blob: 026f671ea55870bcecfe82e510004d33967eb5ad [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/**
2 * @file cpu_buffer.c
3 *
4 * @remark Copyright 2002 OProfile authors
5 * @remark Read the file COPYING
6 *
7 * @author John Levon <levon@movementarian.org>
8 *
9 * Each CPU has a local buffer that stores PC value/event
10 * pairs. We also log context switches when we notice them.
11 * Eventually each CPU's buffer is processed into the global
12 * event buffer by sync_buffer().
13 *
14 * We use a local buffer for two reasons: an NMI or similar
15 * interrupt cannot synchronise, and high sampling rates
16 * would lead to catastrophic global synchronisation if
17 * a global buffer was used.
18 */
19
20#include <linux/sched.h>
21#include <linux/oprofile.h>
22#include <linux/vmalloc.h>
23#include <linux/errno.h>
24
25#include "event_buffer.h"
26#include "cpu_buffer.h"
27#include "buffer_sync.h"
28#include "oprof.h"
29
30struct oprofile_cpu_buffer cpu_buffer[NR_CPUS] __cacheline_aligned;
31
32static void wq_sync_buffer(void *);
33
34#define DEFAULT_TIMER_EXPIRE (HZ / 10)
35static int work_enabled;
36
37void free_cpu_buffers(void)
38{
39 int i;
40
41 for_each_online_cpu(i) {
42 vfree(cpu_buffer[i].buffer);
43 }
44}
Jesper Juhl77933d72005-07-27 11:46:09 -070045
Linus Torvalds1da177e2005-04-16 15:20:36 -070046int alloc_cpu_buffers(void)
47{
48 int i;
49
50 unsigned long buffer_size = fs_cpu_buffer_size;
51
52 for_each_online_cpu(i) {
53 struct oprofile_cpu_buffer * b = &cpu_buffer[i];
54
55 b->buffer = vmalloc(sizeof(struct op_sample) * buffer_size);
56 if (!b->buffer)
57 goto fail;
58
59 b->last_task = NULL;
60 b->last_is_kernel = -1;
61 b->tracing = 0;
62 b->buffer_size = buffer_size;
63 b->tail_pos = 0;
64 b->head_pos = 0;
65 b->sample_received = 0;
66 b->sample_lost_overflow = 0;
67 b->cpu = i;
68 INIT_WORK(&b->work, wq_sync_buffer, b);
69 }
70 return 0;
71
72fail:
73 free_cpu_buffers();
74 return -ENOMEM;
75}
Linus Torvalds1da177e2005-04-16 15:20:36 -070076
77void start_cpu_work(void)
78{
79 int i;
80
81 work_enabled = 1;
82
83 for_each_online_cpu(i) {
84 struct oprofile_cpu_buffer * b = &cpu_buffer[i];
85
86 /*
87 * Spread the work by 1 jiffy per cpu so they dont all
88 * fire at once.
89 */
90 schedule_delayed_work_on(i, &b->work, DEFAULT_TIMER_EXPIRE + i);
91 }
92}
93
Linus Torvalds1da177e2005-04-16 15:20:36 -070094void end_cpu_work(void)
95{
96 int i;
97
98 work_enabled = 0;
99
100 for_each_online_cpu(i) {
101 struct oprofile_cpu_buffer * b = &cpu_buffer[i];
102
103 cancel_delayed_work(&b->work);
104 }
105
106 flush_scheduled_work();
107}
108
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109/* Resets the cpu buffer to a sane state. */
110void cpu_buffer_reset(struct oprofile_cpu_buffer * cpu_buf)
111{
112 /* reset these to invalid values; the next sample
113 * collected will populate the buffer with proper
114 * values to initialize the buffer
115 */
116 cpu_buf->last_is_kernel = -1;
117 cpu_buf->last_task = NULL;
118}
119
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120/* compute number of available slots in cpu_buffer queue */
121static unsigned long nr_available_slots(struct oprofile_cpu_buffer const * b)
122{
123 unsigned long head = b->head_pos;
124 unsigned long tail = b->tail_pos;
125
126 if (tail > head)
127 return (tail - head) - 1;
128
129 return tail + (b->buffer_size - head) - 1;
130}
131
Linus Torvalds1da177e2005-04-16 15:20:36 -0700132static void increment_head(struct oprofile_cpu_buffer * b)
133{
134 unsigned long new_head = b->head_pos + 1;
135
136 /* Ensure anything written to the slot before we
137 * increment is visible */
138 wmb();
139
140 if (new_head < b->buffer_size)
141 b->head_pos = new_head;
142 else
143 b->head_pos = 0;
144}
145
Jesper Juhl77933d72005-07-27 11:46:09 -0700146static inline void
Linus Torvalds1da177e2005-04-16 15:20:36 -0700147add_sample(struct oprofile_cpu_buffer * cpu_buf,
148 unsigned long pc, unsigned long event)
149{
150 struct op_sample * entry = &cpu_buf->buffer[cpu_buf->head_pos];
151 entry->eip = pc;
152 entry->event = event;
153 increment_head(cpu_buf);
154}
155
Jesper Juhl77933d72005-07-27 11:46:09 -0700156static inline void
Linus Torvalds1da177e2005-04-16 15:20:36 -0700157add_code(struct oprofile_cpu_buffer * buffer, unsigned long value)
158{
159 add_sample(buffer, ESCAPE_CODE, value);
160}
161
Linus Torvalds1da177e2005-04-16 15:20:36 -0700162/* This must be safe from any context. It's safe writing here
163 * because of the head/tail separation of the writer and reader
164 * of the CPU buffer.
165 *
166 * is_kernel is needed because on some architectures you cannot
167 * tell if you are in kernel or user space simply by looking at
168 * pc. We tag this in the buffer by generating kernel enter/exit
169 * events whenever is_kernel changes
170 */
171static int log_sample(struct oprofile_cpu_buffer * cpu_buf, unsigned long pc,
172 int is_kernel, unsigned long event)
173{
174 struct task_struct * task;
175
176 cpu_buf->sample_received++;
177
178 if (nr_available_slots(cpu_buf) < 3) {
179 cpu_buf->sample_lost_overflow++;
180 return 0;
181 }
182
183 is_kernel = !!is_kernel;
184
185 task = current;
186
187 /* notice a switch from user->kernel or vice versa */
188 if (cpu_buf->last_is_kernel != is_kernel) {
189 cpu_buf->last_is_kernel = is_kernel;
190 add_code(cpu_buf, is_kernel);
191 }
192
193 /* notice a task switch */
194 if (cpu_buf->last_task != task) {
195 cpu_buf->last_task = task;
196 add_code(cpu_buf, (unsigned long)task);
197 }
198
199 add_sample(cpu_buf, pc, event);
200 return 1;
201}
202
203static int oprofile_begin_trace(struct oprofile_cpu_buffer * cpu_buf)
204{
205 if (nr_available_slots(cpu_buf) < 4) {
206 cpu_buf->sample_lost_overflow++;
207 return 0;
208 }
209
210 add_code(cpu_buf, CPU_TRACE_BEGIN);
211 cpu_buf->tracing = 1;
212 return 1;
213}
214
Linus Torvalds1da177e2005-04-16 15:20:36 -0700215static void oprofile_end_trace(struct oprofile_cpu_buffer * cpu_buf)
216{
217 cpu_buf->tracing = 0;
218}
219
Linus Torvalds1da177e2005-04-16 15:20:36 -0700220void oprofile_add_sample(struct pt_regs * const regs, unsigned long event)
221{
222 struct oprofile_cpu_buffer * cpu_buf = &cpu_buffer[smp_processor_id()];
223 unsigned long pc = profile_pc(regs);
224 int is_kernel = !user_mode(regs);
225
226 if (!backtrace_depth) {
227 log_sample(cpu_buf, pc, is_kernel, event);
228 return;
229 }
230
231 if (!oprofile_begin_trace(cpu_buf))
232 return;
233
234 /* if log_sample() fail we can't backtrace since we lost the source
235 * of this event */
236 if (log_sample(cpu_buf, pc, is_kernel, event))
237 oprofile_ops.backtrace(regs, backtrace_depth);
238 oprofile_end_trace(cpu_buf);
239}
240
Linus Torvalds1da177e2005-04-16 15:20:36 -0700241void oprofile_add_pc(unsigned long pc, int is_kernel, unsigned long event)
242{
243 struct oprofile_cpu_buffer * cpu_buf = &cpu_buffer[smp_processor_id()];
244 log_sample(cpu_buf, pc, is_kernel, event);
245}
246
Linus Torvalds1da177e2005-04-16 15:20:36 -0700247void oprofile_add_trace(unsigned long pc)
248{
249 struct oprofile_cpu_buffer * cpu_buf = &cpu_buffer[smp_processor_id()];
250
251 if (!cpu_buf->tracing)
252 return;
253
254 if (nr_available_slots(cpu_buf) < 1) {
255 cpu_buf->tracing = 0;
256 cpu_buf->sample_lost_overflow++;
257 return;
258 }
259
260 /* broken frame can give an eip with the same value as an escape code,
261 * abort the trace if we get it */
262 if (pc == ESCAPE_CODE) {
263 cpu_buf->tracing = 0;
264 cpu_buf->backtrace_aborted++;
265 return;
266 }
267
268 add_sample(cpu_buf, pc, 0);
269}
270
Linus Torvalds1da177e2005-04-16 15:20:36 -0700271/*
272 * This serves to avoid cpu buffer overflow, and makes sure
273 * the task mortuary progresses
274 *
275 * By using schedule_delayed_work_on and then schedule_delayed_work
276 * we guarantee this will stay on the correct cpu
277 */
278static void wq_sync_buffer(void * data)
279{
280 struct oprofile_cpu_buffer * b = data;
281 if (b->cpu != smp_processor_id()) {
282 printk("WQ on CPU%d, prefer CPU%d\n",
283 smp_processor_id(), b->cpu);
284 }
285 sync_buffer(b->cpu);
286
287 /* don't re-add the work if we're shutting down */
288 if (work_enabled)
289 schedule_delayed_work(&b->work, DEFAULT_TIMER_EXPIRE);
290}