kernel/sched/cpudeadline.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  *  kernel/sched/cpudeadline.c
0004  *
0005  *  Global CPU deadline management
0006  *
0007  *  Author: Juri Lelli <j.lelli@sssup.it>
0008  */
0009
0010 static inline int parent(int i)
0011 {
0012     return (i - 1) >> 1;
0013 }
0014
0015 static inline int left_child(int i)
0016 {
0017     return (i << 1) + 1;
0018 }
0019
0020 static inline int right_child(int i)
0021 {
0022     return (i << 1) + 2;
0023 }
0024
0025 static void cpudl_heapify_down(struct cpudl *cp, int idx)
0026 {
0027     int l, r, largest;
0028
0029     int orig_cpu = cp->elements[idx].cpu;
0030     u64 orig_dl = cp->elements[idx].dl;
0031
0032     if (left_child(idx) >= cp->size)
0033         return;
0034
0035     /* adapted from lib/prio_heap.c */
0036     while (1) {
0037         u64 largest_dl;
0038
0039         l = left_child(idx);
0040         r = right_child(idx);
0041         largest = idx;
0042         largest_dl = orig_dl;
0043
0044         if ((l < cp->size) && dl_time_before(orig_dl,
0045                         cp->elements[l].dl)) {
0046             largest = l;
0047             largest_dl = cp->elements[l].dl;
0048         }
0049         if ((r < cp->size) && dl_time_before(largest_dl,
0050                         cp->elements[r].dl))
0051             largest = r;
0052
0053         if (largest == idx)
0054             break;
0055
0056         /* pull largest child onto idx */
0057         cp->elements[idx].cpu = cp->elements[largest].cpu;
0058         cp->elements[idx].dl = cp->elements[largest].dl;
0059         cp->elements[cp->elements[idx].cpu].idx = idx;
0060         idx = largest;
0061     }
0062     /* actual push down of saved original values orig_* */
0063     cp->elements[idx].cpu = orig_cpu;
0064     cp->elements[idx].dl = orig_dl;
0065     cp->elements[cp->elements[idx].cpu].idx = idx;
0066 }
0067
0068 static void cpudl_heapify_up(struct cpudl *cp, int idx)
0069 {
0070     int p;
0071
0072     int orig_cpu = cp->elements[idx].cpu;
0073     u64 orig_dl = cp->elements[idx].dl;
0074
0075     if (idx == 0)
0076         return;
0077
0078     do {
0079         p = parent(idx);
0080         if (dl_time_before(orig_dl, cp->elements[p].dl))
0081             break;
0082         /* pull parent onto idx */
0083         cp->elements[idx].cpu = cp->elements[p].cpu;
0084         cp->elements[idx].dl = cp->elements[p].dl;
0085         cp->elements[cp->elements[idx].cpu].idx = idx;
0086         idx = p;
0087     } while (idx != 0);
0088     /* actual push up of saved original values orig_* */
0089     cp->elements[idx].cpu = orig_cpu;
0090     cp->elements[idx].dl = orig_dl;
0091     cp->elements[cp->elements[idx].cpu].idx = idx;
0092 }
0093
0094 static void cpudl_heapify(struct cpudl *cp, int idx)
0095 {
0096     if (idx > 0 && dl_time_before(cp->elements[parent(idx)].dl,
0097                 cp->elements[idx].dl))
0098         cpudl_heapify_up(cp, idx);
0099     else
0100         cpudl_heapify_down(cp, idx);
0101 }
0102
0103 static inline int cpudl_maximum(struct cpudl *cp)
0104 {
0105     return cp->elements[0].cpu;
0106 }
0107
0108 /*
0109  * cpudl_find - find the best (later-dl) CPU in the system
0110  * @cp: the cpudl max-heap context
0111  * @p: the task
0112  * @later_mask: a mask to fill in with the selected CPUs (or NULL)
0113  *
0114  * Returns: int - CPUs were found
0115  */
0116 int cpudl_find(struct cpudl *cp, struct task_struct *p,
0117            struct cpumask *later_mask)
0118 {
0119     const struct sched_dl_entity *dl_se = &p->dl;
0120
0121     if (later_mask &&
0122         cpumask_and(later_mask, cp->free_cpus, &p->cpus_mask)) {
0123         unsigned long cap, max_cap = 0;
0124         int cpu, max_cpu = -1;
0125
0126         if (!static_branch_unlikely(&sched_asym_cpucapacity))
0127             return 1;
0128
0129         /* Ensure the capacity of the CPUs fits the task. */
0130         for_each_cpu(cpu, later_mask) {
0131             if (!dl_task_fits_capacity(p, cpu)) {
0132                 cpumask_clear_cpu(cpu, later_mask);
0133
0134                 cap = capacity_orig_of(cpu);
0135
0136                 if (cap > max_cap ||
0137                     (cpu == task_cpu(p) && cap == max_cap)) {
0138                     max_cap = cap;
0139                     max_cpu = cpu;
0140                 }
0141             }
0142         }
0143
0144         if (cpumask_empty(later_mask))
0145             cpumask_set_cpu(max_cpu, later_mask);
0146
0147         return 1;
0148     } else {
0149         int best_cpu = cpudl_maximum(cp);
0150
0151         WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
0152
0153         if (cpumask_test_cpu(best_cpu, &p->cpus_mask) &&
0154             dl_time_before(dl_se->deadline, cp->elements[0].dl)) {
0155             if (later_mask)
0156                 cpumask_set_cpu(best_cpu, later_mask);
0157
0158             return 1;
0159         }
0160     }
0161     return 0;
0162 }
0163
0164 /*
0165  * cpudl_clear - remove a CPU from the cpudl max-heap
0166  * @cp: the cpudl max-heap context
0167  * @cpu: the target CPU
0168  *
0169  * Notes: assumes cpu_rq(cpu)->lock is locked
0170  *
0171  * Returns: (void)
0172  */
0173 void cpudl_clear(struct cpudl *cp, int cpu)
0174 {
0175     int old_idx, new_cpu;
0176     unsigned long flags;
0177
0178     WARN_ON(!cpu_present(cpu));
0179
0180     raw_spin_lock_irqsave(&cp->lock, flags);
0181
0182     old_idx = cp->elements[cpu].idx;
0183     if (old_idx == IDX_INVALID) {
0184         /*
0185          * Nothing to remove if old_idx was invalid.
0186          * This could happen if a rq_offline_dl is
0187          * called for a CPU without -dl tasks running.
0188          */
0189     } else {
0190         new_cpu = cp->elements[cp->size - 1].cpu;
0191         cp->elements[old_idx].dl = cp->elements[cp->size - 1].dl;
0192         cp->elements[old_idx].cpu = new_cpu;
0193         cp->size--;
0194         cp->elements[new_cpu].idx = old_idx;
0195         cp->elements[cpu].idx = IDX_INVALID;
0196         cpudl_heapify(cp, old_idx);
0197
0198         cpumask_set_cpu(cpu, cp->free_cpus);
0199     }
0200     raw_spin_unlock_irqrestore(&cp->lock, flags);
0201 }
0202
0203 /*
0204  * cpudl_set - update the cpudl max-heap
0205  * @cp: the cpudl max-heap context
0206  * @cpu: the target CPU
0207  * @dl: the new earliest deadline for this CPU
0208  *
0209  * Notes: assumes cpu_rq(cpu)->lock is locked
0210  *
0211  * Returns: (void)
0212  */
0213 void cpudl_set(struct cpudl *cp, int cpu, u64 dl)
0214 {
0215     int old_idx;
0216     unsigned long flags;
0217
0218     WARN_ON(!cpu_present(cpu));
0219
0220     raw_spin_lock_irqsave(&cp->lock, flags);
0221
0222     old_idx = cp->elements[cpu].idx;
0223     if (old_idx == IDX_INVALID) {
0224         int new_idx = cp->size++;
0225
0226         cp->elements[new_idx].dl = dl;
0227         cp->elements[new_idx].cpu = cpu;
0228         cp->elements[cpu].idx = new_idx;
0229         cpudl_heapify_up(cp, new_idx);
0230         cpumask_clear_cpu(cpu, cp->free_cpus);
0231     } else {
0232         cp->elements[old_idx].dl = dl;
0233         cpudl_heapify(cp, old_idx);
0234     }
0235
0236     raw_spin_unlock_irqrestore(&cp->lock, flags);
0237 }
0238
0239 /*
0240  * cpudl_set_freecpu - Set the cpudl.free_cpus
0241  * @cp: the cpudl max-heap context
0242  * @cpu: rd attached CPU
0243  */
0244 void cpudl_set_freecpu(struct cpudl *cp, int cpu)
0245 {
0246     cpumask_set_cpu(cpu, cp->free_cpus);
0247 }
0248
0249 /*
0250  * cpudl_clear_freecpu - Clear the cpudl.free_cpus
0251  * @cp: the cpudl max-heap context
0252  * @cpu: rd attached CPU
0253  */
0254 void cpudl_clear_freecpu(struct cpudl *cp, int cpu)
0255 {
0256     cpumask_clear_cpu(cpu, cp->free_cpus);
0257 }
0258
0259 /*
0260  * cpudl_init - initialize the cpudl structure
0261  * @cp: the cpudl max-heap context
0262  */
0263 int cpudl_init(struct cpudl *cp)
0264 {
0265     int i;
0266
0267     raw_spin_lock_init(&cp->lock);
0268     cp->size = 0;
0269
0270     cp->elements = kcalloc(nr_cpu_ids,
0271                    sizeof(struct cpudl_item),
0272                    GFP_KERNEL);
0273     if (!cp->elements)
0274         return -ENOMEM;
0275
0276     if (!zalloc_cpumask_var(&cp->free_cpus, GFP_KERNEL)) {
0277         kfree(cp->elements);
0278         return -ENOMEM;
0279     }
0280
0281     for_each_possible_cpu(i)
0282         cp->elements[i].idx = IDX_INVALID;
0283
0284     return 0;
0285 }
0286
0287 /*
0288  * cpudl_cleanup - clean up the cpudl structure
0289  * @cp: the cpudl max-heap context
0290  */
0291 void cpudl_cleanup(struct cpudl *cp)
0292 {
0293     free_cpumask_var(cp->free_cpus);
0294     kfree(cp->elements);
0295 }