cpudeadline.c

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