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| 1 | +Dynamic SchedTune Boost |
| 2 | + |
| 3 | +=============== |
| 4 | +1. INTRODUCTION |
| 5 | +=============== |
| 6 | + |
| 7 | +Dynamic SchedTune Boost (herein referred to as DSB) extends the SchedTune |
| 8 | +framework and provides APIs to activate and reset SchedTune boosting. |
| 9 | + |
| 10 | +DSB effectively handles multiple concurrent boost requests for each SchedTune |
| 11 | +group. For a particular SchedTune group, its overall boost value will be the |
| 12 | +maximum boost value of all its ongoing concurrent boost requests. |
| 13 | + |
| 14 | +A slot-based system is used to keep track of all boost requests that have been |
| 15 | +made. The number of boost slots available for each SchedTune group is defined |
| 16 | +by 'DYNAMIC_BOOST_SLOTS_COUNT'. Please see the example further below for details |
| 17 | +on how multiple boost requests are handled by the slot-based system. |
| 18 | + |
| 19 | +It is important that every boost request must be reset when no longer needed, |
| 20 | +otherwise the SchedTune group will remain in a permanently boosted state. |
| 21 | +It is up to the developer to implement this properly. |
| 22 | + |
| 23 | + |
| 24 | +====== |
| 25 | +2. API |
| 26 | +====== |
| 27 | + |
| 28 | + int do_stune_boost(char *st_name, int boost, int *slot); |
| 29 | + |
| 30 | + Boost 'st_name' SchedTune cgroup to the given 'boost' value. A slot is |
| 31 | + assigned for this new boost request. Returns 0 on success. |
| 32 | + |
| 33 | + int do_stune_sched_boost(char *st_name, int *slot); |
| 34 | + |
| 35 | + Boost 'st_name' SchedTune cgroup to the boost value specified in |
| 36 | + /dev/stune/{st_name}/schedtune.sched_boost. A slot is assigned for this new |
| 37 | + boost request. Returns 0 on success. |
| 38 | + |
| 39 | + int reset_stune_boost(char *st_name, int slot); |
| 40 | + |
| 41 | + Resets the boost request for the specified 'slot' of the 'st_name' SchedTune |
| 42 | + group. The default boost value of the 'st_name' SchedTune group will be |
| 43 | + restored if there are no more ongoing boost requests. Otherwise, the boost |
| 44 | + value will be set to the maximum boost value of the remaining active boost |
| 45 | + requests. Returns 0 on success. |
| 46 | + |
| 47 | + |
| 48 | +========== |
| 49 | +3. EXAMPLE |
| 50 | +========== |
| 51 | + |
| 52 | +The following example shows how DSB handles three concurrent boost requests for |
| 53 | +the 'top-app' SchedTune group. |
| 54 | + |
| 55 | + |
| 56 | + /* |
| 57 | + * [INITIAL STATE] |
| 58 | + * |
| 59 | + * +---------+ |
| 60 | + * active_boost_slots | Empty | |
| 61 | + * +---------+ |
| 62 | + * +---------+ +---------+ +---------+ +---------+ |
| 63 | + * available_boost_slots | Slot 0 | | Slot 1 | | Slot 2 | | Slot 3 | |
| 64 | + * +---------+ +---------+ +---------+ +---------+ |
| 65 | + * |
| 66 | + * Current boost value: 0 |
| 67 | + */ |
| 68 | + |
| 69 | + /* |
| 70 | + * Create a slot for each boost request |
| 71 | + */ |
| 72 | + int slotFirst, slotSecond, slotThird; |
| 73 | + |
| 74 | + |
| 75 | + do_stune_boost("top-app", 10, &slotFirst); |
| 76 | + /* |
| 77 | + * [1ST BOOST REQUEST] |
| 78 | + * |
| 79 | + * +---------+ |
| 80 | + * | Slot 0 | |
| 81 | + * active_boost_slots +---------+ |
| 82 | + * |boost: 10| |
| 83 | + * +---------+ |
| 84 | + * +---------+ +---------+ +---------+ |
| 85 | + * available_boost_slots | Slot 1 | | Slot 2 | | Slot 3 | |
| 86 | + * +---------+ +---------+ +---------+ |
| 87 | + * |
| 88 | + * Current boost value: 10 |
| 89 | + */ |
| 90 | + |
| 91 | + |
| 92 | + do_stune_boost("top-app", 5, &slotSecond); |
| 93 | + /* |
| 94 | + * [2ND BOOST REQUEST] |
| 95 | + * |
| 96 | + * +---------+ +---------+ |
| 97 | + * | Slot 0 | | Slot 1 | |
| 98 | + * active_boost_slots +---------+ +---------+ |
| 99 | + * |boost: 10| |boost: 5 | |
| 100 | + * +---------+ +---------+ |
| 101 | + * +---------+ +---------+ |
| 102 | + * available_boost_slots | Slot 2 | | Slot 3 | |
| 103 | + * +---------+ +---------+ |
| 104 | + * |
| 105 | + * Current boost value: 10 |
| 106 | + */ |
| 107 | + |
| 108 | + |
| 109 | + do_stune_boost("top-app", 20, &slotThird); |
| 110 | + /* |
| 111 | + * [3RD BOOST REQUEST] |
| 112 | + * |
| 113 | + * +---------+ +---------+ +---------+ |
| 114 | + * | Slot 0 | | Slot 1 | | Slot 2 | |
| 115 | + * active_boost_slots +---------+ +---------+ +---------+ |
| 116 | + * |boost: 10| |boost: 5 | |boost: 20| |
| 117 | + * +---------+ +---------+ +---------+ |
| 118 | + * +---------+ |
| 119 | + * available_boost_slots | Slot 3 | |
| 120 | + * +---------+ |
| 121 | + * |
| 122 | + * Current boost value: 20 |
| 123 | + */ |
| 124 | + |
| 125 | + |
| 126 | + reset_stune_boost("top-app", slotSecond); |
| 127 | + /* |
| 128 | + * [RESET 2ND BOOST REQUEST] |
| 129 | + * |
| 130 | + * +---------+ +---------+ |
| 131 | + * | Slot 0 | | Slot 2 | |
| 132 | + * active_boost_slots +---------+ +---------+ |
| 133 | + * |boost: 10| |boost: 20| |
| 134 | + * +---------+ +---------+ |
| 135 | + * +---------+ +---------+ |
| 136 | + * available_boost_slots | Slot 3 | | Slot 1 | |
| 137 | + * +---------+ +---------+ |
| 138 | + * |
| 139 | + * Current boost value: 20 |
| 140 | + */ |
| 141 | + |
| 142 | + |
| 143 | + reset_stune_boost("top-app", slotThird); |
| 144 | + /* |
| 145 | + * [RESET 3RD BOOST REQUEST] |
| 146 | + * |
| 147 | + * +---------+ |
| 148 | + * | Slot 0 | |
| 149 | + * active_boost_slots +---------+ |
| 150 | + * |boost: 10| |
| 151 | + * +---------+ |
| 152 | + * +---------+ +---------+ +---------+ |
| 153 | + * available_boost_slots | Slot 3 | | Slot 1 | | Slot 2 | |
| 154 | + * +---------+ +---------+ +---------+ |
| 155 | + * |
| 156 | + * Current boost value: 10 |
| 157 | + */ |
| 158 | + |
| 159 | + |
| 160 | + reset_stune_boost("top-app", slotFirst); |
| 161 | + /* |
| 162 | + * [RESET 1ST BOOST REQUEST] |
| 163 | + * |
| 164 | + * +---------+ |
| 165 | + * active_boost_slots | Empty | |
| 166 | + * +---------+ |
| 167 | + * +---------+ +---------+ +---------+ +---------+ |
| 168 | + * available_boost_slots | Slot 3 | | Slot 1 | | Slot 2 | | Slot 0 | |
| 169 | + * +---------+ +---------+ +---------+ +---------+ |
| 170 | + * |
| 171 | + * Current boost value: 0 |
| 172 | + */ |
| 173 | + |
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