= oprofile_cpu_buffer_size
;
87 op_ring_buffer_read
= ring_buffer_alloc(buffer_size
, OP_BUFFER_FLAGS
);
88 if (!op_ring_buffer_read
)
90 op_ring_buffer_write
= ring_buffer_alloc(buffer_size
, OP_BUFFER_FLAGS
);
91 if (!op_ring_buffer_write
)
94 for_each_possible_cpu(i
) {
95 struct oprofile_cpu_buffer
*b
= &per_cpu(cpu_buffer
, i
);
98 b
->last_is_kernel
= -1;
100 b
->buffer_size
= buffer_size
;
101 b
->sample_received
= 0;
102 b
->sample_lost_overflow
= 0;
103 b
->backtrace_aborted
= 0;
104 b
->sample_invalid_eip
= 0;
106 INIT_DELAYED_WORK(&b
->work
, wq_sync_buffer
);
115 void start_cpu_work(void)
121 for_each_online_cpu(i
) {
122 struct oprofile_cpu_buffer
*b
= &per_cpu(cpu_buffer
, i
);
125 * Spread the work by 1 jiffy per cpu so they dont all
128 schedule_delayed_work_on(i
, &b
->work
, DEFAULT_TIMER_EXPIRE
+ i
);
132 void end_cpu_work(void)
138 for_each_online_cpu(i
) {
139 struct oprofile_cpu_buffer
*b
= &per_cpu(cpu_buffer
, i
);
141 cancel_delayed_work(&b
->work
);
144 flush_scheduled_work();
148 * This function prepares the cpu buffer to write a sample.
150 * Struct op_entry is used during operations on the ring buffer while
151 * struct op_sample contains the data that is stored in the ring
152 * buffer. Struct entry can be uninitialized. The function reserves a
153 * data array that is specified by size. Use
154 * op_cpu_buffer_write_commit() after preparing the sample. In case of
155 * errors a null pointer is returned, otherwise the pointer to the
160 *op_cpu_buffer_write_reserve(struct op_entry
*entry
, unsigned long size
)
162 entry
->event
= ring_buffer_lock_reserve
163 (op_ring_buffer_write
, sizeof(struct op_sample
) +
164 size
* sizeof(entry
->sample
->data
[0]), &entry
->irq_flags
);
166 entry
->sample
= ring_buffer_event_data(entry
->event
);
168 entry
->sample
= NULL
;
174 entry
->data
= entry
->sample
->data
;
176 return entry
->sample
;
179 int op_cpu_buffer_write_commit(struct op_entry
*entry
)
181 return ring_buffer_unlock_commit(op_ring_buffer_write
, entry
->event
,
185 struct op_sample
*op_cpu_buffer_read_entry(struct op_entry
*entry
, int cpu
)
187 struct ring_buffer_event
*e
;
188 e
= ring_buffer_consume(op_ring_buffer_read
, cpu
, NULL
);
191 if (ring_buffer_swap_cpu(op_ring_buffer_read
,
192 op_ring_buffer_write
,
195 e
= ring_buffer_consume(op_ring_buffer_read
, cpu
, NULL
);
202 entry
->sample
= ring_buffer_event_data(e
);
203 entry
->size
= (ring_buffer_event_length(e
) - sizeof(struct op_sample
))
204 / sizeof(entry
->sample
->data
[0]);
205 entry
->data
= entry
->sample
->data
;
206 return entry
->sample
;
209 unsigned long op_cpu_buffer_entries(int cpu
)
211 return ring_buffer_entries_cpu(op_ring_buffer_read
, cpu
)
212 + ring_buffer_entries_cpu(op_ring_buffer_write
, cpu
);
216 op_add_code(struct oprofile_cpu_buffer
*cpu_buf
, unsigned long backtrace
,
217 int is_kernel
, struct task_struct
*task
)
219 struct op_entry entry
;
220 struct op_sample
*sample
;
227 flags
|= TRACE_BEGIN
;
229 /* notice a switch from user->kernel or vice versa */
230 is_kernel
= !!is_kernel
;
231 if (cpu_buf
->last_is_kernel
!= is_kernel
) {
232 cpu_buf
->last_is_kernel
= is_kernel
;
233 flags
|= KERNEL_CTX_SWITCH
;
238 /* notice a task switch */
239 if (cpu_buf
->last_task
!= task
) {
240 cpu_buf
->last_task
= task
;
241 flags
|= USER_CTX_SWITCH
;
248 if (flags
& USER_CTX_SWITCH
)
253 sample
= op_cpu_buffer_write_reserve(&entry
, size
);
257 sample
->eip
= ESCAPE_CODE
;
258 sample
->event
= flags
;
261 op_cpu_buffer_add_data(&entry
, (unsigned long)task
);
263 op_cpu_buffer_write_commit(&entry
);
269 op_add_sample(struct oprofile_cpu_buffer
*cpu_buf
,
270 unsigned long pc
, unsigned long event
)
272 struct op_entry entry
;
273 struct op_sample
*sample
;
275 sample
= op_cpu_buffer_write_reserve(&entry
, 0);
280 sample
->event
= event
;
282 return op_cpu_buffer_write_commit(&entry
);
286 * This must be safe from any context.
288 * is_kernel is needed because on some architectures you cannot
289 * tell if you are in kernel or user space simply by looking at
290 * pc. We tag this in the buffer by generating kernel enter/exit
291 * events whenever is_kernel changes
294 log_sample(struct oprofile_cpu_buffer
*cpu_buf
, unsigned long pc
,
295 unsigned long backtrace
, int is_kernel
, unsigned long event
)
297 cpu_buf
->sample_received
++;
299 if (pc
== ESCAPE_CODE
) {
300 cpu_buf
->sample_invalid_eip
++;
304 if (op_add_code(cpu_buf
, backtrace
, is_kernel
, current
))
307 if (op_add_sample(cpu_buf
, pc
, event
))
313 cpu_buf
->sample_lost_overflow
++;
317 static inline void oprofile_begin_trace(struct oprofile_cpu_buffer
*cpu_buf
)
319 cpu_buf
->tracing
= 1;
322 static inline void oprofile_end_trace(struct oprofile_cpu_buffer
*cpu_buf
)
324 cpu_buf
->tracing
= 0;
328 __oprofile_add_ext_sample(unsigned long pc
, struct pt_regs
* const regs
,
329 unsigned long event
, int is_kernel
)
331 struct oprofile_cpu_buffer
*cpu_buf
= &__get_cpu_var(cpu_buffer
);
332 unsigned long backtrace
= oprofile_backtrace_depth
;
335 * if log_sample() fail we can't backtrace since we lost the
336 * source of this event
338 if (!log_sample(cpu_buf
, pc
, backtrace
, is_kernel
, event
))
345 oprofile_begin_trace(cpu_buf
);
346 oprofile_ops
.backtrace(regs
, backtrace
);
347 oprofile_end_trace(cpu_buf
);
350 void oprofile_add_ext_sample(unsigned long pc
, struct pt_regs
* const regs
,
351 unsigned long event
, int is_kernel
)
353 __oprofile_add_ext_sample(pc
, regs
, event
, is_kernel
);
356 void oprofile_add_sample(struct pt_regs
* const regs
, unsigned long event
)
358 int is_kernel
= !user_mode(regs
);
359 unsigned long pc
= profile_pc(regs
);
361 __oprofile_add_ext_sample(pc
, regs
, event
, is_kernel
);
364 #ifdef CONFIG_OPROFILE_IBS
366 void oprofile_add_ibs_sample(struct pt_regs
* const regs
,
367 unsigned int * const ibs_sample
, int ibs_code
)
369 int is_kernel
= !user_mode(regs
);
370 struct oprofile_cpu_buffer
*cpu_buf
= &__get_cpu_var(cpu_buffer
);
373 cpu_buf
->sample_received
++;
375 /* backtraces disabled for ibs */
376 fail
= fail
|| op_add_code(cpu_buf
, 0, is_kernel
, current
);
378 fail
= fail
|| op_add_sample(cpu_buf
, ESCAPE_CODE
, ibs_code
);
379 fail
= fail
|| op_add_sample(cpu_buf
, ibs_sample
[0], ibs_sample
[1]);
380 fail
= fail
|| op_add_sample(cpu_buf
, ibs_sample
[2], ibs_sample
[3]);
381 fail
= fail
|| op_add_sample(cpu_buf
, ibs_sample
[4], ibs_sample
[5]);
383 if (ibs_code
== IBS_OP_BEGIN
) {
384 fail
= fail
|| op_add_sample(cpu_buf
, ibs_sample
[6], ibs_sample
[7]);
385 fail
= fail
|| op_add_sample(cpu_buf
, ibs_sample
[8], ibs_sample
[9]);
386 fail
= fail
|| op_add_sample(cpu_buf
, ibs_sample
[10], ibs_sample
[11]);
390 cpu_buf
->sample_lost_overflow
++;
395 void oprofile_add_pc(unsigned long pc
, int is_kernel
, unsigned long event
)
397 struct oprofile_cpu_buffer
*cpu_buf
= &__get_cpu_var(cpu_buffer
);
398 log_sample(cpu_buf
, pc
, 0, is_kernel
, event
);
401 void oprofile_add_trace(unsigned long pc
)
403 struct oprofile_cpu_buffer
*cpu_buf
= &__get_cpu_var(cpu_buffer
);
405 if (!cpu_buf
->tracing
)
409 * broken frame can give an eip with the same value as an
410 * escape code, abort the trace if we get it
412 if (pc
== ESCAPE_CODE
)
415 if (op_add_sample(cpu_buf
, pc
, 0))
420 cpu_buf
->tracing
= 0;
421 cpu_buf
->backtrace_aborted
++;
426 * This serves to avoid cpu buffer overflow, and makes sure
427 * the task mortuary progresses
429 * By using schedule_delayed_work_on and then schedule_delayed_work
430 * we guarantee this will stay on the correct cpu
432 static void wq_sync_buffer(struct work_struct
*work
)
434 struct oprofile_cpu_buffer
*b
=
435 container_of(work
, struct oprofile_cpu_buffer
, work
.work
);
436 if (b
->cpu
!= smp_processor_id()) {
437 printk(KERN_DEBUG
"WQ on CPU%d, prefer CPU%d\n",
438 smp_processor_id(), b
->cpu
);
440 if (!cpu_online(b
->cpu
)) {
441 cancel_delayed_work(&b
->work
);
447 /* don't re-add the work if we're shutting down */
449 schedule_delayed_work(&b
->work
, DEFAULT_TIMER_EXPIRE
);
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