sys/qos.h

   1 /*
   2  * Copyright (c) 2013-2014 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
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  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24 #ifndef _SYS_QOS_H
  25 #define _SYS_QOS_H
  26
  27 #include <sys/cdefs.h>
  28 #include <Availability.h>
  29
  30 /*!
  31  * @typedef qos_class_t
  32  *
  33  * @abstract
  34  * An abstract thread quality of service (QOS) classification.
  35  *
  36  * @discussion
  37  * Thread quality of service (QOS) classes are ordered abstract representations
  38  * of the nature of work that is expected to be performed by a pthread, dispatch
  39  * queue, or NSOperation. Each class specifies a maximum thread scheduling
  40  * priority for that band (which may be used in combination with a relative
  41  * priority offset within the band), as well as quality of service
  42  * characteristics for timer latency, CPU throughput, I/O throughput, network
  43  * socket traffic management behavior and more.
  44  *
  45  * A best effort is made to allocate available system resources to every QOS
  46  * class. Quality of service degredation only occurs during system resource
  47  * contention, proportionally to the QOS class. That said, QOS classes
  48  * representing user-initiated work attempt to achieve peak throughput while
  49  * QOS classes for other work attempt to achieve peak energy and thermal
  50  * efficiency, even in the absence of contention. Finally, the use of QOS
  51  * classes does not allow threads to supersede any limits that may be applied
  52  * to the overall process.
  53  */
  54
  55 /*!
  56  * @constant QOS_CLASS_USER_INTERACTIVE
  57  * @abstract A QOS class which indicates work performed by this thread
  58  * is interactive with the user.
  59  * @discussion Such work is requested to run at high priority relative to other
  60  * work on the system. Specifying this QOS class is a request to run with
  61  * nearly all available system CPU and I/O bandwidth even under contention.
  62  * This is not an energy-efficient QOS class to use for large tasks. The use of
  63  * this QOS class should be limited to critical interaction with the user such
  64  * as handling events on the main event loop, view drawing, animation, etc.
  65  *
  66  * @constant QOS_CLASS_USER_INITIATED
  67  * @abstract A QOS class which indicates work performed by this thread
  68  * was initiated by the user and that the user is likely waiting for the
  69  * results.
  70  * @discussion Such work is requested to run at a priority below critical user-
  71  * interactive work, but relatively higher than other work on the system. This
  72  * is not an energy-efficient QOS class to use for large tasks and the use of
  73  * this QOS class should be limited to operations where the user is immediately
  74  * waiting for the results.
  75  *
  76  * @constant QOS_CLASS_DEFAULT
  77  * @abstract A default QOS class used by the system in cases where more specific
  78  * QOS class information is not available.
  79  * @discussion Such work is requested to run at a priority below critical user-
  80  * interactive and user-initiated work, but relatively higher than utility and
  81  * background tasks. Threads created by pthread_create() without an attribute
  82  * specifying a QOS class will default to QOS_CLASS_DEFAULT. This QOS class
  83  * value is not intended to be used as a work classification, it should only be
  84  * set when propagating or restoring QOS class values provided by the system.
  85  *
  86  * @constant QOS_CLASS_UTILITY
  87  * @abstract A QOS class which indicates work performed by this thread
  88  * may or may not be initiated by the user and that the user is unlikely to be
  89  * immediately waiting for the results.
  90  * @discussion Such work is requested to run at a priority below critical user-
  91  * interactive and user-initiated work, but relatively higher than low-level
  92  * system maintenance tasks. The use of this QOS class indicates the work should
  93  * be run in an energy and thermally-efficient manner.
  94  *
  95  * @constant QOS_CLASS_BACKGROUND
  96  * @abstract A QOS class which indicates work performed by this thread was not
  97  * initiated by the user and that the user may be unaware of the results.
  98  * @discussion Such work is requested to run at a priority below other work.
  99  * The use of this QOS class indicates the work should be run in the most energy
 100  * and thermally-efficient manner.
 101  *
 102  * @constant QOS_CLASS_UNSPECIFIED
 103  * @abstract A QOS class value which indicates the absence or removal of QOS
 104  * class information.
 105  * @discussion As an API return value, may indicate that threads or pthread
 106  * attributes were configured with legacy API incompatible or in conflict with
 107  * the QOS class system.
 108  */
 109
 110 #define __QOS_ENUM(name, type, ...) enum { __VA_ARGS__ }; typedef type name##_t
 111 #define __QOS_CLASS_AVAILABLE_STARTING(...)
 112
 113 #if defined(__has_feature) && defined(__has_extension)
 114 #if __has_feature(objc_fixed_enum) || __has_extension(cxx_strong_enums)
 115 #undef __QOS_ENUM
 116 #define __QOS_ENUM(name, type, ...) typedef enum : type { __VA_ARGS__ } name##_t
 117 #endif
 118 #if __has_feature(enumerator_attributes)
 119 #undef __QOS_CLASS_AVAILABLE_STARTING
 120 #define __QOS_CLASS_AVAILABLE_STARTING __OSX_AVAILABLE_STARTING
 121 #endif
 122 #endif
 123
 124 __QOS_ENUM(qos_class, unsigned int,
 125         QOS_CLASS_USER_INTERACTIVE
 126                         __QOS_CLASS_AVAILABLE_STARTING(__MAC_10_10, __IPHONE_8_0) = 0x21,
 127         QOS_CLASS_USER_INITIATED
 128                         __QOS_CLASS_AVAILABLE_STARTING(__MAC_10_10, __IPHONE_8_0) = 0x19,
 129         QOS_CLASS_DEFAULT
 130                         __QOS_CLASS_AVAILABLE_STARTING(__MAC_10_10, __IPHONE_8_0) = 0x15,
 131         QOS_CLASS_UTILITY
 132                         __QOS_CLASS_AVAILABLE_STARTING(__MAC_10_10, __IPHONE_8_0) = 0x11,
 133         QOS_CLASS_BACKGROUND
 134                         __QOS_CLASS_AVAILABLE_STARTING(__MAC_10_10, __IPHONE_8_0) = 0x09,
 135         QOS_CLASS_UNSPECIFIED
 136                         __QOS_CLASS_AVAILABLE_STARTING(__MAC_10_10, __IPHONE_8_0) = 0x00,
 137 );
 138
 139 #undef __QOS_ENUM
 140
 141 /*!
 142  * @constant QOS_MIN_RELATIVE_PRIORITY
 143  * @abstract The minimum relative priority that may be specified within a
 144  * QOS class. These priorities are relative only within a given QOS class
 145  * and meaningful only for the current process.
 146  */
 147 #define QOS_MIN_RELATIVE_PRIORITY (-15)
 148
 149 /* Userspace (only) definitions */
 150
 151 #ifndef KERNEL
 152
 153 __BEGIN_DECLS
 154
 155 /*!
 156  * @function qos_class_self
 157  *
 158  * @abstract
 159  * Returns the requested QOS class of the current thread.
 160  *
 161  * @return
 162  * One of the QOS class values in qos_class_t.
 163  */
 164 __OSX_AVAILABLE_STARTING(__MAC_10_10, __IPHONE_8_0)
 165 qos_class_t
 166 qos_class_self(void);
 167
 168 /*!
 169  * @function qos_class_main
 170  *
 171  * @abstract
 172  * Returns the initial requested QOS class of the main thread.
 173  *
 174  * @discussion
 175  * The QOS class that the main thread of a process is created with depends on
 176  * the type of process (e.g. application or daemon) and on how it has been
 177  * launched.
 178  *
 179  * This function returns that initial requested QOS class value chosen by the
 180  * system to enable propagation of that classification to matching work not
 181  * executing on the main thread.
 182  *
 183  * @return
 184  * One of the QOS class values in qos_class_t.
 185  */
 186 __OSX_AVAILABLE_STARTING(__MAC_10_10, __IPHONE_8_0)
 187 qos_class_t
 188 qos_class_main(void);
 189
 190 __END_DECLS
 191
 192 #endif // KERNEL
 193
 194 #endif // _SYS_QOS_H