1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * BPF extensible scheduler class: Documentation/scheduler/sched-ext.rst 4 * 5 * Copyright (c) 2022 Meta Platforms, Inc. and affiliates. 6 * Copyright (c) 2022 Tejun Heo <tj@kernel.org> 7 * Copyright (c) 2022 David Vernet <dvernet@meta.com> 8 */ 9 #ifndef _LINUX_SCHED_EXT_H 10 #define _LINUX_SCHED_EXT_H 11 12 #ifdef CONFIG_SCHED_CLASS_EXT 13 14 #include <linux/llist.h> 15 #include <linux/rhashtable-types.h> 16 17 enum scx_public_consts { 18 SCX_OPS_NAME_LEN = 128, 19 20 /* 21 * %SCX_SLICE_DFL is used to refill slices when the BPF scheduler misses 22 * to set the slice for a task that is selected for execution. 23 * %SCX_EV_REFILL_SLICE_DFL counts the number of times the default slice 24 * refill has been triggered. 25 * 26 * %SCX_SLICE_BYPASS is used as the slice for all tasks in the bypass 27 * mode. As making forward progress for all tasks is the main goal of 28 * the bypass mode, a shorter slice is used. 29 */ 30 SCX_SLICE_DFL = 20 * 1000000, /* 20ms */ 31 SCX_SLICE_BYPASS = 5 * 1000000, /* 5ms */ 32 SCX_SLICE_INF = U64_MAX, /* infinite, implies nohz */ 33 }; 34 35 /* 36 * DSQ (dispatch queue) IDs are 64bit of the format: 37 * 38 * Bits: [63] [62 .. 0] 39 * [ B] [ ID ] 40 * 41 * B: 1 for IDs for built-in DSQs, 0 for ops-created user DSQs 42 * ID: 63 bit ID 43 * 44 * Built-in IDs: 45 * 46 * Bits: [63] [62] [61..32] [31 .. 0] 47 * [ 1] [ L] [ R ] [ V ] 48 * 49 * 1: 1 for built-in DSQs. 50 * L: 1 for LOCAL_ON DSQ IDs, 0 for others 51 * V: For LOCAL_ON DSQ IDs, a CPU number. For others, a pre-defined value. 52 */ 53 enum scx_dsq_id_flags { 54 SCX_DSQ_FLAG_BUILTIN = 1LLU << 63, 55 SCX_DSQ_FLAG_LOCAL_ON = 1LLU << 62, 56 57 SCX_DSQ_INVALID = SCX_DSQ_FLAG_BUILTIN | 0, 58 SCX_DSQ_GLOBAL = SCX_DSQ_FLAG_BUILTIN | 1, 59 SCX_DSQ_LOCAL = SCX_DSQ_FLAG_BUILTIN | 2, 60 SCX_DSQ_BYPASS = SCX_DSQ_FLAG_BUILTIN | 3, 61 SCX_DSQ_REJECT = SCX_DSQ_FLAG_BUILTIN | 4, /* internal - see find_dsq_for_dispatch() */ 62 SCX_DSQ_RESCUE = SCX_DSQ_FLAG_BUILTIN | 5, /* internal - see find_dsq_for_dispatch() */ 63 SCX_DSQ_LOCAL_ON = SCX_DSQ_FLAG_BUILTIN | SCX_DSQ_FLAG_LOCAL_ON, 64 SCX_DSQ_LOCAL_CPU_MASK = 0xffffffffLLU, 65 }; 66 67 struct scx_deferred_reenq_user { 68 struct list_head node; 69 u64 flags; 70 }; 71 72 struct scx_dsq_pcpu { 73 struct scx_dispatch_q *dsq; 74 struct scx_deferred_reenq_user deferred_reenq_user; 75 }; 76 77 /* 78 * A dispatch queue (DSQ) can be either a FIFO or p->scx.dsq_vtime ordered 79 * queue. A built-in DSQ is always a FIFO. The built-in local DSQs are used to 80 * buffer between the scheduler core and the BPF scheduler. See the 81 * documentation for more details. 82 */ 83 struct scx_dispatch_q { 84 raw_spinlock_t lock; 85 struct task_struct __rcu *first_task; /* lockless peek at head */ 86 struct list_head list; /* tasks in dispatch order */ 87 struct rb_root priq; /* used to order by p->scx.dsq_vtime */ 88 u32 nr; 89 u32 seq; /* used by BPF iter */ 90 u64 id; 91 struct rhash_head hash_node; 92 struct llist_node free_node; 93 struct scx_sched *sched; 94 struct scx_dsq_pcpu __percpu *pcpu; 95 struct rcu_head rcu; 96 }; 97 98 /* sched_ext_entity.flags */ 99 enum scx_ent_flags { 100 SCX_TASK_QUEUED = 1 << 0, /* on ext runqueue */ 101 SCX_TASK_IN_CUSTODY = 1 << 1, /* in custody, needs ops.dequeue() when leaving */ 102 SCX_TASK_RESET_RUNNABLE_AT = 1 << 2, /* runnable_at should be reset */ 103 SCX_TASK_DEQD_FOR_SLEEP = 1 << 3, /* last dequeue was for SLEEP */ 104 SCX_TASK_SUB_INIT = 1 << 4, /* task being initialized for a sub sched */ 105 SCX_TASK_IMMED = 1 << 5, /* task is on local DSQ with %SCX_ENQ_IMMED */ 106 SCX_TASK_PROTECTED = 1 << 6, /* slice and DSQ head position protected */ 107 108 /* 109 * Bits 8 to 10 are used to carry task state: 110 * 111 * NONE ops.init_task() not called yet 112 * INIT_BEGIN ops.init_task() in flight; see sched_ext_dead() 113 * INIT ops.init_task() succeeded, but task can be cancelled 114 * READY fully initialized, but not in sched_ext 115 * ENABLED fully initialized and in sched_ext 116 * DEAD terminal state set by sched_ext_dead() 117 */ 118 SCX_TASK_STATE_SHIFT = 8, 119 SCX_TASK_STATE_BITS = 3, 120 SCX_TASK_STATE_MASK = ((1 << SCX_TASK_STATE_BITS) - 1) << SCX_TASK_STATE_SHIFT, 121 122 SCX_TASK_NONE = 0 << SCX_TASK_STATE_SHIFT, 123 SCX_TASK_INIT_BEGIN = 1 << SCX_TASK_STATE_SHIFT, 124 SCX_TASK_INIT = 2 << SCX_TASK_STATE_SHIFT, 125 SCX_TASK_READY = 3 << SCX_TASK_STATE_SHIFT, 126 SCX_TASK_ENABLED = 4 << SCX_TASK_STATE_SHIFT, 127 SCX_TASK_DEAD = 5 << SCX_TASK_STATE_SHIFT, 128 129 /* 130 * Bits 12 to 14 are used to carry reenqueue reason. In addition to 131 * %SCX_ENQ_REENQ flag, ops.enqueue() can also test for 132 * %SCX_TASK_REENQ_REASON_NONE to distinguish reenqueues. 133 * 134 * NONE not being reenqueued 135 * KFUNC reenqueued by scx_bpf_dsq_reenq() and friends 136 * IMMED reenqueued due to failed ENQ_IMMED 137 * PREEMPTED preempted while running 138 * CAP sub-sched cap miss, see p->scx.reenq_reason_* 139 */ 140 SCX_TASK_REENQ_REASON_SHIFT = 12, 141 SCX_TASK_REENQ_REASON_BITS = 3, 142 SCX_TASK_REENQ_REASON_MASK = ((1 << SCX_TASK_REENQ_REASON_BITS) - 1) << SCX_TASK_REENQ_REASON_SHIFT, 143 144 SCX_TASK_REENQ_NONE = 0 << SCX_TASK_REENQ_REASON_SHIFT, 145 SCX_TASK_REENQ_KFUNC = 1 << SCX_TASK_REENQ_REASON_SHIFT, 146 SCX_TASK_REENQ_IMMED = 2 << SCX_TASK_REENQ_REASON_SHIFT, 147 SCX_TASK_REENQ_PREEMPTED = 3 << SCX_TASK_REENQ_REASON_SHIFT, 148 SCX_TASK_REENQ_CAP = 4 << SCX_TASK_REENQ_REASON_SHIFT, 149 150 /* iteration cursor, not a task */ 151 SCX_TASK_CURSOR = 1 << 31, 152 }; 153 154 /* scx_entity.dsq_flags */ 155 enum scx_ent_dsq_flags { 156 SCX_TASK_DSQ_ON_PRIQ = 1 << 0, /* task is queued on the priority queue of a dsq */ 157 }; 158 159 enum scx_dsq_lnode_flags { 160 SCX_DSQ_LNODE_ITER_CURSOR = 1 << 0, 161 162 /* high 16 bits can be for iter cursor flags */ 163 __SCX_DSQ_LNODE_PRIV_SHIFT = 16, 164 }; 165 166 struct scx_dsq_list_node { 167 struct list_head node; 168 u32 flags; 169 u32 priv; /* can be used by iter cursor */ 170 }; 171 172 #define INIT_DSQ_LIST_CURSOR(__cursor, __dsq, __flags) \ 173 (struct scx_dsq_list_node) { \ 174 .node = LIST_HEAD_INIT((__cursor).node), \ 175 .flags = SCX_DSQ_LNODE_ITER_CURSOR | (__flags), \ 176 .priv = READ_ONCE((__dsq)->seq), \ 177 } 178 179 struct scx_sched; 180 181 /* 182 * The following is embedded in task_struct and contains all fields necessary 183 * for a task to be scheduled by SCX. 184 */ 185 struct sched_ext_entity { 186 #ifdef CONFIG_CGROUPS 187 /* 188 * Associated scx_sched. Updated either during fork or while holding 189 * both p->pi_lock and rq lock. 190 */ 191 struct scx_sched __rcu *sched; 192 #endif 193 struct scx_dispatch_q *dsq; 194 atomic_long_t ops_state; 195 u64 ddsp_dsq_id; 196 u64 ddsp_enq_flags; 197 u64 ddsp_slice; 198 u64 ddsp_vtime; 199 struct scx_dsq_list_node dsq_list; /* dispatch order */ 200 struct rb_node dsq_priq; /* p->scx.dsq_vtime order */ 201 u32 dsq_seq; 202 u32 dsq_flags; /* protected by DSQ lock */ 203 u32 flags; /* protected by rq lock */ 204 u32 weight; 205 u32 reenq_cnt; /* reenqueues since last run */ 206 s32 sticky_cpu; 207 s32 holding_cpu; 208 s32 selected_cpu; 209 s32 runnable_cpu; /* cpu @p is runnable on, -1 if not */ 210 u32 ops_qseq; /* protected by rq lock */ 211 struct task_struct *kf_tasks[2]; /* see SCX_CALL_OP_TASK() */ 212 213 struct list_head runnable_node; /* rq->scx.runnable_list */ 214 unsigned long runnable_at; 215 216 #ifdef CONFIG_EXT_SUB_SCHED 217 unsigned long rescue_at; /* queued on a rescue DSQ at, jiffies */ 218 #endif 219 220 /* 221 * Unique non-zero task ID assigned at fork. Persists across exec and 222 * is never reused. Lets BPF schedulers identify tasks without storing 223 * kernel pointers - arena-backed schedulers being one example. See 224 * scx_bpf_tid_to_task(). 225 */ 226 u64 tid; 227 struct rhash_head tid_hash_node; /* see SCX_OPS_TID_TO_TASK */ 228 229 /* BPF scheduler modifiable fields */ 230 231 /* 232 * Runtime budget in nsecs - how long the task may hold its cpu. Owned 233 * by the task's scheduler. Set it when enqueuing via 234 * scx_bpf_dsq_insert(), or otherwise via scx_bpf_task_set_slice(). 235 * Automatically decreased as the task executes. On depletion a 236 * scheduling event is triggered. 237 * 238 * This value is cleared to zero if the task is preempted by 239 * %SCX_KICK_PREEMPT and shouldn't be used to determine how long the 240 * task ran. Use p->se.sum_exec_runtime instead. 241 */ 242 u64 slice; 243 244 /* 245 * Used to order tasks when dispatching to the vtime-ordered priority 246 * queue of a dsq. This is usually set through 247 * scx_bpf_dsq_insert_vtime() but can also be modified directly by the 248 * BPF scheduler. Modifying it while a task is queued on a dsq may 249 * mangle the ordering and is not recommended. 250 */ 251 u64 dsq_vtime; 252 253 /* 254 * Out-of-band slice request from scx_bpf_task_set_slice() when the 255 * caller does not hold the rq lock, applied under the rq lock at the 256 * next slice consideration. One atomic64 packs the pending flag, the 257 * issuing sch's id, and the requested slice. See scx_slice_oob_consts. 258 */ 259 atomic64_t slice_oob; 260 261 /* 262 * Sub-sched cap rejected reenq context, valid only while 263 * %SCX_TASK_REENQ_CAP is set. @reenq_reason_caps is the SCX_CAP_* bits 264 * that were needed but missing. @reenq_reason_cid is the target cid. 265 */ 266 u64 reenq_reason_caps; 267 s32 reenq_reason_cid; 268 269 /* 270 * If set, reject future sched_setscheduler(2) calls updating the policy 271 * to %SCHED_EXT with -%EACCES. 272 * 273 * Can be set from ops.init_task() while the BPF scheduler is being 274 * loaded. If set and the task's policy is already %SCHED_EXT, the 275 * task's policy is rejected and forcefully reverted to %SCHED_NORMAL. 276 * The number of such events are reported through 277 * /sys/kernel/sched_ext/nr_rejected. Setting this flag from any other 278 * ops.init_task() invocation, such as during fork, fails the scheduler. 279 */ 280 bool disallow; /* reject switching into SCX */ 281 282 /* cold fields */ 283 #ifdef CONFIG_EXT_GROUP_SCHED 284 struct cgroup *cgrp_moving_from; 285 #endif 286 struct list_head tasks_node; 287 }; 288 289 void sched_ext_dead(struct task_struct *p); 290 void print_scx_info(const char *log_lvl, struct task_struct *p); 291 void scx_softlockup(u32 dur_s); 292 bool scx_hardlockup(int cpu); 293 bool scx_rcu_cpu_stall(const struct cpumask *stalled_mask); 294 295 #else /* !CONFIG_SCHED_CLASS_EXT */ 296 297 static inline void sched_ext_dead(struct task_struct *p) {} 298 static inline void print_scx_info(const char *log_lvl, struct task_struct *p) {} 299 static inline void scx_softlockup(u32 dur_s) {} 300 static inline bool scx_hardlockup(int cpu) { return false; } 301 static inline bool scx_rcu_cpu_stall(const struct cpumask *stalled_mask) { return false; } 302 303 #endif /* CONFIG_SCHED_CLASS_EXT */ 304 305 struct scx_task_group { 306 #ifdef CONFIG_EXT_GROUP_SCHED 307 /* 308 * The sched this tg is on, NULL if none. SCX_TG_INITED tracks whether 309 * ops.cgroup_init() succeeded on it. When a child sched exits and its 310 * tgs move to the parent, a failed init leaves the tg on the parent 311 * with INITED clear (see scx_cgroup_return_subtree()). 312 * 313 * This is tracked separately from cgrp->scx_sched because the tg 314 * hierarchy can diverge from the cgroup2 hierarchy in both lifetime and 315 * shape. A tg stays online past its cgroup's removal while the 316 * cgrp->scx_sched rewrites visit only live cgroups, leaving a removed 317 * cgroup's pointer stale. The cpu controller can also be mounted on 318 * cgroup1. 319 */ 320 struct scx_sched *sched; 321 322 u32 flags; /* SCX_TG_* */ 323 u32 weight; 324 u64 bw_period_us; 325 u64 bw_quota_us; 326 u64 bw_burst_us; 327 bool idle; 328 #endif 329 }; 330 331 #endif /* _LINUX_SCHED_EXT_H */ 332