FreeBSD/Linux Kernel Cross Reference
sys/vm/uma_int.h
1 /*-
2 * Copyright (c) 2002, 2003, 2004, 2005 Jeffrey Roberson <jeff@FreeBSD.org>
3 * Copyright (c) 2004, 2005 Bosko Milekic <bmilekic@FreeBSD.org>
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice unmodified, this list of conditions, and the following
11 * disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
21 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
22 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
23 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
24 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
25 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
26 *
27 * $FreeBSD: releng/6.0/sys/vm/uma_int.h 149074 2005-08-15 09:01:11Z rwatson $
28 *
29 */
30
31 /*
32 * This file includes definitions, structures, prototypes, and inlines that
33 * should not be used outside of the actual implementation of UMA.
34 */
35
36 /*
37 * Here's a quick description of the relationship between the objects:
38 *
39 * Kegs contain lists of slabs which are stored in either the full bin, empty
40 * bin, or partially allocated bin, to reduce fragmentation. They also contain
41 * the user supplied value for size, which is adjusted for alignment purposes
42 * and rsize is the result of that. The Keg also stores information for
43 * managing a hash of page addresses that maps pages to uma_slab_t structures
44 * for pages that don't have embedded uma_slab_t's.
45 *
46 * The uma_slab_t may be embedded in a UMA_SLAB_SIZE chunk of memory or it may
47 * be allocated off the page from a special slab zone. The free list within a
48 * slab is managed with a linked list of indexes, which are 8 bit values. If
49 * UMA_SLAB_SIZE is defined to be too large I will have to switch to 16bit
50 * values. Currently on alpha you can get 250 or so 32 byte items and on x86
51 * you can get 250 or so 16byte items. For item sizes that would yield more
52 * than 10% memory waste we potentially allocate a separate uma_slab_t if this
53 * will improve the number of items per slab that will fit.
54 *
55 * Other potential space optimizations are storing the 8bit of linkage in space
56 * wasted between items due to alignment problems. This may yield a much better
57 * memory footprint for certain sizes of objects. Another alternative is to
58 * increase the UMA_SLAB_SIZE, or allow for dynamic slab sizes. I prefer
59 * dynamic slab sizes because we could stick with 8 bit indexes and only use
60 * large slab sizes for zones with a lot of waste per slab. This may create
61 * ineffeciencies in the vm subsystem due to fragmentation in the address space.
62 *
63 * The only really gross cases, with regards to memory waste, are for those
64 * items that are just over half the page size. You can get nearly 50% waste,
65 * so you fall back to the memory footprint of the power of two allocator. I
66 * have looked at memory allocation sizes on many of the machines available to
67 * me, and there does not seem to be an abundance of allocations at this range
68 * so at this time it may not make sense to optimize for it. This can, of
69 * course, be solved with dynamic slab sizes.
70 *
71 * Kegs may serve multiple Zones but by far most of the time they only serve
72 * one. When a Zone is created, a Keg is allocated and setup for it. While
73 * the backing Keg stores slabs, the Zone caches Buckets of items allocated
74 * from the slabs. Each Zone is equipped with an init/fini and ctor/dtor
75 * pair, as well as with its own set of small per-CPU caches, layered above
76 * the Zone's general Bucket cache.
77 *
78 * The PCPU caches are protected by their own locks, while the Zones backed
79 * by the same Keg all share a common Keg lock (to coalesce contention on
80 * the backing slabs). The backing Keg typically only serves one Zone but
81 * in the case of multiple Zones, one of the Zones is considered the
82 * Master Zone and all Zone-related stats from the Keg are done in the
83 * Master Zone. For an example of a Multi-Zone setup, refer to the
84 * Mbuf allocation code.
85 */
86
87 /*
88 * This is the representation for normal (Non OFFPAGE slab)
89 *
90 * i == item
91 * s == slab pointer
92 *
93 * <---------------- Page (UMA_SLAB_SIZE) ------------------>
94 * ___________________________________________________________
95 * | _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ___________ |
96 * ||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i| |slab header||
97 * ||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_| |___________||
98 * |___________________________________________________________|
99 *
100 *
101 * This is an OFFPAGE slab. These can be larger than UMA_SLAB_SIZE.
102 *
103 * ___________________________________________________________
104 * | _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ |
105 * ||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i||i| |
106 * ||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_||_| |
107 * |___________________________________________________________|
108 * ___________ ^
109 * |slab header| |
110 * |___________|---*
111 *
112 */
113
114 #ifndef VM_UMA_INT_H
115 #define VM_UMA_INT_H
116
117 #define UMA_SLAB_SIZE PAGE_SIZE /* How big are our slabs? */
118 #define UMA_SLAB_MASK (PAGE_SIZE - 1) /* Mask to get back to the page */
119 #define UMA_SLAB_SHIFT PAGE_SHIFT /* Number of bits PAGE_MASK */
120
121 #define UMA_BOOT_PAGES 48 /* Pages allocated for startup */
122
123 /* Max waste before going to off page slab management */
124 #define UMA_MAX_WASTE (UMA_SLAB_SIZE / 10)
125
126 /*
127 * I doubt there will be many cases where this is exceeded. This is the initial
128 * size of the hash table for uma_slabs that are managed off page. This hash
129 * does expand by powers of two. Currently it doesn't get smaller.
130 */
131 #define UMA_HASH_SIZE_INIT 32
132
133 /*
134 * I should investigate other hashing algorithms. This should yield a low
135 * number of collisions if the pages are relatively contiguous.
136 *
137 * This is the same algorithm that most processor caches use.
138 *
139 * I'm shifting and masking instead of % because it should be faster.
140 */
141
142 #define UMA_HASH(h, s) ((((unsigned long)s) >> UMA_SLAB_SHIFT) & \
143 (h)->uh_hashmask)
144
145 #define UMA_HASH_INSERT(h, s, mem) \
146 SLIST_INSERT_HEAD(&(h)->uh_slab_hash[UMA_HASH((h), \
147 (mem))], (s), us_hlink);
148 #define UMA_HASH_REMOVE(h, s, mem) \
149 SLIST_REMOVE(&(h)->uh_slab_hash[UMA_HASH((h), \
150 (mem))], (s), uma_slab, us_hlink);
151
152 /* Hash table for freed address -> slab translation */
153
154 SLIST_HEAD(slabhead, uma_slab);
155
156 struct uma_hash {
157 struct slabhead *uh_slab_hash; /* Hash table for slabs */
158 int uh_hashsize; /* Current size of the hash table */
159 int uh_hashmask; /* Mask used during hashing */
160 };
161
162 /*
163 * Structures for per cpu queues.
164 */
165
166 struct uma_bucket {
167 LIST_ENTRY(uma_bucket) ub_link; /* Link into the zone */
168 int16_t ub_cnt; /* Count of free items. */
169 int16_t ub_entries; /* Max items. */
170 void *ub_bucket[]; /* actual allocation storage */
171 };
172
173 typedef struct uma_bucket * uma_bucket_t;
174
175 struct uma_cache {
176 uma_bucket_t uc_freebucket; /* Bucket we're freeing to */
177 uma_bucket_t uc_allocbucket; /* Bucket to allocate from */
178 u_int64_t uc_allocs; /* Count of allocations */
179 u_int64_t uc_frees; /* Count of frees */
180 };
181
182 typedef struct uma_cache * uma_cache_t;
183
184 /*
185 * Keg management structure
186 *
187 * TODO: Optimize for cache line size
188 *
189 */
190 struct uma_keg {
191 LIST_ENTRY(uma_keg) uk_link; /* List of all kegs */
192
193 struct mtx uk_lock; /* Lock for the keg */
194 struct uma_hash uk_hash;
195
196 LIST_HEAD(,uma_zone) uk_zones; /* Keg's zones */
197 LIST_HEAD(,uma_slab) uk_part_slab; /* partially allocated slabs */
198 LIST_HEAD(,uma_slab) uk_free_slab; /* empty slab list */
199 LIST_HEAD(,uma_slab) uk_full_slab; /* full slabs */
200
201 u_int32_t uk_recurse; /* Allocation recursion count */
202 u_int32_t uk_align; /* Alignment mask */
203 u_int32_t uk_pages; /* Total page count */
204 u_int32_t uk_free; /* Count of items free in slabs */
205 u_int32_t uk_size; /* Requested size of each item */
206 u_int32_t uk_rsize; /* Real size of each item */
207 u_int32_t uk_maxpages; /* Maximum number of pages to alloc */
208
209 uma_init uk_init; /* Keg's init routine */
210 uma_fini uk_fini; /* Keg's fini routine */
211 uma_alloc uk_allocf; /* Allocation function */
212 uma_free uk_freef; /* Free routine */
213
214 struct vm_object *uk_obj; /* Zone specific object */
215 vm_offset_t uk_kva; /* Base kva for zones with objs */
216 uma_zone_t uk_slabzone; /* Slab zone backing us, if OFFPAGE */
217
218 u_int16_t uk_pgoff; /* Offset to uma_slab struct */
219 u_int16_t uk_ppera; /* pages per allocation from backend */
220 u_int16_t uk_ipers; /* Items per slab */
221 u_int32_t uk_flags; /* Internal flags */
222 };
223
224 /* Simpler reference to uma_keg for internal use. */
225 typedef struct uma_keg * uma_keg_t;
226
227 /* Page management structure */
228
229 /* Sorry for the union, but space efficiency is important */
230 struct uma_slab_head {
231 uma_keg_t us_keg; /* Keg we live in */
232 union {
233 LIST_ENTRY(uma_slab) _us_link; /* slabs in zone */
234 unsigned long _us_size; /* Size of allocation */
235 } us_type;
236 SLIST_ENTRY(uma_slab) us_hlink; /* Link for hash table */
237 u_int8_t *us_data; /* First item */
238 u_int8_t us_flags; /* Page flags see uma.h */
239 u_int8_t us_freecount; /* How many are free? */
240 u_int8_t us_firstfree; /* First free item index */
241 };
242
243 /* The standard slab structure */
244 struct uma_slab {
245 struct uma_slab_head us_head; /* slab header data */
246 struct {
247 u_int8_t us_item;
248 } us_freelist[1]; /* actual number bigger */
249 };
250
251 /*
252 * The slab structure for UMA_ZONE_REFCNT zones for whose items we
253 * maintain reference counters in the slab for.
254 */
255 struct uma_slab_refcnt {
256 struct uma_slab_head us_head; /* slab header data */
257 struct {
258 u_int8_t us_item;
259 u_int32_t us_refcnt;
260 } us_freelist[1]; /* actual number bigger */
261 };
262
263 #define us_keg us_head.us_keg
264 #define us_link us_head.us_type._us_link
265 #define us_size us_head.us_type._us_size
266 #define us_hlink us_head.us_hlink
267 #define us_data us_head.us_data
268 #define us_flags us_head.us_flags
269 #define us_freecount us_head.us_freecount
270 #define us_firstfree us_head.us_firstfree
271
272 typedef struct uma_slab * uma_slab_t;
273 typedef struct uma_slab_refcnt * uma_slabrefcnt_t;
274
275 /*
276 * These give us the size of one free item reference within our corresponding
277 * uma_slab structures, so that our calculations during zone setup are correct
278 * regardless of what the compiler decides to do with padding the structure
279 * arrays within uma_slab.
280 */
281 #define UMA_FRITM_SZ (sizeof(struct uma_slab) - sizeof(struct uma_slab_head))
282 #define UMA_FRITMREF_SZ (sizeof(struct uma_slab_refcnt) - \
283 sizeof(struct uma_slab_head))
284
285 /*
286 * Zone management structure
287 *
288 * TODO: Optimize for cache line size
289 *
290 */
291 struct uma_zone {
292 char *uz_name; /* Text name of the zone */
293 struct mtx *uz_lock; /* Lock for the zone (keg's lock) */
294 uma_keg_t uz_keg; /* Our underlying Keg */
295
296 LIST_ENTRY(uma_zone) uz_link; /* List of all zones in keg */
297 LIST_HEAD(,uma_bucket) uz_full_bucket; /* full buckets */
298 LIST_HEAD(,uma_bucket) uz_free_bucket; /* Buckets for frees */
299
300 uma_ctor uz_ctor; /* Constructor for each allocation */
301 uma_dtor uz_dtor; /* Destructor */
302 uma_init uz_init; /* Initializer for each item */
303 uma_fini uz_fini; /* Discards memory */
304
305 u_int64_t uz_allocs; /* Total number of allocations */
306 u_int64_t uz_frees; /* Total number of frees */
307 u_int64_t uz_fails; /* Total number of alloc failures */
308 uint16_t uz_fills; /* Outstanding bucket fills */
309 uint16_t uz_count; /* Highest value ub_ptr can have */
310
311 /*
312 * This HAS to be the last item because we adjust the zone size
313 * based on NCPU and then allocate the space for the zones.
314 */
315 struct uma_cache uz_cpu[1]; /* Per cpu caches */
316 };
317
318 /*
319 * These flags must not overlap with the UMA_ZONE flags specified in uma.h.
320 */
321 #define UMA_ZFLAG_PRIVALLOC 0x10000000 /* Use uz_allocf. */
322 #define UMA_ZFLAG_INTERNAL 0x20000000 /* No offpage no PCPU. */
323 #define UMA_ZFLAG_FULL 0x40000000 /* Reached uz_maxpages */
324 #define UMA_ZFLAG_CACHEONLY 0x80000000 /* Don't ask VM for buckets. */
325
326 #ifdef _KERNEL
327 /* Internal prototypes */
328 static __inline uma_slab_t hash_sfind(struct uma_hash *hash, u_int8_t *data);
329 void *uma_large_malloc(int size, int wait);
330 void uma_large_free(uma_slab_t slab);
331
332 /* Lock Macros */
333
334 #define ZONE_LOCK_INIT(z, lc) \
335 do { \
336 if ((lc)) \
337 mtx_init((z)->uz_lock, (z)->uz_name, \
338 (z)->uz_name, MTX_DEF | MTX_DUPOK); \
339 else \
340 mtx_init((z)->uz_lock, (z)->uz_name, \
341 "UMA zone", MTX_DEF | MTX_DUPOK); \
342 } while (0)
343
344 #define ZONE_LOCK_FINI(z) mtx_destroy((z)->uz_lock)
345 #define ZONE_LOCK(z) mtx_lock((z)->uz_lock)
346 #define ZONE_UNLOCK(z) mtx_unlock((z)->uz_lock)
347
348 /*
349 * Find a slab within a hash table. This is used for OFFPAGE zones to lookup
350 * the slab structure.
351 *
352 * Arguments:
353 * hash The hash table to search.
354 * data The base page of the item.
355 *
356 * Returns:
357 * A pointer to a slab if successful, else NULL.
358 */
359 static __inline uma_slab_t
360 hash_sfind(struct uma_hash *hash, u_int8_t *data)
361 {
362 uma_slab_t slab;
363 int hval;
364
365 hval = UMA_HASH(hash, data);
366
367 SLIST_FOREACH(slab, &hash->uh_slab_hash[hval], us_hlink) {
368 if ((u_int8_t *)slab->us_data == data)
369 return (slab);
370 }
371 return (NULL);
372 }
373
374 static __inline uma_slab_t
375 vtoslab(vm_offset_t va)
376 {
377 vm_page_t p;
378 uma_slab_t slab;
379
380 p = PHYS_TO_VM_PAGE(pmap_kextract(va));
381 slab = (uma_slab_t )p->object;
382
383 if (p->flags & PG_SLAB)
384 return (slab);
385 else
386 return (NULL);
387 }
388
389 static __inline void
390 vsetslab(vm_offset_t va, uma_slab_t slab)
391 {
392 vm_page_t p;
393
394 p = PHYS_TO_VM_PAGE(pmap_kextract(va));
395 p->object = (vm_object_t)slab;
396 p->flags |= PG_SLAB;
397 }
398
399 static __inline void
400 vsetobj(vm_offset_t va, vm_object_t obj)
401 {
402 vm_page_t p;
403
404 p = PHYS_TO_VM_PAGE(pmap_kextract(va));
405 p->object = obj;
406 p->flags &= ~PG_SLAB;
407 }
408
409 /*
410 * The following two functions may be defined by architecture specific code
411 * if they can provide more effecient allocation functions. This is useful
412 * for using direct mapped addresses.
413 */
414 void *uma_small_alloc(uma_zone_t zone, int bytes, u_int8_t *pflag, int wait);
415 void uma_small_free(void *mem, int size, u_int8_t flags);
416 #endif /* _KERNEL */
417
418 #endif /* VM_UMA_INT_H */
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