Linux Audio

Check our new training course

Embedded Linux Audio

Check our new training course
with Creative Commons CC-BY-SA
lecture materials

Bootlin logo

Elixir Cross Referencer

Loading...
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
// SPDX-License-Identifier: GPL-2.0
/* cpumap.c: used for optimizing CPU assignment
 *
 * Copyright (C) 2009 Hong H. Pham <hong.pham@windriver.com>
 */

#include <linux/export.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/cpumask.h>
#include <linux/spinlock.h>
#include <asm/cpudata.h>
#include "cpumap.h"


enum {
	CPUINFO_LVL_ROOT = 0,
	CPUINFO_LVL_NODE,
	CPUINFO_LVL_CORE,
	CPUINFO_LVL_PROC,
	CPUINFO_LVL_MAX,
};

enum {
	ROVER_NO_OP              = 0,
	/* Increment rover every time level is visited */
	ROVER_INC_ON_VISIT       = 1 << 0,
	/* Increment parent's rover every time rover wraps around */
	ROVER_INC_PARENT_ON_LOOP = 1 << 1,
};

struct cpuinfo_node {
	int id;
	int level;
	int num_cpus;    /* Number of CPUs in this hierarchy */
	int parent_index;
	int child_start; /* Array index of the first child node */
	int child_end;   /* Array index of the last child node */
	int rover;       /* Child node iterator */
};

struct cpuinfo_level {
	int start_index; /* Index of first node of a level in a cpuinfo tree */
	int end_index;   /* Index of last node of a level in a cpuinfo tree */
	int num_nodes;   /* Number of nodes in a level in a cpuinfo tree */
};

struct cpuinfo_tree {
	int total_nodes;

	/* Offsets into nodes[] for each level of the tree */
	struct cpuinfo_level level[CPUINFO_LVL_MAX];
	struct cpuinfo_node  nodes[0];
};


static struct cpuinfo_tree *cpuinfo_tree;

static u16 cpu_distribution_map[NR_CPUS];
static DEFINE_SPINLOCK(cpu_map_lock);


/* Niagara optimized cpuinfo tree traversal. */
static const int niagara_iterate_method[] = {
	[CPUINFO_LVL_ROOT] = ROVER_NO_OP,

	/* Strands (or virtual CPUs) within a core may not run concurrently
	 * on the Niagara, as instruction pipeline(s) are shared.  Distribute
	 * work to strands in different cores first for better concurrency.
	 * Go to next NUMA node when all cores are used.
	 */
	[CPUINFO_LVL_NODE] = ROVER_INC_ON_VISIT|ROVER_INC_PARENT_ON_LOOP,

	/* Strands are grouped together by proc_id in cpuinfo_sparc, i.e.
	 * a proc_id represents an instruction pipeline.  Distribute work to
	 * strands in different proc_id groups if the core has multiple
	 * instruction pipelines (e.g. the Niagara 2/2+ has two).
	 */
	[CPUINFO_LVL_CORE] = ROVER_INC_ON_VISIT,

	/* Pick the next strand in the proc_id group. */
	[CPUINFO_LVL_PROC] = ROVER_INC_ON_VISIT,
};

/* Generic cpuinfo tree traversal.  Distribute work round robin across NUMA
 * nodes.
 */
static const int generic_iterate_method[] = {
	[CPUINFO_LVL_ROOT] = ROVER_INC_ON_VISIT,
	[CPUINFO_LVL_NODE] = ROVER_NO_OP,
	[CPUINFO_LVL_CORE] = ROVER_INC_PARENT_ON_LOOP,
	[CPUINFO_LVL_PROC] = ROVER_INC_ON_VISIT|ROVER_INC_PARENT_ON_LOOP,
};


static int cpuinfo_id(int cpu, int level)
{
	int id;

	switch (level) {
	case CPUINFO_LVL_ROOT:
		id = 0;
		break;
	case CPUINFO_LVL_NODE:
		id = cpu_to_node(cpu);
		break;
	case CPUINFO_LVL_CORE:
		id = cpu_data(cpu).core_id;
		break;
	case CPUINFO_LVL_PROC:
		id = cpu_data(cpu).proc_id;
		break;
	default:
		id = -EINVAL;
	}
	return id;
}

/*
 * Enumerate the CPU information in __cpu_data to determine the start index,
 * end index, and number of nodes for each level in the cpuinfo tree.  The
 * total number of cpuinfo nodes required to build the tree is returned.
 */
static int enumerate_cpuinfo_nodes(struct cpuinfo_level *tree_level)
{
	int prev_id[CPUINFO_LVL_MAX];
	int i, n, num_nodes;

	for (i = CPUINFO_LVL_ROOT; i < CPUINFO_LVL_MAX; i++) {
		struct cpuinfo_level *lv = &tree_level[i];

		prev_id[i] = -1;
		lv->start_index = lv->end_index = lv->num_nodes = 0;
	}

	num_nodes = 1; /* Include the root node */

	for (i = 0; i < num_possible_cpus(); i++) {
		if (!cpu_online(i))
			continue;

		n = cpuinfo_id(i, CPUINFO_LVL_NODE);
		if (n > prev_id[CPUINFO_LVL_NODE]) {
			tree_level[CPUINFO_LVL_NODE].num_nodes++;
			prev_id[CPUINFO_LVL_NODE] = n;
			num_nodes++;
		}
		n = cpuinfo_id(i, CPUINFO_LVL_CORE);
		if (n > prev_id[CPUINFO_LVL_CORE]) {
			tree_level[CPUINFO_LVL_CORE].num_nodes++;
			prev_id[CPUINFO_LVL_CORE] = n;
			num_nodes++;
		}
		n = cpuinfo_id(i, CPUINFO_LVL_PROC);
		if (n > prev_id[CPUINFO_LVL_PROC]) {
			tree_level[CPUINFO_LVL_PROC].num_nodes++;
			prev_id[CPUINFO_LVL_PROC] = n;
			num_nodes++;
		}
	}

	tree_level[CPUINFO_LVL_ROOT].num_nodes = 1;

	n = tree_level[CPUINFO_LVL_NODE].num_nodes;
	tree_level[CPUINFO_LVL_NODE].start_index = 1;
	tree_level[CPUINFO_LVL_NODE].end_index   = n;

	n++;
	tree_level[CPUINFO_LVL_CORE].start_index = n;
	n += tree_level[CPUINFO_LVL_CORE].num_nodes;
	tree_level[CPUINFO_LVL_CORE].end_index   = n - 1;

	tree_level[CPUINFO_LVL_PROC].start_index = n;
	n += tree_level[CPUINFO_LVL_PROC].num_nodes;
	tree_level[CPUINFO_LVL_PROC].end_index   = n - 1;

	return num_nodes;
}

/* Build a tree representation of the CPU hierarchy using the per CPU
 * information in __cpu_data.  Entries in __cpu_data[0..NR_CPUS] are
 * assumed to be sorted in ascending order based on node, core_id, and
 * proc_id (in order of significance).
 */
static struct cpuinfo_tree *build_cpuinfo_tree(void)
{
	struct cpuinfo_tree *new_tree;
	struct cpuinfo_node *node;
	struct cpuinfo_level tmp_level[CPUINFO_LVL_MAX];
	int num_cpus[CPUINFO_LVL_MAX];
	int level_rover[CPUINFO_LVL_MAX];
	int prev_id[CPUINFO_LVL_MAX];
	int n, id, cpu, prev_cpu, last_cpu, level;

	n = enumerate_cpuinfo_nodes(tmp_level);

	new_tree = kzalloc(struct_size(new_tree, nodes, n), GFP_ATOMIC);
	if (!new_tree)
		return NULL;

	new_tree->total_nodes = n;
	memcpy(&new_tree->level, tmp_level, sizeof(tmp_level));

	prev_cpu = cpu = cpumask_first(cpu_online_mask);

	/* Initialize all levels in the tree with the first CPU */
	for (level = CPUINFO_LVL_PROC; level >= CPUINFO_LVL_ROOT; level--) {
		n = new_tree->level[level].start_index;

		level_rover[level] = n;
		node = &new_tree->nodes[n];

		id = cpuinfo_id(cpu, level);
		if (unlikely(id < 0)) {
			kfree(new_tree);
			return NULL;
		}
		node->id = id;
		node->level = level;
		node->num_cpus = 1;

		node->parent_index = (level > CPUINFO_LVL_ROOT)
		    ? new_tree->level[level - 1].start_index : -1;

		node->child_start = node->child_end = node->rover =
		    (level == CPUINFO_LVL_PROC)
		    ? cpu : new_tree->level[level + 1].start_index;

		prev_id[level] = node->id;
		num_cpus[level] = 1;
	}

	for (last_cpu = (num_possible_cpus() - 1); last_cpu >= 0; last_cpu--) {
		if (cpu_online(last_cpu))
			break;
	}

	while (++cpu <= last_cpu) {
		if (!cpu_online(cpu))
			continue;

		for (level = CPUINFO_LVL_PROC; level >= CPUINFO_LVL_ROOT;
		     level--) {
			id = cpuinfo_id(cpu, level);
			if (unlikely(id < 0)) {
				kfree(new_tree);
				return NULL;
			}

			if ((id != prev_id[level]) || (cpu == last_cpu)) {
				prev_id[level] = id;
				node = &new_tree->nodes[level_rover[level]];
				node->num_cpus = num_cpus[level];
				num_cpus[level] = 1;

				if (cpu == last_cpu)
					node->num_cpus++;

				/* Connect tree node to parent */
				if (level == CPUINFO_LVL_ROOT)
					node->parent_index = -1;
				else
					node->parent_index =
					    level_rover[level - 1];

				if (level == CPUINFO_LVL_PROC) {
					node->child_end =
					    (cpu == last_cpu) ? cpu : prev_cpu;
				} else {
					node->child_end =
					    level_rover[level + 1] - 1;
				}

				/* Initialize the next node in the same level */
				n = ++level_rover[level];
				if (n <= new_tree->level[level].end_index) {
					node = &new_tree->nodes[n];
					node->id = id;
					node->level = level;

					/* Connect node to child */
					node->child_start = node->child_end =
					node->rover =
					    (level == CPUINFO_LVL_PROC)
					    ? cpu : level_rover[level + 1];
				}
			} else
				num_cpus[level]++;
		}
		prev_cpu = cpu;
	}

	return new_tree;
}

static void increment_rover(struct cpuinfo_tree *t, int node_index,
                            int root_index, const int *rover_inc_table)
{
	struct cpuinfo_node *node = &t->nodes[node_index];
	int top_level, level;

	top_level = t->nodes[root_index].level;
	for (level = node->level; level >= top_level; level--) {
		node->rover++;
		if (node->rover <= node->child_end)
			return;

		node->rover = node->child_start;
		/* If parent's rover does not need to be adjusted, stop here. */
		if ((level == top_level) ||
		    !(rover_inc_table[level] & ROVER_INC_PARENT_ON_LOOP))
			return;

		node = &t->nodes[node->parent_index];
	}
}

static int iterate_cpu(struct cpuinfo_tree *t, unsigned int root_index)
{
	const int *rover_inc_table;
	int level, new_index, index = root_index;

	switch (sun4v_chip_type) {
	case SUN4V_CHIP_NIAGARA1:
	case SUN4V_CHIP_NIAGARA2:
	case SUN4V_CHIP_NIAGARA3:
	case SUN4V_CHIP_NIAGARA4:
	case SUN4V_CHIP_NIAGARA5:
	case SUN4V_CHIP_SPARC_M6:
	case SUN4V_CHIP_SPARC_M7:
	case SUN4V_CHIP_SPARC_M8:
	case SUN4V_CHIP_SPARC_SN:
	case SUN4V_CHIP_SPARC64X:
		rover_inc_table = niagara_iterate_method;
		break;
	default:
		rover_inc_table = generic_iterate_method;
	}

	for (level = t->nodes[root_index].level; level < CPUINFO_LVL_MAX;
	     level++) {
		new_index = t->nodes[index].rover;
		if (rover_inc_table[level] & ROVER_INC_ON_VISIT)
			increment_rover(t, index, root_index, rover_inc_table);

		index = new_index;
	}
	return index;
}

static void _cpu_map_rebuild(void)
{
	int i;

	if (cpuinfo_tree) {
		kfree(cpuinfo_tree);
		cpuinfo_tree = NULL;
	}

	cpuinfo_tree = build_cpuinfo_tree();
	if (!cpuinfo_tree)
		return;

	/* Build CPU distribution map that spans all online CPUs.  No need
	 * to check if the CPU is online, as that is done when the cpuinfo
	 * tree is being built.
	 */
	for (i = 0; i < cpuinfo_tree->nodes[0].num_cpus; i++)
		cpu_distribution_map[i] = iterate_cpu(cpuinfo_tree, 0);
}

/* Fallback if the cpuinfo tree could not be built.  CPU mapping is linear
 * round robin.
 */
static int simple_map_to_cpu(unsigned int index)
{
	int i, end, cpu_rover;

	cpu_rover = 0;
	end = index % num_online_cpus();
	for (i = 0; i < num_possible_cpus(); i++) {
		if (cpu_online(cpu_rover)) {
			if (cpu_rover >= end)
				return cpu_rover;

			cpu_rover++;
		}
	}

	/* Impossible, since num_online_cpus() <= num_possible_cpus() */
	return cpumask_first(cpu_online_mask);
}

static int _map_to_cpu(unsigned int index)
{
	struct cpuinfo_node *root_node;

	if (unlikely(!cpuinfo_tree)) {
		_cpu_map_rebuild();
		if (!cpuinfo_tree)
			return simple_map_to_cpu(index);
	}

	root_node = &cpuinfo_tree->nodes[0];
#ifdef CONFIG_HOTPLUG_CPU
	if (unlikely(root_node->num_cpus != num_online_cpus())) {
		_cpu_map_rebuild();
		if (!cpuinfo_tree)
			return simple_map_to_cpu(index);
	}
#endif
	return cpu_distribution_map[index % root_node->num_cpus];
}

int map_to_cpu(unsigned int index)
{
	int mapped_cpu;
	unsigned long flag;

	spin_lock_irqsave(&cpu_map_lock, flag);
	mapped_cpu = _map_to_cpu(index);

#ifdef CONFIG_HOTPLUG_CPU
	while (unlikely(!cpu_online(mapped_cpu)))
		mapped_cpu = _map_to_cpu(index);
#endif
	spin_unlock_irqrestore(&cpu_map_lock, flag);
	return mapped_cpu;
}
EXPORT_SYMBOL(map_to_cpu);

void cpu_map_rebuild(void)
{
	unsigned long flag;

	spin_lock_irqsave(&cpu_map_lock, flag);
	_cpu_map_rebuild();
	spin_unlock_irqrestore(&cpu_map_lock, flag);
}