/* * Fast and scalable bitmaps. * * Copyright (C) 2016 Facebook * Copyright (C) 2013-2014 Jens Axboe * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public * License v2 as published by the Free Software Foundation. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see <https://www.gnu.org/licenses/>. */ #ifndef __LINUX_SCALE_BITMAP_H #define __LINUX_SCALE_BITMAP_H #include <linux/kernel.h> #include <linux/slab.h> /** * struct sbitmap_word - Word in a &struct sbitmap. */ struct sbitmap_word { /** * @word: The bitmap word itself. */ unsigned long word; /** * @depth: Number of bits being used in @word. */ unsigned long depth; } ____cacheline_aligned_in_smp; /** * struct sbitmap - Scalable bitmap. * * A &struct sbitmap is spread over multiple cachelines to avoid ping-pong. This * trades off higher memory usage for better scalability. */ struct sbitmap { /** * @depth: Number of bits used in the whole bitmap. */ unsigned int depth; /** * @shift: log2(number of bits used per word) */ unsigned int shift; /** * @map_nr: Number of words (cachelines) being used for the bitmap. */ unsigned int map_nr; /** * @map: Allocated bitmap. */ struct sbitmap_word *map; }; #define SBQ_WAIT_QUEUES 8 #define SBQ_WAKE_BATCH 8 /** * struct sbq_wait_state - Wait queue in a &struct sbitmap_queue. */ struct sbq_wait_state { /** * @wait_cnt: Number of frees remaining before we wake up. */ atomic_t wait_cnt; /** * @wait: Wait queue. */ wait_queue_head_t wait; } ____cacheline_aligned_in_smp; /** * struct sbitmap_queue - Scalable bitmap with the added ability to wait on free * bits. * * A &struct sbitmap_queue uses multiple wait queues and rolling wakeups to * avoid contention on the wait queue spinlock. This ensures that we don't hit a * scalability wall when we run out of free bits and have to start putting tasks * to sleep. */ struct sbitmap_queue { /** * @sb: Scalable bitmap. */ struct sbitmap sb; /* * @alloc_hint: Cache of last successfully allocated or freed bit. * * This is per-cpu, which allows multiple users to stick to different * cachelines until the map is exhausted. */ unsigned int __percpu *alloc_hint; /** * @wake_batch: Number of bits which must be freed before we wake up any * waiters. */ unsigned int wake_batch; /** * @wake_index: Next wait queue in @ws to wake up. */ atomic_t wake_index; /** * @ws: Wait queues. */ struct sbq_wait_state *ws; /** * @round_robin: Allocate bits in strict round-robin order. */ bool round_robin; }; /** * sbitmap_init_node() - Initialize a &struct sbitmap on a specific memory node. * @sb: Bitmap to initialize. * @depth: Number of bits to allocate. * @shift: Use 2^@shift bits per word in the bitmap; if a negative number if * given, a good default is chosen. * @flags: Allocation flags. * @node: Memory node to allocate on. * * Return: Zero on success or negative errno on failure. */ int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift, gfp_t flags, int node); /** * sbitmap_free() - Free memory used by a &struct sbitmap. * @sb: Bitmap to free. */ static inline void sbitmap_free(struct sbitmap *sb) { kfree(sb->map); sb->map = NULL; } /** * sbitmap_resize() - Resize a &struct sbitmap. * @sb: Bitmap to resize. * @depth: New number of bits to resize to. * * Doesn't reallocate anything. It's up to the caller to ensure that the new * depth doesn't exceed the depth that the sb was initialized with. */ void sbitmap_resize(struct sbitmap *sb, unsigned int depth); /** * sbitmap_get() - Try to allocate a free bit from a &struct sbitmap. * @sb: Bitmap to allocate from. * @alloc_hint: Hint for where to start searching for a free bit. * @round_robin: If true, be stricter about allocation order; always allocate * starting from the last allocated bit. This is less efficient * than the default behavior (false). * * Return: Non-negative allocated bit number if successful, -1 otherwise. */ int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin); /** * sbitmap_get_shallow() - Try to allocate a free bit from a &struct sbitmap, * limiting the depth used from each word. * @sb: Bitmap to allocate from. * @alloc_hint: Hint for where to start searching for a free bit. * @shallow_depth: The maximum number of bits to allocate from a single word. * * This rather specific operation allows for having multiple users with * different allocation limits. E.g., there can be a high-priority class that * uses sbitmap_get() and a low-priority class that uses sbitmap_get_shallow() * with a @shallow_depth of (1 << (@sb->shift - 1)). Then, the low-priority * class can only allocate half of the total bits in the bitmap, preventing it * from starving out the high-priority class. * * Return: Non-negative allocated bit number if successful, -1 otherwise. */ int sbitmap_get_shallow(struct sbitmap *sb, unsigned int alloc_hint, unsigned long shallow_depth); /** * sbitmap_any_bit_set() - Check for a set bit in a &struct sbitmap. * @sb: Bitmap to check. * * Return: true if any bit in the bitmap is set, false otherwise. */ bool sbitmap_any_bit_set(const struct sbitmap *sb); /** * sbitmap_any_bit_clear() - Check for an unset bit in a &struct * sbitmap. * @sb: Bitmap to check. * * Return: true if any bit in the bitmap is clear, false otherwise. */ bool sbitmap_any_bit_clear(const struct sbitmap *sb); #define SB_NR_TO_INDEX(sb, bitnr) ((bitnr) >> (sb)->shift) #define SB_NR_TO_BIT(sb, bitnr) ((bitnr) & ((1U << (sb)->shift) - 1U)) typedef bool (*sb_for_each_fn)(struct sbitmap *, unsigned int, void *); /** * __sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap. * @start: Where to start the iteration. * @sb: Bitmap to iterate over. * @fn: Callback. Should return true to continue or false to break early. * @data: Pointer to pass to callback. * * This is inline even though it's non-trivial so that the function calls to the * callback will hopefully get optimized away. */ static inline void __sbitmap_for_each_set(struct sbitmap *sb, unsigned int start, sb_for_each_fn fn, void *data) { unsigned int index; unsigned int nr; unsigned int scanned = 0; if (start >= sb->depth) start = 0; index = SB_NR_TO_INDEX(sb, start); nr = SB_NR_TO_BIT(sb, start); while (scanned < sb->depth) { struct sbitmap_word *word = &sb->map[index]; unsigned int depth = min_t(unsigned int, word->depth - nr, sb->depth - scanned); scanned += depth; if (!word->word) goto next; /* * On the first iteration of the outer loop, we need to add the * bit offset back to the size of the word for find_next_bit(). * On all other iterations, nr is zero, so this is a noop. */ depth += nr; while (1) { nr = find_next_bit(&word->word, depth, nr); if (nr >= depth) break; if (!fn(sb, (index << sb->shift) + nr, data)) return; nr++; } next: nr = 0; if (++index >= sb->map_nr) index = 0; } } /** * sbitmap_for_each_set() - Iterate over each set bit in a &struct sbitmap. * @sb: Bitmap to iterate over. * @fn: Callback. Should return true to continue or false to break early. * @data: Pointer to pass to callback. */ static inline void sbitmap_for_each_set(struct sbitmap *sb, sb_for_each_fn fn, void *data) { __sbitmap_for_each_set(sb, 0, fn, data); } static inline unsigned long *__sbitmap_word(struct sbitmap *sb, unsigned int bitnr) { return &sb->map[SB_NR_TO_INDEX(sb, bitnr)].word; } /* Helpers equivalent to the operations in asm/bitops.h and linux/bitmap.h */ static inline void sbitmap_set_bit(struct sbitmap *sb, unsigned int bitnr) { set_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr)); } static inline void sbitmap_clear_bit(struct sbitmap *sb, unsigned int bitnr) { clear_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr)); } static inline int sbitmap_test_bit(struct sbitmap *sb, unsigned int bitnr) { return test_bit(SB_NR_TO_BIT(sb, bitnr), __sbitmap_word(sb, bitnr)); } unsigned int sbitmap_weight(const struct sbitmap *sb); /** * sbitmap_show() - Dump &struct sbitmap information to a &struct seq_file. * @sb: Bitmap to show. * @m: struct seq_file to write to. * * This is intended for debugging. The format may change at any time. */ void sbitmap_show(struct sbitmap *sb, struct seq_file *m); /** * sbitmap_bitmap_show() - Write a hex dump of a &struct sbitmap to a &struct * seq_file. * @sb: Bitmap to show. * @m: struct seq_file to write to. * * This is intended for debugging. The output isn't guaranteed to be internally * consistent. */ void sbitmap_bitmap_show(struct sbitmap *sb, struct seq_file *m); /** * sbitmap_queue_init_node() - Initialize a &struct sbitmap_queue on a specific * memory node. * @sbq: Bitmap queue to initialize. * @depth: See sbitmap_init_node(). * @shift: See sbitmap_init_node(). * @round_robin: See sbitmap_get(). * @flags: Allocation flags. * @node: Memory node to allocate on. * * Return: Zero on success or negative errno on failure. */ int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth, int shift, bool round_robin, gfp_t flags, int node); /** * sbitmap_queue_free() - Free memory used by a &struct sbitmap_queue. * * @sbq: Bitmap queue to free. */ static inline void sbitmap_queue_free(struct sbitmap_queue *sbq) { kfree(sbq->ws); free_percpu(sbq->alloc_hint); sbitmap_free(&sbq->sb); } /** * sbitmap_queue_resize() - Resize a &struct sbitmap_queue. * @sbq: Bitmap queue to resize. * @depth: New number of bits to resize to. * * Like sbitmap_resize(), this doesn't reallocate anything. It has to do * some extra work on the &struct sbitmap_queue, so it's not safe to just * resize the underlying &struct sbitmap. */ void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth); /** * __sbitmap_queue_get() - Try to allocate a free bit from a &struct * sbitmap_queue with preemption already disabled. * @sbq: Bitmap queue to allocate from. * * Return: Non-negative allocated bit number if successful, -1 otherwise. */ int __sbitmap_queue_get(struct sbitmap_queue *sbq); /** * __sbitmap_queue_get_shallow() - Try to allocate a free bit from a &struct * sbitmap_queue, limiting the depth used from each word, with preemption * already disabled. * @sbq: Bitmap queue to allocate from. * @shallow_depth: The maximum number of bits to allocate from a single word. * See sbitmap_get_shallow(). * * Return: Non-negative allocated bit number if successful, -1 otherwise. */ int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq, unsigned int shallow_depth); /** * sbitmap_queue_get() - Try to allocate a free bit from a &struct * sbitmap_queue. * @sbq: Bitmap queue to allocate from. * @cpu: Output parameter; will contain the CPU we ran on (e.g., to be passed to * sbitmap_queue_clear()). * * Return: Non-negative allocated bit number if successful, -1 otherwise. */ static inline int sbitmap_queue_get(struct sbitmap_queue *sbq, unsigned int *cpu) { int nr; *cpu = get_cpu(); nr = __sbitmap_queue_get(sbq); put_cpu(); return nr; } /** * sbitmap_queue_get_shallow() - Try to allocate a free bit from a &struct * sbitmap_queue, limiting the depth used from each word. * @sbq: Bitmap queue to allocate from. * @cpu: Output parameter; will contain the CPU we ran on (e.g., to be passed to * sbitmap_queue_clear()). * @shallow_depth: The maximum number of bits to allocate from a single word. * See sbitmap_get_shallow(). * * Return: Non-negative allocated bit number if successful, -1 otherwise. */ static inline int sbitmap_queue_get_shallow(struct sbitmap_queue *sbq, unsigned int *cpu, unsigned int shallow_depth) { int nr; *cpu = get_cpu(); nr = __sbitmap_queue_get_shallow(sbq, shallow_depth); put_cpu(); return nr; } /** * sbitmap_queue_clear() - Free an allocated bit and wake up waiters on a * &struct sbitmap_queue. * @sbq: Bitmap to free from. * @nr: Bit number to free. * @cpu: CPU the bit was allocated on. */ void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr, unsigned int cpu); static inline int sbq_index_inc(int index) { return (index + 1) & (SBQ_WAIT_QUEUES - 1); } static inline void sbq_index_atomic_inc(atomic_t *index) { int old = atomic_read(index); int new = sbq_index_inc(old); atomic_cmpxchg(index, old, new); } /** * sbq_wait_ptr() - Get the next wait queue to use for a &struct * sbitmap_queue. * @sbq: Bitmap queue to wait on. * @wait_index: A counter per "user" of @sbq. */ static inline struct sbq_wait_state *sbq_wait_ptr(struct sbitmap_queue *sbq, atomic_t *wait_index) { struct sbq_wait_state *ws; ws = &sbq->ws[atomic_read(wait_index)]; sbq_index_atomic_inc(wait_index); return ws; } /** * sbitmap_queue_wake_all() - Wake up everything waiting on a &struct * sbitmap_queue. * @sbq: Bitmap queue to wake up. */ void sbitmap_queue_wake_all(struct sbitmap_queue *sbq); /** * sbitmap_queue_show() - Dump &struct sbitmap_queue information to a &struct * seq_file. * @sbq: Bitmap queue to show. * @m: struct seq_file to write to. * * This is intended for debugging. The format may change at any time. */ void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m); #endif /* __LINUX_SCALE_BITMAP_H */