348 lines
7.9 KiB
C
348 lines
7.9 KiB
C
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/*
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* Copyright (C) 2016 Facebook
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* Copyright (C) 2013-2014 Jens Axboe
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License v2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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#include <linux/random.h>
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#include <linux/sbitmap.h>
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int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
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gfp_t flags, int node)
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{
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unsigned int bits_per_word;
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unsigned int i;
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if (shift < 0) {
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shift = ilog2(BITS_PER_LONG);
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/*
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* If the bitmap is small, shrink the number of bits per word so
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* we spread over a few cachelines, at least. If less than 4
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* bits, just forget about it, it's not going to work optimally
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* anyway.
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*/
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if (depth >= 4) {
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while ((4U << shift) > depth)
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shift--;
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}
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}
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bits_per_word = 1U << shift;
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if (bits_per_word > BITS_PER_LONG)
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return -EINVAL;
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sb->shift = shift;
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sb->depth = depth;
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sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);
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if (depth == 0) {
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sb->map = NULL;
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return 0;
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}
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sb->map = kzalloc_node(sb->map_nr * sizeof(*sb->map), flags, node);
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if (!sb->map)
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return -ENOMEM;
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for (i = 0; i < sb->map_nr; i++) {
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sb->map[i].depth = min(depth, bits_per_word);
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depth -= sb->map[i].depth;
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}
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return 0;
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}
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EXPORT_SYMBOL_GPL(sbitmap_init_node);
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void sbitmap_resize(struct sbitmap *sb, unsigned int depth)
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{
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unsigned int bits_per_word = 1U << sb->shift;
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unsigned int i;
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sb->depth = depth;
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sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);
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for (i = 0; i < sb->map_nr; i++) {
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sb->map[i].depth = min(depth, bits_per_word);
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depth -= sb->map[i].depth;
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}
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}
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EXPORT_SYMBOL_GPL(sbitmap_resize);
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static int __sbitmap_get_word(struct sbitmap_word *word, unsigned int hint,
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bool wrap)
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{
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unsigned int orig_hint = hint;
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int nr;
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while (1) {
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nr = find_next_zero_bit(&word->word, word->depth, hint);
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if (unlikely(nr >= word->depth)) {
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/*
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* We started with an offset, and we didn't reset the
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* offset to 0 in a failure case, so start from 0 to
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* exhaust the map.
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*/
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if (orig_hint && hint && wrap) {
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hint = orig_hint = 0;
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continue;
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}
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return -1;
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}
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if (!test_and_set_bit(nr, &word->word))
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break;
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hint = nr + 1;
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if (hint >= word->depth - 1)
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hint = 0;
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}
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return nr;
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}
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int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin)
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{
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unsigned int i, index;
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int nr = -1;
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index = SB_NR_TO_INDEX(sb, alloc_hint);
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for (i = 0; i < sb->map_nr; i++) {
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nr = __sbitmap_get_word(&sb->map[index],
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SB_NR_TO_BIT(sb, alloc_hint),
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!round_robin);
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if (nr != -1) {
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nr += index << sb->shift;
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break;
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}
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/* Jump to next index. */
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index++;
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alloc_hint = index << sb->shift;
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if (index >= sb->map_nr) {
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index = 0;
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alloc_hint = 0;
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}
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}
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return nr;
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}
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EXPORT_SYMBOL_GPL(sbitmap_get);
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bool sbitmap_any_bit_set(const struct sbitmap *sb)
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{
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unsigned int i;
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for (i = 0; i < sb->map_nr; i++) {
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if (sb->map[i].word)
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return true;
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}
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return false;
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}
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EXPORT_SYMBOL_GPL(sbitmap_any_bit_set);
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bool sbitmap_any_bit_clear(const struct sbitmap *sb)
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{
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unsigned int i;
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for (i = 0; i < sb->map_nr; i++) {
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const struct sbitmap_word *word = &sb->map[i];
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unsigned long ret;
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ret = find_first_zero_bit(&word->word, word->depth);
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if (ret < word->depth)
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return true;
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}
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return false;
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}
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EXPORT_SYMBOL_GPL(sbitmap_any_bit_clear);
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unsigned int sbitmap_weight(const struct sbitmap *sb)
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{
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unsigned int i, weight = 0;
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for (i = 0; i < sb->map_nr; i++) {
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const struct sbitmap_word *word = &sb->map[i];
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weight += bitmap_weight(&word->word, word->depth);
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}
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return weight;
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}
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EXPORT_SYMBOL_GPL(sbitmap_weight);
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static unsigned int sbq_calc_wake_batch(unsigned int depth)
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{
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unsigned int wake_batch;
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/*
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* For each batch, we wake up one queue. We need to make sure that our
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* batch size is small enough that the full depth of the bitmap is
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* enough to wake up all of the queues.
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*/
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wake_batch = SBQ_WAKE_BATCH;
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if (wake_batch > depth / SBQ_WAIT_QUEUES)
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wake_batch = max(1U, depth / SBQ_WAIT_QUEUES);
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return wake_batch;
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}
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int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
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int shift, bool round_robin, gfp_t flags, int node)
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{
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int ret;
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int i;
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ret = sbitmap_init_node(&sbq->sb, depth, shift, flags, node);
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if (ret)
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return ret;
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sbq->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
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if (!sbq->alloc_hint) {
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sbitmap_free(&sbq->sb);
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return -ENOMEM;
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}
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if (depth && !round_robin) {
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for_each_possible_cpu(i)
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*per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth;
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}
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sbq->wake_batch = sbq_calc_wake_batch(depth);
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atomic_set(&sbq->wake_index, 0);
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sbq->ws = kzalloc_node(SBQ_WAIT_QUEUES * sizeof(*sbq->ws), flags, node);
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if (!sbq->ws) {
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free_percpu(sbq->alloc_hint);
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sbitmap_free(&sbq->sb);
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return -ENOMEM;
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}
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for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
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init_waitqueue_head(&sbq->ws[i].wait);
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atomic_set(&sbq->ws[i].wait_cnt, sbq->wake_batch);
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}
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sbq->round_robin = round_robin;
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return 0;
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}
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EXPORT_SYMBOL_GPL(sbitmap_queue_init_node);
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void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth)
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{
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sbq->wake_batch = sbq_calc_wake_batch(depth);
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sbitmap_resize(&sbq->sb, depth);
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}
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EXPORT_SYMBOL_GPL(sbitmap_queue_resize);
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int __sbitmap_queue_get(struct sbitmap_queue *sbq)
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{
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unsigned int hint, depth;
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int nr;
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hint = this_cpu_read(*sbq->alloc_hint);
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depth = READ_ONCE(sbq->sb.depth);
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if (unlikely(hint >= depth)) {
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hint = depth ? prandom_u32() % depth : 0;
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this_cpu_write(*sbq->alloc_hint, hint);
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}
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nr = sbitmap_get(&sbq->sb, hint, sbq->round_robin);
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if (nr == -1) {
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/* If the map is full, a hint won't do us much good. */
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this_cpu_write(*sbq->alloc_hint, 0);
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} else if (nr == hint || unlikely(sbq->round_robin)) {
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/* Only update the hint if we used it. */
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hint = nr + 1;
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if (hint >= depth - 1)
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hint = 0;
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this_cpu_write(*sbq->alloc_hint, hint);
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}
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return nr;
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}
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EXPORT_SYMBOL_GPL(__sbitmap_queue_get);
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static struct sbq_wait_state *sbq_wake_ptr(struct sbitmap_queue *sbq)
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{
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int i, wake_index;
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wake_index = atomic_read(&sbq->wake_index);
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for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
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struct sbq_wait_state *ws = &sbq->ws[wake_index];
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if (waitqueue_active(&ws->wait)) {
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int o = atomic_read(&sbq->wake_index);
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if (wake_index != o)
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atomic_cmpxchg(&sbq->wake_index, o, wake_index);
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return ws;
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}
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wake_index = sbq_index_inc(wake_index);
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}
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return NULL;
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}
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static void sbq_wake_up(struct sbitmap_queue *sbq)
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{
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struct sbq_wait_state *ws;
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int wait_cnt;
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/* Ensure that the wait list checks occur after clear_bit(). */
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smp_mb();
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ws = sbq_wake_ptr(sbq);
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if (!ws)
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return;
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wait_cnt = atomic_dec_return(&ws->wait_cnt);
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if (unlikely(wait_cnt < 0))
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wait_cnt = atomic_inc_return(&ws->wait_cnt);
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if (wait_cnt == 0) {
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atomic_add(sbq->wake_batch, &ws->wait_cnt);
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sbq_index_atomic_inc(&sbq->wake_index);
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wake_up(&ws->wait);
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}
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}
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void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
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unsigned int cpu)
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{
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sbitmap_clear_bit(&sbq->sb, nr);
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sbq_wake_up(sbq);
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if (likely(!sbq->round_robin && nr < sbq->sb.depth))
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*per_cpu_ptr(sbq->alloc_hint, cpu) = nr;
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}
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EXPORT_SYMBOL_GPL(sbitmap_queue_clear);
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void sbitmap_queue_wake_all(struct sbitmap_queue *sbq)
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{
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int i, wake_index;
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/*
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* Make sure all changes prior to this are visible from other CPUs.
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*/
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smp_mb();
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wake_index = atomic_read(&sbq->wake_index);
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for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
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struct sbq_wait_state *ws = &sbq->ws[wake_index];
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if (waitqueue_active(&ws->wait))
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wake_up(&ws->wait);
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wake_index = sbq_index_inc(wake_index);
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}
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}
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EXPORT_SYMBOL_GPL(sbitmap_queue_wake_all);
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