1// SPDX-License-Identifier: GPL-2.0
2#include "util/cgroup.h"
3#include "util/debug.h"
4#include "util/evlist.h"
5#include "util/machine.h"
6#include "util/map.h"
7#include "util/symbol.h"
8#include "util/target.h"
9#include "util/thread.h"
10#include "util/thread_map.h"
11#include "util/lock-contention.h"
12#include <linux/zalloc.h>
13#include <linux/string.h>
14#include <bpf/bpf.h>
15#include <inttypes.h>
16
17#include "bpf_skel/lock_contention.skel.h"
18#include "bpf_skel/lock_data.h"
19
20static struct lock_contention_bpf *skel;
21
22int lock_contention_prepare(struct lock_contention *con)
23{
24 int i, fd;
25 int ncpus = 1, ntasks = 1, ntypes = 1, naddrs = 1, ncgrps = 1;
26 struct evlist *evlist = con->evlist;
27 struct target *target = con->target;
28
29 skel = lock_contention_bpf__open();
30 if (!skel) {
31 pr_err("Failed to open lock-contention BPF skeleton\n");
32 return -1;
33 }
34
35 bpf_map__set_value_size(skel->maps.stacks, con->max_stack * sizeof(u64));
36 bpf_map__set_max_entries(skel->maps.lock_stat, con->map_nr_entries);
37 bpf_map__set_max_entries(skel->maps.tstamp, con->map_nr_entries);
38
39 if (con->aggr_mode == LOCK_AGGR_TASK)
40 bpf_map__set_max_entries(skel->maps.task_data, con->map_nr_entries);
41 else
42 bpf_map__set_max_entries(skel->maps.task_data, 1);
43
44 if (con->save_callstack)
45 bpf_map__set_max_entries(skel->maps.stacks, con->map_nr_entries);
46 else
47 bpf_map__set_max_entries(skel->maps.stacks, 1);
48
49 if (target__has_cpu(target))
50 ncpus = perf_cpu_map__nr(evlist->core.user_requested_cpus);
51 if (target__has_task(target))
52 ntasks = perf_thread_map__nr(evlist->core.threads);
53 if (con->filters->nr_types)
54 ntypes = con->filters->nr_types;
55 if (con->filters->nr_cgrps)
56 ncgrps = con->filters->nr_cgrps;
57
58 /* resolve lock name filters to addr */
59 if (con->filters->nr_syms) {
60 struct symbol *sym;
61 struct map *kmap;
62 unsigned long *addrs;
63
64 for (i = 0; i < con->filters->nr_syms; i++) {
65 sym = machine__find_kernel_symbol_by_name(con->machine,
66 con->filters->syms[i],
67 &kmap);
68 if (sym == NULL) {
69 pr_warning("ignore unknown symbol: %s\n",
70 con->filters->syms[i]);
71 continue;
72 }
73
74 addrs = realloc(con->filters->addrs,
75 (con->filters->nr_addrs + 1) * sizeof(*addrs));
76 if (addrs == NULL) {
77 pr_warning("memory allocation failure\n");
78 continue;
79 }
80
81 addrs[con->filters->nr_addrs++] = map__unmap_ip(kmap, sym->start);
82 con->filters->addrs = addrs;
83 }
84 naddrs = con->filters->nr_addrs;
85 }
86
87 bpf_map__set_max_entries(skel->maps.cpu_filter, ncpus);
88 bpf_map__set_max_entries(skel->maps.task_filter, ntasks);
89 bpf_map__set_max_entries(skel->maps.type_filter, ntypes);
90 bpf_map__set_max_entries(skel->maps.addr_filter, naddrs);
91 bpf_map__set_max_entries(skel->maps.cgroup_filter, ncgrps);
92
93 if (lock_contention_bpf__load(skel) < 0) {
94 pr_err("Failed to load lock-contention BPF skeleton\n");
95 return -1;
96 }
97
98 if (target__has_cpu(target)) {
99 u32 cpu;
100 u8 val = 1;
101
102 skel->bss->has_cpu = 1;
103 fd = bpf_map__fd(skel->maps.cpu_filter);
104
105 for (i = 0; i < ncpus; i++) {
106 cpu = perf_cpu_map__cpu(evlist->core.user_requested_cpus, i).cpu;
107 bpf_map_update_elem(fd, &cpu, &val, BPF_ANY);
108 }
109 }
110
111 if (target__has_task(target)) {
112 u32 pid;
113 u8 val = 1;
114
115 skel->bss->has_task = 1;
116 fd = bpf_map__fd(skel->maps.task_filter);
117
118 for (i = 0; i < ntasks; i++) {
119 pid = perf_thread_map__pid(evlist->core.threads, i);
120 bpf_map_update_elem(fd, &pid, &val, BPF_ANY);
121 }
122 }
123
124 if (target__none(target) && evlist->workload.pid > 0) {
125 u32 pid = evlist->workload.pid;
126 u8 val = 1;
127
128 skel->bss->has_task = 1;
129 fd = bpf_map__fd(skel->maps.task_filter);
130 bpf_map_update_elem(fd, &pid, &val, BPF_ANY);
131 }
132
133 if (con->filters->nr_types) {
134 u8 val = 1;
135
136 skel->bss->has_type = 1;
137 fd = bpf_map__fd(skel->maps.type_filter);
138
139 for (i = 0; i < con->filters->nr_types; i++)
140 bpf_map_update_elem(fd, &con->filters->types[i], &val, BPF_ANY);
141 }
142
143 if (con->filters->nr_addrs) {
144 u8 val = 1;
145
146 skel->bss->has_addr = 1;
147 fd = bpf_map__fd(skel->maps.addr_filter);
148
149 for (i = 0; i < con->filters->nr_addrs; i++)
150 bpf_map_update_elem(fd, &con->filters->addrs[i], &val, BPF_ANY);
151 }
152
153 if (con->filters->nr_cgrps) {
154 u8 val = 1;
155
156 skel->bss->has_cgroup = 1;
157 fd = bpf_map__fd(skel->maps.cgroup_filter);
158
159 for (i = 0; i < con->filters->nr_cgrps; i++)
160 bpf_map_update_elem(fd, &con->filters->cgrps[i], &val, BPF_ANY);
161 }
162
163 /* these don't work well if in the rodata section */
164 skel->bss->stack_skip = con->stack_skip;
165 skel->bss->aggr_mode = con->aggr_mode;
166 skel->bss->needs_callstack = con->save_callstack;
167 skel->bss->lock_owner = con->owner;
168
169 if (con->aggr_mode == LOCK_AGGR_CGROUP) {
170 if (cgroup_is_v2("perf_event"))
171 skel->bss->use_cgroup_v2 = 1;
172
173 read_all_cgroups(&con->cgroups);
174 }
175
176 bpf_program__set_autoload(skel->progs.collect_lock_syms, false);
177
178 lock_contention_bpf__attach(skel);
179 return 0;
180}
181
182/*
183 * Run the BPF program directly using BPF_PROG_TEST_RUN to update the end
184 * timestamp in ktime so that it can calculate delta easily.
185 */
186static void mark_end_timestamp(void)
187{
188 DECLARE_LIBBPF_OPTS(bpf_test_run_opts, opts,
189 .flags = BPF_F_TEST_RUN_ON_CPU,
190 );
191 int prog_fd = bpf_program__fd(skel->progs.end_timestamp);
192
193 bpf_prog_test_run_opts(prog_fd, &opts);
194}
195
196static void update_lock_stat(int map_fd, int pid, u64 end_ts,
197 enum lock_aggr_mode aggr_mode,
198 struct tstamp_data *ts_data)
199{
200 u64 delta;
201 struct contention_key stat_key = {};
202 struct contention_data stat_data;
203
204 if (ts_data->timestamp >= end_ts)
205 return;
206
207 delta = end_ts - ts_data->timestamp;
208
209 switch (aggr_mode) {
210 case LOCK_AGGR_CALLER:
211 stat_key.stack_id = ts_data->stack_id;
212 break;
213 case LOCK_AGGR_TASK:
214 stat_key.pid = pid;
215 break;
216 case LOCK_AGGR_ADDR:
217 stat_key.lock_addr_or_cgroup = ts_data->lock;
218 break;
219 case LOCK_AGGR_CGROUP:
220 /* TODO */
221 return;
222 default:
223 return;
224 }
225
226 if (bpf_map_lookup_elem(map_fd, &stat_key, &stat_data) < 0)
227 return;
228
229 stat_data.total_time += delta;
230 stat_data.count++;
231
232 if (delta > stat_data.max_time)
233 stat_data.max_time = delta;
234 if (delta < stat_data.min_time)
235 stat_data.min_time = delta;
236
237 bpf_map_update_elem(map_fd, &stat_key, &stat_data, BPF_EXIST);
238}
239
240/*
241 * Account entries in the tstamp map (which didn't see the corresponding
242 * lock:contention_end tracepoint) using end_ts.
243 */
244static void account_end_timestamp(struct lock_contention *con)
245{
246 int ts_fd, stat_fd;
247 int *prev_key, key;
248 u64 end_ts = skel->bss->end_ts;
249 int total_cpus;
250 enum lock_aggr_mode aggr_mode = con->aggr_mode;
251 struct tstamp_data ts_data, *cpu_data;
252
253 /* Iterate per-task tstamp map (key = TID) */
254 ts_fd = bpf_map__fd(skel->maps.tstamp);
255 stat_fd = bpf_map__fd(skel->maps.lock_stat);
256
257 prev_key = NULL;
258 while (!bpf_map_get_next_key(ts_fd, prev_key, &key)) {
259 if (bpf_map_lookup_elem(ts_fd, &key, &ts_data) == 0) {
260 int pid = key;
261
262 if (aggr_mode == LOCK_AGGR_TASK && con->owner)
263 pid = ts_data.flags;
264
265 update_lock_stat(map_fd: stat_fd, pid, end_ts, aggr_mode,
266 ts_data: &ts_data);
267 }
268
269 prev_key = &key;
270 }
271
272 /* Now it'll check per-cpu tstamp map which doesn't have TID. */
273 if (aggr_mode == LOCK_AGGR_TASK || aggr_mode == LOCK_AGGR_CGROUP)
274 return;
275
276 total_cpus = cpu__max_cpu().cpu;
277 ts_fd = bpf_map__fd(skel->maps.tstamp_cpu);
278
279 cpu_data = calloc(total_cpus, sizeof(*cpu_data));
280 if (cpu_data == NULL)
281 return;
282
283 prev_key = NULL;
284 while (!bpf_map_get_next_key(ts_fd, prev_key, &key)) {
285 if (bpf_map_lookup_elem(ts_fd, &key, cpu_data) < 0)
286 goto next;
287
288 for (int i = 0; i < total_cpus; i++) {
289 update_lock_stat(map_fd: stat_fd, pid: -1, end_ts, aggr_mode,
290 ts_data: &cpu_data[i]);
291 }
292
293next:
294 prev_key = &key;
295 }
296 free(cpu_data);
297}
298
299int lock_contention_start(void)
300{
301 skel->bss->enabled = 1;
302 return 0;
303}
304
305int lock_contention_stop(void)
306{
307 skel->bss->enabled = 0;
308 mark_end_timestamp();
309 return 0;
310}
311
312static const char *lock_contention_get_name(struct lock_contention *con,
313 struct contention_key *key,
314 u64 *stack_trace, u32 flags)
315{
316 int idx = 0;
317 u64 addr;
318 const char *name = "";
319 static char name_buf[KSYM_NAME_LEN];
320 struct symbol *sym;
321 struct map *kmap;
322 struct machine *machine = con->machine;
323
324 if (con->aggr_mode == LOCK_AGGR_TASK) {
325 struct contention_task_data task;
326 int pid = key->pid;
327 int task_fd = bpf_map__fd(skel->maps.task_data);
328
329 /* do not update idle comm which contains CPU number */
330 if (pid) {
331 struct thread *t = machine__findnew_thread(machine, /*pid=*/-1, pid);
332
333 if (t == NULL)
334 return name;
335 if (!bpf_map_lookup_elem(task_fd, &pid, &task) &&
336 thread__set_comm(t, task.comm, /*timestamp=*/0))
337 name = task.comm;
338 }
339 return name;
340 }
341
342 if (con->aggr_mode == LOCK_AGGR_ADDR) {
343 int lock_fd = bpf_map__fd(skel->maps.lock_syms);
344
345 /* per-process locks set upper bits of the flags */
346 if (flags & LCD_F_MMAP_LOCK)
347 return "mmap_lock";
348 if (flags & LCD_F_SIGHAND_LOCK)
349 return "siglock";
350
351 /* global locks with symbols */
352 sym = machine__find_kernel_symbol(machine, key->lock_addr_or_cgroup, &kmap);
353 if (sym)
354 return sym->name;
355
356 /* try semi-global locks collected separately */
357 if (!bpf_map_lookup_elem(lock_fd, &key->lock_addr_or_cgroup, &flags)) {
358 if (flags == LOCK_CLASS_RQLOCK)
359 return "rq_lock";
360 }
361
362 return "";
363 }
364
365 if (con->aggr_mode == LOCK_AGGR_CGROUP) {
366 u64 cgrp_id = key->lock_addr_or_cgroup;
367 struct cgroup *cgrp = __cgroup__find(&con->cgroups, cgrp_id);
368
369 if (cgrp)
370 return cgrp->name;
371
372 snprintf(name_buf, sizeof(name_buf), "cgroup:%" PRIu64 "", cgrp_id);
373 return name_buf;
374 }
375
376 /* LOCK_AGGR_CALLER: skip lock internal functions */
377 while (machine__is_lock_function(machine, stack_trace[idx]) &&
378 idx < con->max_stack - 1)
379 idx++;
380
381 addr = stack_trace[idx];
382 sym = machine__find_kernel_symbol(machine, addr, &kmap);
383
384 if (sym) {
385 unsigned long offset;
386
387 offset = map__map_ip(kmap, addr) - sym->start;
388
389 if (offset == 0)
390 return sym->name;
391
392 snprintf(name_buf, sizeof(name_buf), "%s+%#lx", sym->name, offset);
393 } else {
394 snprintf(name_buf, sizeof(name_buf), "%#lx", (unsigned long)addr);
395 }
396
397 return name_buf;
398}
399
400int lock_contention_read(struct lock_contention *con)
401{
402 int fd, stack, err = 0;
403 struct contention_key *prev_key, key = {};
404 struct contention_data data = {};
405 struct lock_stat *st = NULL;
406 struct machine *machine = con->machine;
407 u64 *stack_trace;
408 size_t stack_size = con->max_stack * sizeof(*stack_trace);
409
410 fd = bpf_map__fd(skel->maps.lock_stat);
411 stack = bpf_map__fd(skel->maps.stacks);
412
413 con->fails.task = skel->bss->task_fail;
414 con->fails.stack = skel->bss->stack_fail;
415 con->fails.time = skel->bss->time_fail;
416 con->fails.data = skel->bss->data_fail;
417
418 stack_trace = zalloc(stack_size);
419 if (stack_trace == NULL)
420 return -1;
421
422 account_end_timestamp(con);
423
424 if (con->aggr_mode == LOCK_AGGR_TASK) {
425 struct thread *idle = machine__findnew_thread(machine,
426 /*pid=*/0,
427 /*tid=*/0);
428 thread__set_comm(idle, "swapper", /*timestamp=*/0);
429 }
430
431 if (con->aggr_mode == LOCK_AGGR_ADDR) {
432 DECLARE_LIBBPF_OPTS(bpf_test_run_opts, opts,
433 .flags = BPF_F_TEST_RUN_ON_CPU,
434 );
435 int prog_fd = bpf_program__fd(skel->progs.collect_lock_syms);
436
437 bpf_prog_test_run_opts(prog_fd, &opts);
438 }
439
440 /* make sure it loads the kernel map */
441 maps__load_first(machine->kmaps);
442
443 prev_key = NULL;
444 while (!bpf_map_get_next_key(fd, prev_key, &key)) {
445 s64 ls_key;
446 const char *name;
447
448 /* to handle errors in the loop body */
449 err = -1;
450
451 bpf_map_lookup_elem(fd, &key, &data);
452 if (con->save_callstack) {
453 bpf_map_lookup_elem(stack, &key.stack_id, stack_trace);
454
455 if (!match_callstack_filter(machine, stack_trace)) {
456 con->nr_filtered += data.count;
457 goto next;
458 }
459 }
460
461 switch (con->aggr_mode) {
462 case LOCK_AGGR_CALLER:
463 ls_key = key.stack_id;
464 break;
465 case LOCK_AGGR_TASK:
466 ls_key = key.pid;
467 break;
468 case LOCK_AGGR_ADDR:
469 case LOCK_AGGR_CGROUP:
470 ls_key = key.lock_addr_or_cgroup;
471 break;
472 default:
473 goto next;
474 }
475
476 st = lock_stat_find(ls_key);
477 if (st != NULL) {
478 st->wait_time_total += data.total_time;
479 if (st->wait_time_max < data.max_time)
480 st->wait_time_max = data.max_time;
481 if (st->wait_time_min > data.min_time)
482 st->wait_time_min = data.min_time;
483
484 st->nr_contended += data.count;
485 if (st->nr_contended)
486 st->avg_wait_time = st->wait_time_total / st->nr_contended;
487 goto next;
488 }
489
490 name = lock_contention_get_name(con, key: &key, stack_trace, flags: data.flags);
491 st = lock_stat_findnew(ls_key, name, data.flags);
492 if (st == NULL)
493 break;
494
495 st->nr_contended = data.count;
496 st->wait_time_total = data.total_time;
497 st->wait_time_max = data.max_time;
498 st->wait_time_min = data.min_time;
499
500 if (data.count)
501 st->avg_wait_time = data.total_time / data.count;
502
503 if (con->aggr_mode == LOCK_AGGR_CALLER && verbose > 0) {
504 st->callstack = memdup(stack_trace, stack_size);
505 if (st->callstack == NULL)
506 break;
507 }
508
509next:
510 prev_key = &key;
511
512 /* we're fine now, reset the error */
513 err = 0;
514 }
515
516 free(stack_trace);
517
518 return err;
519}
520
521int lock_contention_finish(struct lock_contention *con)
522{
523 if (skel) {
524 skel->bss->enabled = 0;
525 lock_contention_bpf__destroy(skel);
526 }
527
528 while (!RB_EMPTY_ROOT(&con->cgroups)) {
529 struct rb_node *node = rb_first(&con->cgroups);
530 struct cgroup *cgrp = rb_entry(node, struct cgroup, node);
531
532 rb_erase(node, &con->cgroups);
533 cgroup__put(cgrp);
534 }
535
536 return 0;
537}
538

source code of linux/tools/perf/util/bpf_lock_contention.c