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