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Commit 493dad96 authored by San Mehat's avatar San Mehat
Browse files

libcutils: Add abstracted support for setting scheduler policies 


Also changes the background policy to use SCHED_BATCH. IDLEPRIO
can cause 100% starvation.

Signed-off-by: default avatarSan Mehat <san@google.com>
parent 25f1a5aa

include/cutils/sched_policy.h

0 → 100644
+35 −0
Original line number Diff line number Diff line 
/*

 * Copyright (C) 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.

 */



#ifndef __CUTILS_SCHED_POLICY_H

#define __CUTILS_SCHED_POLICY_H



#ifdef __cplusplus

extern "C" {

#endif



typedef enum {

    SP_BACKGROUND = 0,

    SP_FOREGROUND = 1,

} SchedPolicy;



extern int set_sched_policy(int tid, SchedPolicy policy);



#ifdef __cplusplus

}

#endif



#endif /* __CUTILS_SCHED_POLICY_H */

libcutils/Android.mk

+2 −1
Original line number Diff line number Diff line
@@ -36,7 +36,8 @@ commonSources := \ 
	record_stream.c \

	process_name.c \

	properties.c \

	threads.c

	threads.c \

	sched_policy.c



commonHostSources := \

        ashmem-host.c

libcutils/sched_policy.c

0 → 100644
+84 −0
Original line number Diff line number Diff line 
/* libs/cutils/sched_policy.c

**

** 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.

*/



#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <string.h>

#include <errno.h>

#include <fcntl.h>

#include <sched.h>

#include <linux/sched.h>



#include <cutils/sched_policy.h>



static int add_tid_to_cgroup(int tid, const char *grp_name)

{

    int fd;

    char path[255];

    char text[64];



    sprintf(path, "/dev/cpuctl/%s/tasks", grp_name);



    if ((fd = open(path, O_WRONLY)) < 0)

        return -1;



    sprintf(text, "%d", tid);

    if (write(fd, text, strlen(text)) < 0) {

        close(fd);

        return -1;

    }



    close(fd);

    return 0;

}



int set_sched_policy(int tid, SchedPolicy policy)

{

    static int __sys_supports_schedgroups = -1;



    if (__sys_supports_schedgroups < 0) {

        if (!access("/dev/cpuctl/tasks", F_OK)) {

            __sys_supports_schedgroups = 1;

        } else {

            __sys_supports_schedgroups = 0;

        }

    }



    if (__sys_supports_schedgroups) {

        const char *grp = NULL;



        if (policy == SP_BACKGROUND) {

            grp = "bg_non_interactive";

        }



        if (add_tid_to_cgroup(tid, grp)) {

            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;

}