xref: /openbmc/linux/kernel/sched/cpudeadline.c (revision 740cf8a7)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  kernel/sched/cpudeadline.c
4  *
5  *  Global CPU deadline management
6  *
7  *  Author: Juri Lelli <j.lelli@sssup.it>
8  */
9 
parent(int i)10 static inline int parent(int i)
11 {
12 	return (i - 1) >> 1;
13 }
14 
left_child(int i)15 static inline int left_child(int i)
16 {
17 	return (i << 1) + 1;
18 }
19 
right_child(int i)20 static inline int right_child(int i)
21 {
22 	return (i << 1) + 2;
23 }
24 
cpudl_heapify_down(struct cpudl * cp,int idx)25 static void cpudl_heapify_down(struct cpudl *cp, int idx)
26 {
27 	int l, r, largest;
28 
29 	int orig_cpu = cp->elements[idx].cpu;
30 	u64 orig_dl = cp->elements[idx].dl;
31 
32 	if (left_child(idx) >= cp->size)
33 		return;
34 
35 	/* adapted from lib/prio_heap.c */
36 	while (1) {
37 		u64 largest_dl;
38 
39 		l = left_child(idx);
40 		r = right_child(idx);
41 		largest = idx;
42 		largest_dl = orig_dl;
43 
44 		if ((l < cp->size) && dl_time_before(orig_dl,
45 						cp->elements[l].dl)) {
46 			largest = l;
47 			largest_dl = cp->elements[l].dl;
48 		}
49 		if ((r < cp->size) && dl_time_before(largest_dl,
50 						cp->elements[r].dl))
51 			largest = r;
52 
53 		if (largest == idx)
54 			break;
55 
56 		/* pull largest child onto idx */
57 		cp->elements[idx].cpu = cp->elements[largest].cpu;
58 		cp->elements[idx].dl = cp->elements[largest].dl;
59 		cp->elements[cp->elements[idx].cpu].idx = idx;
60 		idx = largest;
61 	}
62 	/* actual push down of saved original values orig_* */
63 	cp->elements[idx].cpu = orig_cpu;
64 	cp->elements[idx].dl = orig_dl;
65 	cp->elements[cp->elements[idx].cpu].idx = idx;
66 }
67 
cpudl_heapify_up(struct cpudl * cp,int idx)68 static void cpudl_heapify_up(struct cpudl *cp, int idx)
69 {
70 	int p;
71 
72 	int orig_cpu = cp->elements[idx].cpu;
73 	u64 orig_dl = cp->elements[idx].dl;
74 
75 	if (idx == 0)
76 		return;
77 
78 	do {
79 		p = parent(idx);
80 		if (dl_time_before(orig_dl, cp->elements[p].dl))
81 			break;
82 		/* pull parent onto idx */
83 		cp->elements[idx].cpu = cp->elements[p].cpu;
84 		cp->elements[idx].dl = cp->elements[p].dl;
85 		cp->elements[cp->elements[idx].cpu].idx = idx;
86 		idx = p;
87 	} while (idx != 0);
88 	/* actual push up of saved original values orig_* */
89 	cp->elements[idx].cpu = orig_cpu;
90 	cp->elements[idx].dl = orig_dl;
91 	cp->elements[cp->elements[idx].cpu].idx = idx;
92 }
93 
cpudl_heapify(struct cpudl * cp,int idx)94 static void cpudl_heapify(struct cpudl *cp, int idx)
95 {
96 	if (idx > 0 && dl_time_before(cp->elements[parent(idx)].dl,
97 				cp->elements[idx].dl))
98 		cpudl_heapify_up(cp, idx);
99 	else
100 		cpudl_heapify_down(cp, idx);
101 }
102 
cpudl_maximum(struct cpudl * cp)103 static inline int cpudl_maximum(struct cpudl *cp)
104 {
105 	return cp->elements[0].cpu;
106 }
107 
108 /*
109  * cpudl_find - find the best (later-dl) CPU in the system
110  * @cp: the cpudl max-heap context
111  * @p: the task
112  * @later_mask: a mask to fill in with the selected CPUs (or NULL)
113  *
114  * Returns: int - CPUs were found
115  */
cpudl_find(struct cpudl * cp,struct task_struct * p,struct cpumask * later_mask)116 int cpudl_find(struct cpudl *cp, struct task_struct *p,
117 	       struct cpumask *later_mask)
118 {
119 	const struct sched_dl_entity *dl_se = &p->dl;
120 
121 	if (later_mask &&
122 	    cpumask_and(later_mask, cp->free_cpus, &p->cpus_mask)) {
123 		unsigned long cap, max_cap = 0;
124 		int cpu, max_cpu = -1;
125 
126 		if (!sched_asym_cpucap_active())
127 			return 1;
128 
129 		/* Ensure the capacity of the CPUs fits the task. */
130 		for_each_cpu(cpu, later_mask) {
131 			if (!dl_task_fits_capacity(p, cpu)) {
132 				cpumask_clear_cpu(cpu, later_mask);
133 
134 				cap = capacity_orig_of(cpu);
135 
136 				if (cap > max_cap ||
137 				    (cpu == task_cpu(p) && cap == max_cap)) {
138 					max_cap = cap;
139 					max_cpu = cpu;
140 				}
141 			}
142 		}
143 
144 		if (cpumask_empty(later_mask))
145 			cpumask_set_cpu(max_cpu, later_mask);
146 
147 		return 1;
148 	} else {
149 		int best_cpu = cpudl_maximum(cp);
150 
151 		WARN_ON(best_cpu != -1 && !cpu_present(best_cpu));
152 
153 		if (cpumask_test_cpu(best_cpu, &p->cpus_mask) &&
154 		    dl_time_before(dl_se->deadline, cp->elements[0].dl)) {
155 			if (later_mask)
156 				cpumask_set_cpu(best_cpu, later_mask);
157 
158 			return 1;
159 		}
160 	}
161 	return 0;
162 }
163 
164 /*
165  * cpudl_clear - remove a CPU from the cpudl max-heap
166  * @cp: the cpudl max-heap context
167  * @cpu: the target CPU
168  *
169  * Notes: assumes cpu_rq(cpu)->lock is locked
170  *
171  * Returns: (void)
172  */
cpudl_clear(struct cpudl * cp,int cpu)173 void cpudl_clear(struct cpudl *cp, int cpu)
174 {
175 	int old_idx, new_cpu;
176 	unsigned long flags;
177 
178 	WARN_ON(!cpu_present(cpu));
179 
180 	raw_spin_lock_irqsave(&cp->lock, flags);
181 
182 	old_idx = cp->elements[cpu].idx;
183 	if (old_idx == IDX_INVALID) {
184 		/*
185 		 * Nothing to remove if old_idx was invalid.
186 		 * This could happen if a rq_offline_dl is
187 		 * called for a CPU without -dl tasks running.
188 		 */
189 	} else {
190 		new_cpu = cp->elements[cp->size - 1].cpu;
191 		cp->elements[old_idx].dl = cp->elements[cp->size - 1].dl;
192 		cp->elements[old_idx].cpu = new_cpu;
193 		cp->size--;
194 		cp->elements[new_cpu].idx = old_idx;
195 		cp->elements[cpu].idx = IDX_INVALID;
196 		cpudl_heapify(cp, old_idx);
197 
198 		cpumask_set_cpu(cpu, cp->free_cpus);
199 	}
200 	raw_spin_unlock_irqrestore(&cp->lock, flags);
201 }
202 
203 /*
204  * cpudl_set - update the cpudl max-heap
205  * @cp: the cpudl max-heap context
206  * @cpu: the target CPU
207  * @dl: the new earliest deadline for this CPU
208  *
209  * Notes: assumes cpu_rq(cpu)->lock is locked
210  *
211  * Returns: (void)
212  */
cpudl_set(struct cpudl * cp,int cpu,u64 dl)213 void cpudl_set(struct cpudl *cp, int cpu, u64 dl)
214 {
215 	int old_idx;
216 	unsigned long flags;
217 
218 	WARN_ON(!cpu_present(cpu));
219 
220 	raw_spin_lock_irqsave(&cp->lock, flags);
221 
222 	old_idx = cp->elements[cpu].idx;
223 	if (old_idx == IDX_INVALID) {
224 		int new_idx = cp->size++;
225 
226 		cp->elements[new_idx].dl = dl;
227 		cp->elements[new_idx].cpu = cpu;
228 		cp->elements[cpu].idx = new_idx;
229 		cpudl_heapify_up(cp, new_idx);
230 		cpumask_clear_cpu(cpu, cp->free_cpus);
231 	} else {
232 		cp->elements[old_idx].dl = dl;
233 		cpudl_heapify(cp, old_idx);
234 	}
235 
236 	raw_spin_unlock_irqrestore(&cp->lock, flags);
237 }
238 
239 /*
240  * cpudl_set_freecpu - Set the cpudl.free_cpus
241  * @cp: the cpudl max-heap context
242  * @cpu: rd attached CPU
243  */
cpudl_set_freecpu(struct cpudl * cp,int cpu)244 void cpudl_set_freecpu(struct cpudl *cp, int cpu)
245 {
246 	cpumask_set_cpu(cpu, cp->free_cpus);
247 }
248 
249 /*
250  * cpudl_clear_freecpu - Clear the cpudl.free_cpus
251  * @cp: the cpudl max-heap context
252  * @cpu: rd attached CPU
253  */
cpudl_clear_freecpu(struct cpudl * cp,int cpu)254 void cpudl_clear_freecpu(struct cpudl *cp, int cpu)
255 {
256 	cpumask_clear_cpu(cpu, cp->free_cpus);
257 }
258 
259 /*
260  * cpudl_init - initialize the cpudl structure
261  * @cp: the cpudl max-heap context
262  */
cpudl_init(struct cpudl * cp)263 int cpudl_init(struct cpudl *cp)
264 {
265 	int i;
266 
267 	raw_spin_lock_init(&cp->lock);
268 	cp->size = 0;
269 
270 	cp->elements = kcalloc(nr_cpu_ids,
271 			       sizeof(struct cpudl_item),
272 			       GFP_KERNEL);
273 	if (!cp->elements)
274 		return -ENOMEM;
275 
276 	if (!zalloc_cpumask_var(&cp->free_cpus, GFP_KERNEL)) {
277 		kfree(cp->elements);
278 		return -ENOMEM;
279 	}
280 
281 	for_each_possible_cpu(i)
282 		cp->elements[i].idx = IDX_INVALID;
283 
284 	return 0;
285 }
286 
287 /*
288  * cpudl_cleanup - clean up the cpudl structure
289  * @cp: the cpudl max-heap context
290  */
cpudl_cleanup(struct cpudl * cp)291 void cpudl_cleanup(struct cpudl *cp)
292 {
293 	free_cpumask_var(cp->free_cpus);
294 	kfree(cp->elements);
295 }
296