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
 22struct percpu_stats pcpu_stats;
 23struct pcpu_alloc_info pcpu_stats_ai;
 24
 25static 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 */
 33static 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 */
 52static 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
135static 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
141alloc_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(2 * max_nr_alloc + 1, sizeof(int));
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}
225DEFINE_SHOW_ATTRIBUTE(percpu_stats);
226
227static 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
235late_initcall(init_percpu_stats_debugfs);