1 /* SPDX-License-Identifier: MIT */
2 /* SPDX-FileCopyrightText: 2024 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> */
4 #ifndef _RSEQ_PERCPU_ALLOC_H
5 #define _RSEQ_PERCPU_ALLOC_H
12 * rseq/percpu-alloc.h: rseq CPU-Local Storage (CLS) memory allocator.
14 * The rseq per-CPU memory allocator allows the application the request
15 * memory pools of CPU-Local memory each of containing objects of a
16 * given size (rounded to next power of 2), reserving a given virtual
17 * address size per CPU, for a given maximum number of CPUs.
19 * The per-CPU memory allocator is analogous to TLS (Thread-Local
20 * Storage) memory: TLS is Thread-Local Storage, whereas the per-CPU
21 * memory allocator provides CPU-Local Storage.
29 * Tag pointers returned by:
30 * - rseq_percpu_malloc(),
31 * - rseq_percpu_zmalloc(),
32 * - rseq_percpu_pool_set_malloc(),
33 * - rseq_percpu_pool_set_zmalloc().
35 * and passed as parameter to:
36 * - rseq_percpu_ptr(),
37 * - rseq_percpu_free().
39 * with __rseq_percpu for use by static analyzers.
43 struct rseq_mmap_attr
;
44 struct rseq_percpu_pool
;
47 * rseq_percpu_pool_create: Create a per-cpu memory pool.
49 * Create a per-cpu memory pool for items of size @item_len (rounded to
50 * next power of two). The reserved allocation size is @percpu_len, and
51 * the maximum CPU value expected is (@max_nr_cpus - 1).
53 * The @mmap_attr pointer used to specify the memory allocator callbacks
54 * to use to manage the memory for the pool. If NULL, use a default
55 * internal implementation. The @mmap_attr can be destroyed immediately
56 * after rseq_percpu_pool_create() returns. The caller keeps ownership
59 * Argument @flags is currently expected to be 0. This is for future
62 * Returns a pointer to the created percpu pool. Return NULL on error,
63 * with errno set accordingly:
64 * EINVAL: Invalid argument.
65 * ENOMEM: Not enough resources (memory or pool indexes) available to
68 * In addition, if the mmap_attr mmap callback fails, NULL is returned
69 * and errno is propagated from the callback. The default callback can
70 * return errno=ENOMEM.
72 * This API is MT-safe.
74 struct rseq_percpu_pool
*rseq_percpu_pool_create(size_t item_len
,
75 size_t percpu_len
, int max_nr_cpus
,
76 const struct rseq_mmap_attr
*mmap_attr
,
80 * rseq_percpu_pool_destroy: Destroy a per-cpu memory pool.
82 * Destroy a per-cpu memory pool, unmapping its memory and removing the
83 * pool entry from the global index. No pointers allocated from the
84 * pool should be used when it is destroyed. This includes rseq_percpu_ptr().
86 * Argument @pool is a pointer to the per-cpu pool to destroy.
88 * Return values: 0 on success, -1 on error, with errno set accordingly:
89 * ENOENT: Trying to free a pool which was not allocated.
91 * If the munmap_func callback fails, -1 is returned and errno is
92 * propagated from the callback. The default callback can return
95 * This API is MT-safe.
97 int rseq_percpu_pool_destroy(struct rseq_percpu_pool
*pool
);
100 * rseq_percpu_malloc: Allocate memory from a per-cpu pool.
102 * Allocate an item from a per-cpu @pool. The allocation will reserve
103 * an item of the size specified by @item_len (rounded to next power of
104 * two) at pool creation. This effectively reserves space for this item
107 * On success, return a "__rseq_percpu" encoded pointer to the pool
108 * item. This encoded pointer is meant to be passed to rseq_percpu_ptr()
109 * to be decoded to a valid address before being accessed.
111 * Return NULL (errno=ENOMEM) if there is not enough space left in the
112 * pool to allocate an item.
114 * This API is MT-safe.
116 void __rseq_percpu
*rseq_percpu_malloc(struct rseq_percpu_pool
*pool
);
119 * rseq_percpu_zmalloc: Allocated zero-initialized memory from a per-cpu pool.
121 * Allocate memory for an item within the pool, and zero-initialize its
122 * memory on all CPUs. See rseq_percpu_malloc for details.
124 * This API is MT-safe.
126 void __rseq_percpu
*rseq_percpu_zmalloc(struct rseq_percpu_pool
*pool
);
129 * rseq_percpu_free: Free memory from a per-cpu pool.
131 * Free an item pointed to by @ptr from its per-cpu pool.
133 * The @ptr argument is a __rseq_percpu encoded pointer returned by
136 * - rseq_percpu_malloc(),
137 * - rseq_percpu_zmalloc(),
138 * - rseq_percpu_pool_set_malloc(),
139 * - rseq_percpu_pool_set_zmalloc().
141 * This API is MT-safe.
143 void rseq_percpu_free(void __rseq_percpu
*ptr
);
146 * rseq_percpu_ptr: Decode a per-cpu pointer.
148 * Decode a per-cpu pointer @ptr to get the associated pointer for the
149 * given @cpu. The @ptr argument is a __rseq_percpu encoded pointer
150 * returned by either:
152 * - rseq_percpu_malloc(),
153 * - rseq_percpu_zmalloc(),
154 * - rseq_percpu_pool_set_malloc(),
155 * - rseq_percpu_pool_set_zmalloc().
157 * The __rseq_percpu pointer can be decoded with rseq_percpu_ptr() even
158 * after it has been freed, as long as its associated pool has not been
159 * destroyed. However, memory pointed to by the decoded pointer should
160 * not be accessed after the __rseq_percpu pointer has been freed.
162 * The macro rseq_percpu_ptr() preserves the type of the @ptr parameter
163 * for the returned pointer, but removes the __rseq_percpu annotation.
165 * This API is MT-safe.
167 void *__rseq_percpu_ptr(void __rseq_percpu
*ptr
, int cpu
);
168 #define rseq_percpu_ptr(ptr, cpu) ((__typeof__(*(ptr)) *) __rseq_percpu_ptr(ptr, cpu))
171 * rseq_percpu_pool_cpu_offset: Return the offset from encoded to decoded percpu pointer.
173 * Calculate the offset from any __rseq_percpu pointer allocated from
174 * the pool to its associated per-cpu data for @cpu.
176 * This API is MT-safe.
178 ptrdiff_t rseq_percpu_pool_ptr_offset(struct rseq_percpu_pool
*pool
, int cpu
);
181 * rseq_percpu_pool_set_create: Create a pool set.
183 * Create a set of pools. Its purpose is to offer a memory allocator API
184 * for variable-length items (e.g. variable length strings). When
185 * created, the pool set has no pool. Pools can be created and added to
186 * the set. One common approach would be to create pools for each
187 * relevant power of two allocation size useful for the application.
188 * Only one pool can be added to the pool set for each power of two
191 * Returns a pool set pointer on success, else returns NULL with
192 * errno=ENOMEM (out of memory).
194 * This API is MT-safe.
196 struct rseq_percpu_pool_set
*rseq_percpu_pool_set_create(void);
199 * rseq_percpu_pool_set_destroy: Destroy a pool set.
201 * Destroy a pool set and its associated resources. The pools that were
202 * added to the pool set are destroyed as well.
204 * Returns 0 on success, -1 on failure (or partial failure), with errno
205 * set by rseq_percpu_pool_destroy(). Using a pool set after destroy
206 * failure is undefined.
208 * This API is MT-safe.
210 int rseq_percpu_pool_set_destroy(struct rseq_percpu_pool_set
*pool_set
);
213 * rseq_percpu_pool_set_add_pool: Add a pool to a pool set.
215 * Add a @pool to the @pool_set. On success, its ownership is handed
216 * over to the pool set, so the caller should not destroy it explicitly.
217 * Only one pool can be added to the pool set for each power of two
220 * Returns 0 on success, -1 on error with the following errno:
221 * - EBUSY: A pool already exists in the pool set for this power of two
224 * This API is MT-safe.
226 int rseq_percpu_pool_set_add_pool(struct rseq_percpu_pool_set
*pool_set
,
227 struct rseq_percpu_pool
*pool
);
230 * rseq_percpu_pool_set_malloc: Allocate memory from a per-cpu pool set.
232 * Allocate an item from a per-cpu @pool. The allocation will reserve
233 * an item of the size specified by @len (rounded to next power of
234 * two). This effectively reserves space for this item on all CPUs.
236 * The space reservation will search for the smallest pool within
237 * @pool_set which respects the following conditions:
239 * - it has an item size large enough to fit @len,
240 * - it has space available.
242 * On success, return a "__rseq_percpu" encoded pointer to the pool
243 * item. This encoded pointer is meant to be passed to rseq_percpu_ptr()
244 * to be decoded to a valid address before being accessed.
246 * Return NULL (errno=ENOMEM) if there is not enough space left in the
247 * pool to allocate an item.
249 * This API is MT-safe.
251 void __rseq_percpu
*rseq_percpu_pool_set_malloc(struct rseq_percpu_pool_set
*pool_set
, size_t len
);
254 * rseq_percpu_pool_set_zmalloc: Allocated zero-initialized memory from a per-cpu pool set.
256 * Allocate memory for an item within the pool, and zero-initialize its
257 * memory on all CPUs. See rseq_percpu_pool_set_malloc for details.
259 * This API is MT-safe.
261 void __rseq_percpu
*rseq_percpu_pool_set_zmalloc(struct rseq_percpu_pool_set
*pool_set
, size_t len
);
264 * rseq_percpu_pool_init_numa: Move pages to the NUMA node associated to their CPU topology.
266 * For pages allocated within @pool, invoke move_pages(2) with the given
267 * @numa_flags to move the pages to the NUMA node associated to their
270 * Argument @numa_flags are passed to move_pages(2). The expected flags are:
271 * MPOL_MF_MOVE: move process-private pages to cpu-specific numa nodes.
272 * MPOL_MF_MOVE_ALL: move shared pages to cpu-specific numa nodes
273 * (requires CAP_SYS_NICE).
275 * Returns 0 on success, else return -1 with errno set by move_pages(2).
277 int rseq_percpu_pool_init_numa(struct rseq_percpu_pool
*pool
, int numa_flags
);
280 * rseq_mmap_attr_create: Create a mmap attribute structure.
282 * The @mmap_func callback used to map the memory for the pool.
284 * The @munmap_func callback used to unmap the memory when the pool
287 * The @mmap_priv argument is a private data pointer passed to both
288 * @mmap_func and @munmap_func callbacks.
290 struct rseq_mmap_attr
*rseq_mmap_attr_create(void *(*mmap_func
)(void *priv
, size_t len
),
291 int (*munmap_func
)(void *priv
, void *ptr
, size_t len
),
295 * rseq_mmap_attr_destroy: Destroy a mmap attribute structure.
297 void rseq_mmap_attr_destroy(struct rseq_mmap_attr
*attr
);
303 #endif /* _RSEQ_PERCPU_ALLOC_H */
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