Commit | Line | Data |
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1da177e4 LT |
1 | /** |
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 | ||
30 | struct oprofile_cpu_buffer cpu_buffer[NR_CPUS] __cacheline_aligned; | |
31 | ||
c4028958 | 32 | static void wq_sync_buffer(struct work_struct *work); |
1da177e4 LT |
33 | |
34 | #define DEFAULT_TIMER_EXPIRE (HZ / 10) | |
35 | static int work_enabled; | |
36 | ||
37 | void free_cpu_buffers(void) | |
38 | { | |
39 | int i; | |
40 | ||
394e3902 | 41 | for_each_online_cpu(i) |
1da177e4 | 42 | vfree(cpu_buffer[i].buffer); |
1da177e4 | 43 | } |
77933d72 | 44 | |
1da177e4 LT |
45 | int alloc_cpu_buffers(void) |
46 | { | |
47 | int i; | |
48 | ||
49 | unsigned long buffer_size = fs_cpu_buffer_size; | |
50 | ||
51 | for_each_online_cpu(i) { | |
52 | struct oprofile_cpu_buffer * b = &cpu_buffer[i]; | |
53 | ||
25ab7cd8 ED |
54 | b->buffer = vmalloc_node(sizeof(struct op_sample) * buffer_size, |
55 | cpu_to_node(i)); | |
1da177e4 LT |
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; | |
c4028958 | 68 | INIT_DELAYED_WORK(&b->work, wq_sync_buffer); |
1da177e4 LT |
69 | } |
70 | return 0; | |
71 | ||
72 | fail: | |
73 | free_cpu_buffers(); | |
74 | return -ENOMEM; | |
75 | } | |
1da177e4 LT |
76 | |
77 | void 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 | ||
1da177e4 LT |
94 | void 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 | ||
1da177e4 LT |
109 | /* Resets the cpu buffer to a sane state. */ |
110 | void 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 | ||
1da177e4 LT |
120 | /* compute number of available slots in cpu_buffer queue */ |
121 | static 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 | ||
1da177e4 LT |
132 | static 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 | ||
77933d72 | 146 | static inline void |
1da177e4 LT |
147 | add_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 | ||
77933d72 | 156 | static inline void |
1da177e4 LT |
157 | add_code(struct oprofile_cpu_buffer * buffer, unsigned long value) |
158 | { | |
159 | add_sample(buffer, ESCAPE_CODE, value); | |
160 | } | |
161 | ||
1da177e4 LT |
162 | /* 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 | */ | |
171 | static 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 | ||
203 | static 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 | ||
1da177e4 LT |
215 | static void oprofile_end_trace(struct oprofile_cpu_buffer * cpu_buf) |
216 | { | |
217 | cpu_buf->tracing = 0; | |
218 | } | |
219 | ||
27357716 BR |
220 | void oprofile_add_ext_sample(unsigned long pc, struct pt_regs * const regs, |
221 | unsigned long event, int is_kernel) | |
1da177e4 LT |
222 | { |
223 | struct oprofile_cpu_buffer * cpu_buf = &cpu_buffer[smp_processor_id()]; | |
1da177e4 LT |
224 | |
225 | if (!backtrace_depth) { | |
226 | log_sample(cpu_buf, pc, is_kernel, event); | |
227 | return; | |
228 | } | |
229 | ||
230 | if (!oprofile_begin_trace(cpu_buf)) | |
231 | return; | |
232 | ||
233 | /* if log_sample() fail we can't backtrace since we lost the source | |
234 | * of this event */ | |
235 | if (log_sample(cpu_buf, pc, is_kernel, event)) | |
236 | oprofile_ops.backtrace(regs, backtrace_depth); | |
237 | oprofile_end_trace(cpu_buf); | |
238 | } | |
239 | ||
27357716 BR |
240 | void oprofile_add_sample(struct pt_regs * const regs, unsigned long event) |
241 | { | |
242 | int is_kernel = !user_mode(regs); | |
243 | unsigned long pc = profile_pc(regs); | |
244 | ||
245 | oprofile_add_ext_sample(pc, regs, event, is_kernel); | |
246 | } | |
247 | ||
1da177e4 LT |
248 | void oprofile_add_pc(unsigned long pc, int is_kernel, unsigned long event) |
249 | { | |
250 | struct oprofile_cpu_buffer * cpu_buf = &cpu_buffer[smp_processor_id()]; | |
251 | log_sample(cpu_buf, pc, is_kernel, event); | |
252 | } | |
253 | ||
1da177e4 LT |
254 | void oprofile_add_trace(unsigned long pc) |
255 | { | |
256 | struct oprofile_cpu_buffer * cpu_buf = &cpu_buffer[smp_processor_id()]; | |
257 | ||
258 | if (!cpu_buf->tracing) | |
259 | return; | |
260 | ||
261 | if (nr_available_slots(cpu_buf) < 1) { | |
262 | cpu_buf->tracing = 0; | |
263 | cpu_buf->sample_lost_overflow++; | |
264 | return; | |
265 | } | |
266 | ||
267 | /* broken frame can give an eip with the same value as an escape code, | |
268 | * abort the trace if we get it */ | |
269 | if (pc == ESCAPE_CODE) { | |
270 | cpu_buf->tracing = 0; | |
271 | cpu_buf->backtrace_aborted++; | |
272 | return; | |
273 | } | |
274 | ||
275 | add_sample(cpu_buf, pc, 0); | |
276 | } | |
277 | ||
1da177e4 LT |
278 | /* |
279 | * This serves to avoid cpu buffer overflow, and makes sure | |
280 | * the task mortuary progresses | |
281 | * | |
282 | * By using schedule_delayed_work_on and then schedule_delayed_work | |
283 | * we guarantee this will stay on the correct cpu | |
284 | */ | |
c4028958 | 285 | static void wq_sync_buffer(struct work_struct *work) |
1da177e4 | 286 | { |
c4028958 DH |
287 | struct oprofile_cpu_buffer * b = |
288 | container_of(work, struct oprofile_cpu_buffer, work.work); | |
1da177e4 LT |
289 | if (b->cpu != smp_processor_id()) { |
290 | printk("WQ on CPU%d, prefer CPU%d\n", | |
291 | smp_processor_id(), b->cpu); | |
292 | } | |
293 | sync_buffer(b->cpu); | |
294 | ||
295 | /* don't re-add the work if we're shutting down */ | |
296 | if (work_enabled) | |
297 | schedule_delayed_work(&b->work, DEFAULT_TIMER_EXPIRE); | |
298 | } |