| /* SPDX-License-Identifier: GPL-2.0-only */ |
| /* |
| * Fast and scalable bitmaps. |
| * |
| * Copyright (C) 2016 Facebook |
| * Copyright (C) 2013-2014 Jens Axboe |
| */ |
| |
| #ifndef __LINUX_SCALE_BITMAP_H |
| #define __LINUX_SCALE_BITMAP_H |
| |
| #include <linux/atomic.h> |
| #include <linux/bitops.h> |
| #include <linux/cache.h> |
| #include <linux/list.h> |
| #include <linux/log2.h> |
| #include <linux/minmax.h> |
| #include <linux/percpu.h> |
| #include <linux/slab.h> |
| #include <linux/smp.h> |
| #include <linux/types.h> |
| #include <linux/wait.h> |
| |
| struct seq_file; |
| |
| /** |
| * struct sbitmap_word - Word in a &struct sbitmap. |
| */ |
| struct sbitmap_word { |
| /** |
| * @depth: Number of bits being used in @word/@cleared |
| */ |
| unsigned long depth; |
| |
| /** |
| * @word: word holding free bits |
| */ |
| unsigned long word ____cacheline_aligned_in_smp; |
| |
| /** |
| * @cleared: word holding cleared bits |
| */ |
| unsigned long cleared ____cacheline_aligned_in_smp; |
| } ____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; |
| |
| /** |
| * @round_robin: Allocate bits in strict round-robin order. |
| */ |
| bool round_robin; |
| |
| /** |
| * @map: Allocated bitmap. |
| */ |
| struct sbitmap_word *map; |
| |
| /* |
| * @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; |
| }; |
| |
| #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; |
| |
| /** |
| * @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; |
| |
| /* |
| * @ws_active: count of currently active ws waitqueues |
| */ |
| atomic_t ws_active; |
| |
| /** |
| * @min_shallow_depth: The minimum shallow depth which may be passed to |
| * sbitmap_queue_get_shallow() or __sbitmap_queue_get_shallow(). |
| */ |
| unsigned int min_shallow_depth; |
| }; |
| |
| /** |
| * 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. |
| * @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). |
| * @alloc_hint: If true, apply percpu hint for where to start searching for |
| * a free bit. |
| * |
| * 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, bool round_robin, bool alloc_hint); |
| |
| /** |
| * sbitmap_free() - Free memory used by a &struct sbitmap. |
| * @sb: Bitmap to free. |
| */ |
| static inline void sbitmap_free(struct sbitmap *sb) |
| { |
| free_percpu(sb->alloc_hint); |
| 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. |
| * |
| * This operation provides acquire barrier semantics if it succeeds. |
| * |
| * Return: Non-negative allocated bit number if successful, -1 otherwise. |
| */ |
| int sbitmap_get(struct sbitmap *sb); |
| |
| /** |
| * 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. |
| * @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 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); |
| |
| #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) { |
| unsigned long word; |
| unsigned int depth = min_t(unsigned int, |
| sb->map[index].depth - nr, |
| sb->depth - scanned); |
| |
| scanned += depth; |
| word = sb->map[index].word & ~sb->map[index].cleared; |
| if (!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, 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)); |
| } |
| |
| /* |
| * This one is special, since it doesn't actually clear the bit, rather it |
| * sets the corresponding bit in the ->cleared mask instead. Paired with |
| * the caller doing sbitmap_deferred_clear() if a given index is full, which |
| * will clear the previously freed entries in the corresponding ->word. |
| */ |
| static inline void sbitmap_deferred_clear_bit(struct sbitmap *sb, unsigned int bitnr) |
| { |
| unsigned long *addr = &sb->map[SB_NR_TO_INDEX(sb, bitnr)].cleared; |
| |
| set_bit(SB_NR_TO_BIT(sb, bitnr), addr); |
| } |
| |
| /* |
| * Pair of sbitmap_get, and this one applies both cleared bit and |
| * allocation hint. |
| */ |
| static inline void sbitmap_put(struct sbitmap *sb, unsigned int bitnr) |
| { |
| sbitmap_deferred_clear_bit(sb, bitnr); |
| |
| if (likely(sb->alloc_hint && !sb->round_robin && bitnr < sb->depth)) |
| *raw_cpu_ptr(sb->alloc_hint) = 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)); |
| } |
| |
| static inline int sbitmap_calculate_shift(unsigned int depth) |
| { |
| int shift = ilog2(BITS_PER_LONG); |
| |
| /* |
| * If the bitmap is small, shrink the number of bits per word so |
| * we spread over a few cachelines, at least. If less than 4 |
| * bits, just forget about it, it's not going to work optimally |
| * anyway. |
| */ |
| if (depth >= 4) { |
| while ((4U << shift) > depth) |
| shift--; |
| } |
| |
| return shift; |
| } |
| |
| /** |
| * 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_weight() - Return how many set and not cleared bits in a &struct |
| * sbitmap. |
| * @sb: Bitmap to check. |
| * |
| * Return: How many set and not cleared bits set |
| */ |
| unsigned int sbitmap_weight(const struct sbitmap *sb); |
| |
| /** |
| * 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); |
| 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_batch() - Try to allocate a batch of free bits |
| * @sbq: Bitmap queue to allocate from. |
| * @nr_tags: number of tags requested |
| * @offset: offset to add to returned bits |
| * |
| * Return: Mask of allocated tags, 0 if none are found. Each tag allocated is |
| * a bit in the mask returned, and the caller must add @offset to the value to |
| * get the absolute tag value. |
| */ |
| unsigned long __sbitmap_queue_get_batch(struct sbitmap_queue *sbq, int nr_tags, |
| unsigned int *offset); |
| |
| /** |
| * __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(). |
| * |
| * If you call this, make sure to call sbitmap_queue_min_shallow_depth() after |
| * initializing @sbq. |
| * |
| * 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(). |
| * |
| * If you call this, make sure to call sbitmap_queue_min_shallow_depth() after |
| * initializing @sbq. |
| * |
| * 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_min_shallow_depth() - Inform a &struct sbitmap_queue of the |
| * minimum shallow depth that will be used. |
| * @sbq: Bitmap queue in question. |
| * @min_shallow_depth: The minimum shallow depth that will be passed to |
| * sbitmap_queue_get_shallow() or __sbitmap_queue_get_shallow(). |
| * |
| * sbitmap_queue_clear() batches wakeups as an optimization. The batch size |
| * depends on the depth of the bitmap. Since the shallow allocation functions |
| * effectively operate with a different depth, the shallow depth must be taken |
| * into account when calculating the batch size. This function must be called |
| * with the minimum shallow depth that will be used. Failure to do so can result |
| * in missed wakeups. |
| */ |
| void sbitmap_queue_min_shallow_depth(struct sbitmap_queue *sbq, |
| unsigned int min_shallow_depth); |
| |
| /** |
| * 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); |
| |
| /** |
| * sbitmap_queue_clear_batch() - Free a batch of allocated bits |
| * &struct sbitmap_queue. |
| * @sbq: Bitmap to free from. |
| * @offset: offset for each tag in array |
| * @tags: array of tags |
| * @nr_tags: number of tags in array |
| */ |
| void sbitmap_queue_clear_batch(struct sbitmap_queue *sbq, int offset, |
| int *tags, int nr_tags); |
| |
| 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_wake_up() - Wake up some of waiters in one waitqueue |
| * on a &struct sbitmap_queue. |
| * @sbq: Bitmap queue to wake up. |
| */ |
| void sbitmap_queue_wake_up(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); |
| |
| struct sbq_wait { |
| struct sbitmap_queue *sbq; /* if set, sbq_wait is accounted */ |
| struct wait_queue_entry wait; |
| }; |
| |
| #define DEFINE_SBQ_WAIT(name) \ |
| struct sbq_wait name = { \ |
| .sbq = NULL, \ |
| .wait = { \ |
| .private = current, \ |
| .func = autoremove_wake_function, \ |
| .entry = LIST_HEAD_INIT((name).wait.entry), \ |
| } \ |
| } |
| |
| /* |
| * Wrapper around prepare_to_wait_exclusive(), which maintains some extra |
| * internal state. |
| */ |
| void sbitmap_prepare_to_wait(struct sbitmap_queue *sbq, |
| struct sbq_wait_state *ws, |
| struct sbq_wait *sbq_wait, int state); |
| |
| /* |
| * Must be paired with sbitmap_prepare_to_wait(). |
| */ |
| void sbitmap_finish_wait(struct sbitmap_queue *sbq, struct sbq_wait_state *ws, |
| struct sbq_wait *sbq_wait); |
| |
| /* |
| * Wrapper around add_wait_queue(), which maintains some extra internal state |
| */ |
| void sbitmap_add_wait_queue(struct sbitmap_queue *sbq, |
| struct sbq_wait_state *ws, |
| struct sbq_wait *sbq_wait); |
| |
| /* |
| * Must be paired with sbitmap_add_wait_queue() |
| */ |
| void sbitmap_del_wait_queue(struct sbq_wait *sbq_wait); |
| |
| #endif /* __LINUX_SCALE_BITMAP_H */ |