summaryrefslogtreecommitdiffstats
path: root/libcutils/sched_policy.c
blob: 12fc7341aea1a0e700b84c91d97c8ad4ed51293d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
/*
** Copyright 2007, The Android Open Source Project
**
** Licensed under the Apache License, Version 2.0 (the "License"); 
** you may not use this file except in compliance with the License. 
** You may obtain a copy of the License at 
**
**     http://www.apache.org/licenses/LICENSE-2.0 
**
** Unless required by applicable law or agreed to in writing, software 
** distributed under the License is distributed on an "AS IS" BASIS, 
** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
** See the License for the specific language governing permissions and 
** limitations under the License.
*/

#define LOG_TAG "SchedPolicy"

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <cutils/sched_policy.h>
#include <log/log.h>

#define UNUSED __attribute__((__unused__))

/* Re-map SP_DEFAULT to the system default policy, and leave other values unchanged.
 * Call this any place a SchedPolicy is used as an input parameter.
 * Returns the possibly re-mapped policy.
 */
static inline SchedPolicy _policy(SchedPolicy p)
{
   return p == SP_DEFAULT ? SP_SYSTEM_DEFAULT : p;
}

#if defined(HAVE_ANDROID_OS) && defined(HAVE_SCHED_H) && defined(HAVE_PTHREADS)

#include <sched.h>
#include <pthread.h>

#ifndef SCHED_NORMAL
  #define SCHED_NORMAL 0
#endif

#ifndef SCHED_BATCH
  #define SCHED_BATCH 3
#endif

#define POLICY_DEBUG 0

#define CAN_SET_SP_SYSTEM 0 // non-zero means to implement set_sched_policy(tid, SP_SYSTEM)

static pthread_once_t the_once = PTHREAD_ONCE_INIT;

static int __sys_supports_schedgroups = -1;

// File descriptors open to /dev/cpuctl/../tasks, setup by initialize, or -1 on error.
static int bg_cgroup_fd = -1;
static int fg_cgroup_fd = -1;
#if CAN_SET_SP_SYSTEM
static int system_cgroup_fd = -1;
#endif

/* Add tid to the scheduling group defined by the policy */
static int add_tid_to_cgroup(int tid, SchedPolicy policy)
{
    int fd;

    switch (policy) {
    case SP_BACKGROUND:
        fd = bg_cgroup_fd;
        break;
    case SP_FOREGROUND:
    case SP_AUDIO_APP:
    case SP_AUDIO_SYS:
        fd = fg_cgroup_fd;
        break;
#if CAN_SET_SP_SYSTEM
    case SP_SYSTEM:
        fd = system_cgroup_fd;
        break;
#endif
    default:
        fd = -1;
        break;
    }

    if (fd < 0) {
        SLOGE("add_tid_to_cgroup failed; policy=%d\n", policy);
        return -1;
    }

    // specialized itoa -- works for tid > 0
    char text[22];
    char *end = text + sizeof(text) - 1;
    char *ptr = end;
    *ptr = '\0';
    while (tid > 0) {
        *--ptr = '0' + (tid % 10);
        tid = tid / 10;
    }

    if (write(fd, ptr, end - ptr) < 0) {
        /*
         * If the thread is in the process of exiting,
         * don't flag an error
         */
        if (errno == ESRCH)
                return 0;
        SLOGW("add_tid_to_cgroup failed to write '%s' (%s); policy=%d\n",
              ptr, strerror(errno), policy);
        return -1;
    }

    return 0;
}

static void __initialize(void) {
    char* filename;
    if (!access("/dev/cpuctl/tasks", F_OK)) {
        __sys_supports_schedgroups = 1;

#if CAN_SET_SP_SYSTEM
        filename = "/dev/cpuctl/tasks";
        system_cgroup_fd = open(filename, O_WRONLY | O_CLOEXEC);
        if (system_cgroup_fd < 0) {
            SLOGV("open of %s failed: %s\n", filename, strerror(errno));
        }
#endif

        filename = "/dev/cpuctl/apps/tasks";
        fg_cgroup_fd = open(filename, O_WRONLY | O_CLOEXEC);
        if (fg_cgroup_fd < 0) {
            SLOGE("open of %s failed: %s\n", filename, strerror(errno));
        }

        filename = "/dev/cpuctl/apps/bg_non_interactive/tasks";
        bg_cgroup_fd = open(filename, O_WRONLY | O_CLOEXEC);
        if (bg_cgroup_fd < 0) {
            SLOGE("open of %s failed: %s\n", filename, strerror(errno));
        }
    } else {
        __sys_supports_schedgroups = 0;
    }
}

/*
 * Try to get the scheduler group.
 *
 * The data from /proc/<pid>/cgroup looks (something) like:
 *  2:cpu:/bg_non_interactive
 *  1:cpuacct:/
 *
 * We return the part after the "/", which will be an empty string for
 * the default cgroup.  If the string is longer than "bufLen", the string
 * will be truncated.
 */
static int getSchedulerGroup(int tid, char* buf, size_t bufLen)
{
#ifdef HAVE_ANDROID_OS
    char pathBuf[32];
    char lineBuf[256];
    FILE *fp;

    snprintf(pathBuf, sizeof(pathBuf), "/proc/%d/cgroup", tid);
    if (!(fp = fopen(pathBuf, "r"))) {
        return -1;
    }

    while(fgets(lineBuf, sizeof(lineBuf) -1, fp)) {
        char *next = lineBuf;
        char *subsys;
        char *grp;
        size_t len;

        /* Junk the first field */
        if (!strsep(&next, ":")) {
            goto out_bad_data;
        }

        if (!(subsys = strsep(&next, ":"))) {
            goto out_bad_data;
        }

        if (strcmp(subsys, "cpu")) {
            /* Not the subsys we're looking for */
            continue;
        }

        if (!(grp = strsep(&next, ":"))) {
            goto out_bad_data;
        }
        grp++; /* Drop the leading '/' */
        len = strlen(grp);
        grp[len-1] = '\0'; /* Drop the trailing '\n' */

        if (bufLen <= len) {
            len = bufLen - 1;
        }
        strncpy(buf, grp, len);
        buf[len] = '\0';
        fclose(fp);
        return 0;
    }

    SLOGE("Failed to find cpu subsys");
    fclose(fp);
    return -1;
 out_bad_data:
    SLOGE("Bad cgroup data {%s}", lineBuf);
    fclose(fp);
    return -1;
#else
    errno = ENOSYS;
    return -1;
#endif
}

int get_sched_policy(int tid, SchedPolicy *policy)
{
    if (tid == 0) {
        tid = gettid();
    }
    pthread_once(&the_once, __initialize);

    if (__sys_supports_schedgroups) {
        char grpBuf[32];
        if (getSchedulerGroup(tid, grpBuf, sizeof(grpBuf)) < 0)
            return -1;
        if (grpBuf[0] == '\0') {
            *policy = SP_SYSTEM;
        } else if (!strcmp(grpBuf, "apps/bg_non_interactive")) {
            *policy = SP_BACKGROUND;
        } else if (!strcmp(grpBuf, "apps")) {
            *policy = SP_FOREGROUND;
        } else {
            errno = ERANGE;
            return -1;
        }
    } else {
        int rc = sched_getscheduler(tid);
        if (rc < 0)
            return -1;
        else if (rc == SCHED_NORMAL)
            *policy = SP_FOREGROUND;
        else if (rc == SCHED_BATCH)
            *policy = SP_BACKGROUND;
        else {
            errno = ERANGE;
            return -1;
        }
    }
    return 0;
}

int set_sched_policy(int tid, SchedPolicy policy)
{
    if (tid == 0) {
        tid = gettid();
    }
    policy = _policy(policy);
    pthread_once(&the_once, __initialize);

#if POLICY_DEBUG
    char statfile[64];
    char statline[1024];
    char thread_name[255];
    int fd;

    sprintf(statfile, "/proc/%d/stat", tid);
    memset(thread_name, 0, sizeof(thread_name));

    fd = open(statfile, O_RDONLY);
    if (fd >= 0) {
        int rc = read(fd, statline, 1023);
        close(fd);
        statline[rc] = 0;
        char *p = statline;
        char *q;

        for (p = statline; *p != '('; p++);
        p++;
        for (q = p; *q != ')'; q++);

        strncpy(thread_name, p, (q-p));
    }
    switch (policy) {
    case SP_BACKGROUND:
        SLOGD("vvv tid %d (%s)", tid, thread_name);
        break;
    case SP_FOREGROUND:
    case SP_AUDIO_APP:
    case SP_AUDIO_SYS:
        SLOGD("^^^ tid %d (%s)", tid, thread_name);
        break;
    case SP_SYSTEM:
        SLOGD("/// tid %d (%s)", tid, thread_name);
        break;
    default:
        SLOGD("??? tid %d (%s)", tid, thread_name);
        break;
    }
#endif

    if (__sys_supports_schedgroups) {
        if (add_tid_to_cgroup(tid, policy)) {
            if (errno != ESRCH && errno != ENOENT)
                return -errno;
        }
    } else {
        struct sched_param param;

        param.sched_priority = 0;
        sched_setscheduler(tid,
                           (policy == SP_BACKGROUND) ?
                            SCHED_BATCH : SCHED_NORMAL,
                           &param);
    }

    return 0;
}

#else

/* Stubs for non-Android targets. */

int set_sched_policy(int tid UNUSED, SchedPolicy policy UNUSED)
{
    return 0;
}

int get_sched_policy(int tid UNUSED, SchedPolicy *policy)
{
    *policy = SP_SYSTEM_DEFAULT;
    return 0;
}

#endif

const char *get_sched_policy_name(SchedPolicy policy)
{
    policy = _policy(policy);
    static const char * const strings[SP_CNT] = {
       [SP_BACKGROUND] = "bg",
       [SP_FOREGROUND] = "fg",
       [SP_SYSTEM]     = "  ",
       [SP_AUDIO_APP]  = "aa",
       [SP_AUDIO_SYS]  = "as",
    };
    if ((policy < SP_CNT) && (strings[policy] != NULL))
        return strings[policy];
    else
        return "error";
}