sched_policy.c revision 0384a98d6f61fa47ffde01c15e552f738e88fb94 
1
2/* libs/cutils/sched_policy.c
3**
4** Copyright 2007, The Android Open Source Project
5**
6** Licensed under the Apache License, Version 2.0 (the "License");
7** you may not use this file except in compliance with the License.
8** You may obtain a copy of the License at
9**
10**     http://www.apache.org/licenses/LICENSE-2.0
11**
12** Unless required by applicable law or agreed to in writing, software
13** distributed under the License is distributed on an "AS IS" BASIS,
14** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15** See the License for the specific language governing permissions and
16** limitations under the License.
17*/
18
19#include <stdio.h>
20#include <stdlib.h>
21#include <unistd.h>
22#include <string.h>
23#include <errno.h>
24#include <fcntl.h>
25
26#ifdef HAVE_SCHED_H
27
28#include <sched.h>
29
30#include <cutils/sched_policy.h>
31
32#ifndef SCHED_NORMAL
33  #define SCHED_NORMAL 0
34#endif
35
36#ifndef SCHED_BATCH
37  #define SCHED_BATCH 3
38#endif
39
40static int add_tid_to_cgroup(int tid, const char *grp_name)
41{
42    int fd;
43    char path[255];
44    char text[64];
45
46    sprintf(path, "/dev/cpuctl/%s/tasks", grp_name);
47
48    if ((fd = open(path, O_WRONLY)) < 0)
49        return -1;
50
51    sprintf(text, "%d", tid);
52    if (write(fd, text, strlen(text)) < 0) {
53        close(fd);
54        return -1;
55    }
56
57    close(fd);
58    return 0;
59}
60
61int set_sched_policy(int tid, SchedPolicy policy)
62{
63    static int __sys_supports_schedgroups = -1;
64
65    if (__sys_supports_schedgroups < 0) {
66        if (!access("/dev/cpuctl/tasks", F_OK)) {
67            __sys_supports_schedgroups = 1;
68        } else {
69            __sys_supports_schedgroups = 0;
70        }
71    }
72
73    if (__sys_supports_schedgroups) {
74        const char *grp = NULL;
75
76        if (policy == SP_BACKGROUND) {
77            grp = "bg_non_interactive";
78        }
79
80        if (add_tid_to_cgroup(tid, grp)) {
81            if (errno != ESRCH && errno != ENOENT)
82                return -errno;
83        }
84    } else {
85        struct sched_param param;
86
87        param.sched_priority = 0;
88        sched_setscheduler(tid,
89                           (policy == SP_BACKGROUND) ?
90                            SCHED_BATCH : SCHED_NORMAL,
91                           &param);
92    }
93
94    return 0;
95}
96
97#endif /* HAVE_SCHED_H */
98