1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * mm/percpu-debug.c
4 *
5 * Copyright (C) 2017 Facebook Inc.
6 * Copyright (C) 2017 Dennis Zhou <dennis@kernel.org>
7 *
8 * Prints statistics about the percpu allocator and backing chunks.
9 */
10 #include <linux/debugfs.h>
11 #include <linux/list.h>
12 #include <linux/percpu.h>
13 #include <linux/seq_file.h>
14 #include <linux/sort.h>
15 #include <linux/vmalloc.h>
16
17 #include "percpu-internal.h"
18
19 #define P(X, Y) \
20 seq_printf(m, " %-20s: %12lld\n", X, (long long int)Y)
21
22 struct percpu_stats pcpu_stats;
23 struct pcpu_alloc_info pcpu_stats_ai;
24
cmpint(const void * a,const void * b)25 static int cmpint(const void *a, const void *b)
26 {
27 return *(int *)a - *(int *)b;
28 }
29
30 /*
31 * Iterates over all chunks to find the max nr_alloc entries.
32 */
find_max_nr_alloc(void)33 static int find_max_nr_alloc(void)
34 {
35 struct pcpu_chunk *chunk;
36 int slot, max_nr_alloc;
37 enum pcpu_chunk_type type;
38
39 max_nr_alloc = 0;
40 for (type = 0; type < PCPU_NR_CHUNK_TYPES; type++)
41 for (slot = 0; slot < pcpu_nr_slots; slot++)
42 list_for_each_entry(chunk, &pcpu_chunk_list(type)[slot],
43 list)
44 max_nr_alloc = max(max_nr_alloc,
45 chunk->nr_alloc);
46
47 return max_nr_alloc;
48 }
49
50 /*
51 * Prints out chunk state. Fragmentation is considered between
52 * the beginning of the chunk to the last allocation.
53 *
54 * All statistics are in bytes unless stated otherwise.
55 */
chunk_map_stats(struct seq_file * m,struct pcpu_chunk * chunk,int * buffer)56 static void chunk_map_stats(struct seq_file *m, struct pcpu_chunk *chunk,
57 int *buffer)
58 {
59 struct pcpu_block_md *chunk_md = &chunk->chunk_md;
60 int i, last_alloc, as_len, start, end;
61 int *alloc_sizes, *p;
62 /* statistics */
63 int sum_frag = 0, max_frag = 0;
64 int cur_min_alloc = 0, cur_med_alloc = 0, cur_max_alloc = 0;
65
66 alloc_sizes = buffer;
67
68 /*
69 * find_last_bit returns the start value if nothing found.
70 * Therefore, we must determine if it is a failure of find_last_bit
71 * and set the appropriate value.
72 */
73 last_alloc = find_last_bit(chunk->alloc_map,
74 pcpu_chunk_map_bits(chunk) -
75 chunk->end_offset / PCPU_MIN_ALLOC_SIZE - 1);
76 last_alloc = test_bit(last_alloc, chunk->alloc_map) ?
77 last_alloc + 1 : 0;
78
79 as_len = 0;
80 start = chunk->start_offset / PCPU_MIN_ALLOC_SIZE;
81
82 /*
83 * If a bit is set in the allocation map, the bound_map identifies
84 * where the allocation ends. If the allocation is not set, the
85 * bound_map does not identify free areas as it is only kept accurate
86 * on allocation, not free.
87 *
88 * Positive values are allocations and negative values are free
89 * fragments.
90 */
91 while (start < last_alloc) {
92 if (test_bit(start, chunk->alloc_map)) {
93 end = find_next_bit(chunk->bound_map, last_alloc,
94 start + 1);
95 alloc_sizes[as_len] = 1;
96 } else {
97 end = find_next_bit(chunk->alloc_map, last_alloc,
98 start + 1);
99 alloc_sizes[as_len] = -1;
100 }
101
102 alloc_sizes[as_len++] *= (end - start) * PCPU_MIN_ALLOC_SIZE;
103
104 start = end;
105 }
106
107 /*
108 * The negative values are free fragments and thus sorting gives the
109 * free fragments at the beginning in largest first order.
110 */
111 if (as_len > 0) {
112 sort(alloc_sizes, as_len, sizeof(int), cmpint, NULL);
113
114 /* iterate through the unallocated fragments */
115 for (i = 0, p = alloc_sizes; *p < 0 && i < as_len; i++, p++) {
116 sum_frag -= *p;
117 max_frag = max(max_frag, -1 * (*p));
118 }
119
120 cur_min_alloc = alloc_sizes[i];
121 cur_med_alloc = alloc_sizes[(i + as_len - 1) / 2];
122 cur_max_alloc = alloc_sizes[as_len - 1];
123 }
124
125 P("nr_alloc", chunk->nr_alloc);
126 P("max_alloc_size", chunk->max_alloc_size);
127 P("empty_pop_pages", chunk->nr_empty_pop_pages);
128 P("first_bit", chunk_md->first_free);
129 P("free_bytes", chunk->free_bytes);
130 P("contig_bytes", chunk_md->contig_hint * PCPU_MIN_ALLOC_SIZE);
131 P("sum_frag", sum_frag);
132 P("max_frag", max_frag);
133 P("cur_min_alloc", cur_min_alloc);
134 P("cur_med_alloc", cur_med_alloc);
135 P("cur_max_alloc", cur_max_alloc);
136 #ifdef CONFIG_MEMCG_KMEM
137 P("memcg_aware", pcpu_is_memcg_chunk(pcpu_chunk_type(chunk)));
138 #endif
139 seq_putc(m, '\n');
140 }
141
percpu_stats_show(struct seq_file * m,void * v)142 static int percpu_stats_show(struct seq_file *m, void *v)
143 {
144 struct pcpu_chunk *chunk;
145 int slot, max_nr_alloc;
146 int *buffer;
147 enum pcpu_chunk_type type;
148
149 alloc_buffer:
150 spin_lock_irq(&pcpu_lock);
151 max_nr_alloc = find_max_nr_alloc();
152 spin_unlock_irq(&pcpu_lock);
153
154 /* there can be at most this many free and allocated fragments */
155 buffer = vmalloc(array_size(sizeof(int), (2 * max_nr_alloc + 1)));
156 if (!buffer)
157 return -ENOMEM;
158
159 spin_lock_irq(&pcpu_lock);
160
161 /* if the buffer allocated earlier is too small */
162 if (max_nr_alloc < find_max_nr_alloc()) {
163 spin_unlock_irq(&pcpu_lock);
164 vfree(buffer);
165 goto alloc_buffer;
166 }
167
168 #define PL(X) \
169 seq_printf(m, " %-20s: %12lld\n", #X, (long long int)pcpu_stats_ai.X)
170
171 seq_printf(m,
172 "Percpu Memory Statistics\n"
173 "Allocation Info:\n"
174 "----------------------------------------\n");
175 PL(unit_size);
176 PL(static_size);
177 PL(reserved_size);
178 PL(dyn_size);
179 PL(atom_size);
180 PL(alloc_size);
181 seq_putc(m, '\n');
182
183 #undef PL
184
185 #define PU(X) \
186 seq_printf(m, " %-20s: %12llu\n", #X, (unsigned long long)pcpu_stats.X)
187
188 seq_printf(m,
189 "Global Stats:\n"
190 "----------------------------------------\n");
191 PU(nr_alloc);
192 PU(nr_dealloc);
193 PU(nr_cur_alloc);
194 PU(nr_max_alloc);
195 PU(nr_chunks);
196 PU(nr_max_chunks);
197 PU(min_alloc_size);
198 PU(max_alloc_size);
199 P("empty_pop_pages", pcpu_nr_empty_pop_pages);
200 seq_putc(m, '\n');
201
202 #undef PU
203
204 seq_printf(m,
205 "Per Chunk Stats:\n"
206 "----------------------------------------\n");
207
208 if (pcpu_reserved_chunk) {
209 seq_puts(m, "Chunk: <- Reserved Chunk\n");
210 chunk_map_stats(m, pcpu_reserved_chunk, buffer);
211 }
212
213 for (type = 0; type < PCPU_NR_CHUNK_TYPES; type++) {
214 for (slot = 0; slot < pcpu_nr_slots; slot++) {
215 list_for_each_entry(chunk, &pcpu_chunk_list(type)[slot],
216 list) {
217 if (chunk == pcpu_first_chunk) {
218 seq_puts(m, "Chunk: <- First Chunk\n");
219 chunk_map_stats(m, chunk, buffer);
220 } else {
221 seq_puts(m, "Chunk:\n");
222 chunk_map_stats(m, chunk, buffer);
223 }
224 }
225 }
226 }
227
228 spin_unlock_irq(&pcpu_lock);
229
230 vfree(buffer);
231
232 return 0;
233 }
234 DEFINE_SHOW_ATTRIBUTE(percpu_stats);
235
init_percpu_stats_debugfs(void)236 static int __init init_percpu_stats_debugfs(void)
237 {
238 debugfs_create_file("percpu_stats", 0444, NULL, NULL,
239 &percpu_stats_fops);
240
241 return 0;
242 }
243
244 late_initcall(init_percpu_stats_debugfs);
245
