latencytop.c revision 7341494707810f709855ea85ce03a8ec3ac8dbaf 
1/*
2 * Copyright (C) 2008 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include <ctype.h>
18#include <dirent.h>
19#include <errno.h>
20#include <signal.h>
21#include <stdio.h>
22#include <stdlib.h>
23#include <unistd.h>
24
25#define MAX_LINE 512
26#define MAX_FILENAME 64
27
28const char *EXPECTED_VERSION = "Latency Top version : v0.1\n";
29const char *SYSCTL_FILE = "/proc/sys/kernel/latencytop";
30const char *GLOBAL_STATS_FILE = "/proc/latency_stats";
31const char *THREAD_STATS_FILE_FORMAT = "/proc/%d/task/%d/latency";
32
33struct latency_entry {
34    struct latency_entry *next;
35    unsigned long count;
36    unsigned long max;
37    unsigned long total;
38    char reason[MAX_LINE];
39};
40
41static inline void check_latencytop() { }
42
43static struct latency_entry *read_global_stats(struct latency_entry *list, int erase);
44static struct latency_entry *read_process_stats(struct latency_entry *list, int erase, int pid);
45static struct latency_entry *read_thread_stats(struct latency_entry *list, int erase, int pid, int tid, int fatal);
46
47static struct latency_entry *alloc_latency_entry(void);
48static void free_latency_entry(struct latency_entry *e);
49
50static void set_latencytop(int on);
51static struct latency_entry *read_latency_file(FILE *f, struct latency_entry *list);
52static void erase_latency_file(FILE *f);
53
54static struct latency_entry *find_latency_entry(struct latency_entry *e, char *reason);
55static void print_latency_entries(struct latency_entry *head);
56
57static void signal_handler(int sig);
58static void disable_latencytop(void);
59
60static int numcmp(const long long a, const long long b);
61static int lat_cmp(const void *a, const void *b);
62
63static void clear_screen(void);
64static void usage(const char *cmd);
65
66struct latency_entry *free_entries;
67
68int main(int argc, char *argv[]) {
69    struct latency_entry *e;
70    int delay, iterations;
71    int pid, tid;
72    int count, erase;
73    int i;
74
75    delay = 1;
76    iterations = 0;
77    pid = tid = 0;
78
79    for (i = 1; i < argc; i++) {
80        if (!strcmp(argv[i], "-d")) {
81            if (i >= argc - 1) {
82                fprintf(stderr, "Option -d expects an argument.\n");
83                exit(EXIT_FAILURE);
84            }
85            delay = atoi(argv[++i]);
86            continue;
87        }
88        if (!strcmp(argv[i], "-n")) {
89            if (i >= argc - 1) {
90                fprintf(stderr, "Option -n expects an argument.\n");
91                exit(EXIT_FAILURE);
92            }
93            iterations = atoi(argv[++i]);
94            continue;
95        }
96        if (!strcmp(argv[i], "-h")) {
97            usage(argv[0]);
98            exit(EXIT_SUCCESS);
99        }
100        if (!strcmp(argv[i], "-p")) {
101            if (i >= argc - 1) {
102                fprintf(stderr, "Option -p expects an argument.\n");
103                exit(EXIT_FAILURE);
104            }
105            pid = atoi(argv[++i]);
106            continue;
107        }
108        if (!strcmp(argv[i], "-t")) {
109            if (i >= argc - 1) {
110                fprintf(stderr, "Option -t expects an argument.\n");
111                exit(EXIT_FAILURE);
112            }
113            tid = atoi(argv[++i]);
114            continue;
115        }
116        fprintf(stderr, "Invalid argument \"%s\".\n", argv[i]);
117        usage(argv[0]);
118        exit(EXIT_FAILURE);
119    }
120
121    if (tid && !pid) {
122        fprintf(stderr, "If you provide a thread ID with -t, you must provide a process ID with -p.\n");
123        exit(EXIT_FAILURE);
124    }
125
126    check_latencytop();
127
128    free_entries = NULL;
129
130    signal(SIGINT, &signal_handler);
131    signal(SIGTERM, &signal_handler);
132
133    atexit(&disable_latencytop);
134
135    set_latencytop(1);
136
137    count = 0;
138    erase = 1;
139
140    while ((iterations == 0) || (count++ < iterations)) {
141
142        sleep(delay);
143
144        e = NULL;
145        if (pid) {
146            if (tid) {
147                e = read_thread_stats(e, erase, pid, tid, 1);
148            } else {
149                e = read_process_stats(e, erase, pid);
150            }
151        } else {
152            e = read_global_stats(e, erase);
153        }
154        erase = 0;
155
156        clear_screen();
157        if (pid) {
158            if (tid) {
159                printf("Latencies for thread %d in process %d:\n", tid, pid);
160            } else {
161                printf("Latencies for process %d:\n", pid);
162            }
163        } else {
164            printf("Latencies across all processes:\n");
165        }
166        print_latency_entries(e);
167    }
168
169    set_latencytop(0);
170
171    return 0;
172}
173
174static struct latency_entry *read_global_stats(struct latency_entry *list, int erase) {
175    FILE *f;
176    struct latency_entry *e;
177
178    if (erase) {
179        f = fopen(GLOBAL_STATS_FILE, "w");
180        if (!f) {
181            fprintf(stderr, "Could not open global latency stats file: %s\n", strerror(errno));
182            exit(EXIT_FAILURE);
183        }
184        fprintf(f, "erase\n");
185        fclose(f);
186    }
187
188    f = fopen(GLOBAL_STATS_FILE, "r");
189    if (!f) {
190        fprintf(stderr, "Could not open global latency stats file: %s\n", strerror(errno));
191        exit(EXIT_FAILURE);
192    }
193
194    e = read_latency_file(f, list);
195
196    fclose(f);
197
198    return e;
199}
200
201static struct latency_entry *read_process_stats(struct latency_entry *list, int erase, int pid) {
202    char dirname[MAX_FILENAME];
203    DIR *dir;
204    struct dirent *ent;
205    struct latency_entry *e;
206    int tid;
207
208    sprintf(dirname, "/proc/%d/task", pid);
209    dir = opendir(dirname);
210    if (!dir) {
211        fprintf(stderr, "Could not open task dir for process %d.\n", pid);
212        fprintf(stderr, "Perhaps the process has terminated?\n");
213        exit(EXIT_FAILURE);
214    }
215
216    e = list;
217    while ((ent = readdir(dir))) {
218        if (!isdigit(ent->d_name[0]))
219            continue;
220
221        tid = atoi(ent->d_name);
222
223        e = read_thread_stats(e, erase, pid, tid, 0);
224    }
225
226    closedir(dir);
227
228    return e;
229}
230
231static struct latency_entry *read_thread_stats(struct latency_entry *list, int erase, int pid, int tid, int fatal) {
232    char filename[MAX_FILENAME];
233    FILE *f;
234    struct latency_entry *e;
235
236    sprintf(filename, THREAD_STATS_FILE_FORMAT, pid, tid);
237
238    if (erase) {
239        f = fopen(filename, "w");
240        if (!f) {
241            if (fatal) {
242                fprintf(stderr, "Could not open %s: %s\n", filename, strerror(errno));
243                fprintf(stderr, "Perhaps the process or thread has terminated?\n");
244                exit(EXIT_FAILURE);
245            } else {
246                return list;
247            }
248        }
249        fprintf(f, "erase\n");
250        fclose(f);
251    }
252
253    f = fopen(GLOBAL_STATS_FILE, "r");
254    if (!f) {
255        if (fatal) {
256            fprintf(stderr, "Could not open %s: %s\n", filename, strerror(errno));
257            fprintf(stderr, "Perhaps the process or thread has terminated?\n");
258            exit(EXIT_FAILURE);
259        } else {
260            return list;
261        }
262    }
263
264    e = read_latency_file(f, list);
265
266    fclose(f);
267
268    return e;
269}
270
271static struct latency_entry *alloc_latency_entry(void) {
272    struct latency_entry *e;
273
274    if (free_entries) {
275        e = free_entries;
276        free_entries = free_entries->next;
277    } else {
278        e = calloc(1, sizeof(struct latency_entry));
279        if (!e) {
280            fprintf(stderr, "Could not allocate latency entry: %s\n", strerror(errno));
281            exit(EXIT_FAILURE);
282        }
283    }
284
285    return e;
286}
287
288static void free_latency_entry(struct latency_entry *e) {
289    e->next = free_entries;
290    free_entries = e;
291}
292
293static struct latency_entry *find_latency_entry(struct latency_entry *head, char *reason) {
294    struct latency_entry *e;
295
296    e = head;
297
298    while (e) {
299        if (!strcmp(e->reason, reason))
300            return e;
301        e = e->next;
302    }
303
304    return NULL;
305}
306
307static void set_latencytop(int on) {
308    FILE *f;
309
310    f = fopen(SYSCTL_FILE, "w");
311    if (!f) {
312        fprintf(stderr, "Could not open %s: %s\n", SYSCTL_FILE, strerror(errno));
313        exit(EXIT_FAILURE);
314    }
315
316    fprintf(f, "%d\n", on);
317
318    fclose(f);
319}
320
321static void erase_latency_file(FILE *f) {
322    fprintf(f, "erase\n");
323}
324
325static struct latency_entry *read_latency_file(FILE *f, struct latency_entry *list) {
326    struct latency_entry *e, *head;
327    char line[MAX_LINE];
328    unsigned long count, max, total;
329    char reason[MAX_LINE];
330
331    head = list;
332
333    if (!fgets(line, MAX_LINE, f)) {
334        fprintf(stderr, "Could not read latency file version: %s\n", strerror(errno));
335        exit(EXIT_FAILURE);
336    }
337
338    if (strcmp(line, EXPECTED_VERSION) != 0) {
339        fprintf(stderr, "Expected version: %s\n", EXPECTED_VERSION);
340        fprintf(stderr, "But got version: %s", line);
341        exit(EXIT_FAILURE);
342    }
343
344    while (fgets(line, MAX_LINE, f)) {
345        sscanf(line, "%ld %ld %ld %s", &count, &total, &max, reason);
346        if (max > 0 || total > 0) {
347            e = find_latency_entry(head, reason);
348            if (e) {
349                e->count += count;
350                if (max > e->max)
351                    e->max = max;
352                e->total += total;
353            } else {
354                e = alloc_latency_entry();
355                e->count = count;
356                e->max = max;
357                e->total = total;
358                strcpy(e->reason, reason);
359                e->next = head;
360                head = e;
361            }
362        }
363    }
364
365    return head;
366}
367
368static void print_latency_entries(struct latency_entry *head) {
369    struct latency_entry *e, **array;
370    unsigned long average;
371    int i, count;
372
373    e = head;
374    count = 0;
375    while (e) {
376        count++;
377        e = e->next;
378    }
379
380    e = head;
381    array = calloc(count, sizeof(struct latency_entry *));
382    if (!array) {
383        fprintf(stderr, "Error allocating array: %s\n", strerror(errno));
384        exit(EXIT_FAILURE);
385    }
386    for (i = 0; i < count; i++) {
387        array[i] = e;
388        e = e->next;
389    }
390
391    qsort(array, count, sizeof(struct latency_entry *), &lat_cmp);
392
393    printf("%10s  %10s  %7s  %s\n", "Maximum", "Average", "Count", "Reason");
394    for (i = 0; i < count; i++) {
395        e = array[i];
396        average = e->total / e->count;
397        printf("%4lu.%02lu ms  %4lu.%02lu ms  %7ld  %s\n",
398            e->max / 1000, (e->max % 1000) / 10,
399            average / 1000, (average % 1000) / 10,
400            e->count,
401            e->reason);
402    }
403
404    free(array);
405}
406
407static void signal_handler(int sig) {
408    exit(EXIT_SUCCESS);
409}
410
411static void disable_latencytop(void) {
412    set_latencytop(0);
413}
414
415static void clear_screen(void) {
416    printf("\n\n");
417}
418
419static void usage(const char *cmd) {
420    fprintf(stderr, "Usage: %s [ -d delay ] [ -n iterations ] [ -p pid [ -t tid ] ] [ -h ]\n"
421                    "    -d delay       Time to sleep between updates.\n"
422                    "    -n iterations  Number of updates to show (0 = infinite).\n"
423                    "    -p pid         Process to monitor (default is all).\n"
424                    "    -t tid         Thread (within specified process) to monitor (default is all).\n"
425                    "    -h             Display this help screen.\n",
426        cmd);
427}
428
429static int numcmp(const long long a, const long long b) {
430    if (a < b) return -1;
431    if (a > b) return 1;
432    return 0;
433}
434
435static int lat_cmp(const void *a, const void *b) {
436    const struct latency_entry *pa, *pb;
437
438    pa = (*((struct latency_entry **)a));
439    pb = (*((struct latency_entry **)b));
440
441    return numcmp(pb->max, pa->max);
442}
443