FreeBSD/Linux Kernel Cross Reference
sys/vm/uma_int.h
1 /*-
2 * Copyright (c) 2002-2005, 2009 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/8.0/sys/vm/uma_int.h 187681 2009-01-25 09:11:24Z jeff $
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 critical sections, and may be accessed
79 * safely only from their associated CPU, while the Zones backed by the same
80 * Keg all share a common Keg lock (to coalesce contention on the backing
81 * slabs). The backing Keg typically only serves one Zone but in the case of
82 * multiple Zones, one of the Zones is considered the Master Zone and all
83 * Zone-related stats from the Keg are done in the Master Zone. For an
84 * example of a Multi-Zone setup, refer to the 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 char *uk_name; /* Name of creating zone. */
197 LIST_HEAD(,uma_zone) uk_zones; /* Keg's zones */
198 LIST_HEAD(,uma_slab) uk_part_slab; /* partially allocated slabs */
199 LIST_HEAD(,uma_slab) uk_free_slab; /* empty slab list */
200 LIST_HEAD(,uma_slab) uk_full_slab; /* full slabs */
201
202 u_int32_t uk_recurse; /* Allocation recursion count */
203 u_int32_t uk_align; /* Alignment mask */
204 u_int32_t uk_pages; /* Total page count */
205 u_int32_t uk_free; /* Count of items free in slabs */
206 u_int32_t uk_size; /* Requested size of each item */
207 u_int32_t uk_rsize; /* Real size of each item */
208 u_int32_t uk_maxpages; /* Maximum number of pages to alloc */
209
210 uma_init uk_init; /* Keg's init routine */
211 uma_fini uk_fini; /* Keg's fini routine */
212 uma_alloc uk_allocf; /* Allocation function */
213 uma_free uk_freef; /* Free routine */
214
215 struct vm_object *uk_obj; /* Zone specific object */
216 vm_offset_t uk_kva; /* Base kva for zones with objs */
217 uma_zone_t uk_slabzone; /* Slab zone backing us, if OFFPAGE */
218
219 u_int16_t uk_pgoff; /* Offset to uma_slab struct */
220 u_int16_t uk_ppera; /* pages per allocation from backend */
221 u_int16_t uk_ipers; /* Items per slab */
222 u_int32_t uk_flags; /* Internal flags */
223 };
224 typedef struct uma_keg * uma_keg_t;
225
226 /* Page management structure */
227
228 /* Sorry for the union, but space efficiency is important */
229 struct uma_slab_head {
230 uma_keg_t us_keg; /* Keg we live in */
231 union {
232 LIST_ENTRY(uma_slab) _us_link; /* slabs in zone */
233 unsigned long _us_size; /* Size of allocation */
234 } us_type;
235 SLIST_ENTRY(uma_slab) us_hlink; /* Link for hash table */
236 u_int8_t *us_data; /* First item */
237 u_int8_t us_flags; /* Page flags see uma.h */
238 u_int8_t us_freecount; /* How many are free? */
239 u_int8_t us_firstfree; /* First free item index */
240 };
241
242 /* The standard slab structure */
243 struct uma_slab {
244 struct uma_slab_head us_head; /* slab header data */
245 struct {
246 u_int8_t us_item;
247 } us_freelist[1]; /* actual number bigger */
248 };
249
250 /*
251 * The slab structure for UMA_ZONE_REFCNT zones for whose items we
252 * maintain reference counters in the slab for.
253 */
254 struct uma_slab_refcnt {
255 struct uma_slab_head us_head; /* slab header data */
256 struct {
257 u_int8_t us_item;
258 u_int32_t us_refcnt;
259 } us_freelist[1]; /* actual number bigger */
260 };
261
262 #define us_keg us_head.us_keg
263 #define us_link us_head.us_type._us_link
264 #define us_size us_head.us_type._us_size
265 #define us_hlink us_head.us_hlink
266 #define us_data us_head.us_data
267 #define us_flags us_head.us_flags
268 #define us_freecount us_head.us_freecount
269 #define us_firstfree us_head.us_firstfree
270
271 typedef struct uma_slab * uma_slab_t;
272 typedef struct uma_slab_refcnt * uma_slabrefcnt_t;
273 typedef uma_slab_t (*uma_slaballoc)(uma_zone_t, uma_keg_t, int);
274
275
276 /*
277 * These give us the size of one free item reference within our corresponding
278 * uma_slab structures, so that our calculations during zone setup are correct
279 * regardless of what the compiler decides to do with padding the structure
280 * arrays within uma_slab.
281 */
282 #define UMA_FRITM_SZ (sizeof(struct uma_slab) - sizeof(struct uma_slab_head))
283 #define UMA_FRITMREF_SZ (sizeof(struct uma_slab_refcnt) - \
284 sizeof(struct uma_slab_head))
285
286 struct uma_klink {
287 LIST_ENTRY(uma_klink) kl_link;
288 uma_keg_t kl_keg;
289 };
290 typedef struct uma_klink *uma_klink_t;
291
292 /*
293 * Zone management structure
294 *
295 * TODO: Optimize for cache line size
296 *
297 */
298 struct uma_zone {
299 char *uz_name; /* Text name of the zone */
300 struct mtx *uz_lock; /* Lock for the zone (keg's lock) */
301
302 LIST_ENTRY(uma_zone) uz_link; /* List of all zones in keg */
303 LIST_HEAD(,uma_bucket) uz_full_bucket; /* full buckets */
304 LIST_HEAD(,uma_bucket) uz_free_bucket; /* Buckets for frees */
305
306 LIST_HEAD(,uma_klink) uz_kegs; /* List of kegs. */
307 struct uma_klink uz_klink; /* klink for first keg. */
308
309 uma_slaballoc uz_slab; /* Allocate a slab from the backend. */
310 uma_ctor uz_ctor; /* Constructor for each allocation */
311 uma_dtor uz_dtor; /* Destructor */
312 uma_init uz_init; /* Initializer for each item */
313 uma_fini uz_fini; /* Discards memory */
314
315 u_int64_t uz_allocs; /* Total number of allocations */
316 u_int64_t uz_frees; /* Total number of frees */
317 u_int64_t uz_fails; /* Total number of alloc failures */
318 u_int32_t uz_flags; /* Flags inherited from kegs */
319 u_int32_t uz_size; /* Size inherited from kegs */
320 uint16_t uz_fills; /* Outstanding bucket fills */
321 uint16_t uz_count; /* Highest value ub_ptr can have */
322
323 /*
324 * This HAS to be the last item because we adjust the zone size
325 * based on NCPU and then allocate the space for the zones.
326 */
327 struct uma_cache uz_cpu[1]; /* Per cpu caches */
328 };
329
330 /*
331 * These flags must not overlap with the UMA_ZONE flags specified in uma.h.
332 */
333 #define UMA_ZFLAG_BUCKET 0x02000000 /* Bucket zone. */
334 #define UMA_ZFLAG_MULTI 0x04000000 /* Multiple kegs in the zone. */
335 #define UMA_ZFLAG_DRAINING 0x08000000 /* Running zone_drain. */
336 #define UMA_ZFLAG_PRIVALLOC 0x10000000 /* Use uz_allocf. */
337 #define UMA_ZFLAG_INTERNAL 0x20000000 /* No offpage no PCPU. */
338 #define UMA_ZFLAG_FULL 0x40000000 /* Reached uz_maxpages */
339 #define UMA_ZFLAG_CACHEONLY 0x80000000 /* Don't ask VM for buckets. */
340
341 #define UMA_ZFLAG_INHERIT (UMA_ZFLAG_INTERNAL | UMA_ZFLAG_CACHEONLY | \
342 UMA_ZFLAG_BUCKET)
343
344 #ifdef _KERNEL
345 /* Internal prototypes */
346 static __inline uma_slab_t hash_sfind(struct uma_hash *hash, u_int8_t *data);
347 void *uma_large_malloc(int size, int wait);
348 void uma_large_free(uma_slab_t slab);
349
350 /* Lock Macros */
351
352 #define KEG_LOCK_INIT(k, lc) \
353 do { \
354 if ((lc)) \
355 mtx_init(&(k)->uk_lock, (k)->uk_name, \
356 (k)->uk_name, MTX_DEF | MTX_DUPOK); \
357 else \
358 mtx_init(&(k)->uk_lock, (k)->uk_name, \
359 "UMA zone", MTX_DEF | MTX_DUPOK); \
360 } while (0)
361
362 #define KEG_LOCK_FINI(k) mtx_destroy(&(k)->uk_lock)
363 #define KEG_LOCK(k) mtx_lock(&(k)->uk_lock)
364 #define KEG_UNLOCK(k) mtx_unlock(&(k)->uk_lock)
365 #define ZONE_LOCK(z) mtx_lock((z)->uz_lock)
366 #define ZONE_UNLOCK(z) mtx_unlock((z)->uz_lock)
367
368 /*
369 * Find a slab within a hash table. This is used for OFFPAGE zones to lookup
370 * the slab structure.
371 *
372 * Arguments:
373 * hash The hash table to search.
374 * data The base page of the item.
375 *
376 * Returns:
377 * A pointer to a slab if successful, else NULL.
378 */
379 static __inline uma_slab_t
380 hash_sfind(struct uma_hash *hash, u_int8_t *data)
381 {
382 uma_slab_t slab;
383 int hval;
384
385 hval = UMA_HASH(hash, data);
386
387 SLIST_FOREACH(slab, &hash->uh_slab_hash[hval], us_hlink) {
388 if ((u_int8_t *)slab->us_data == data)
389 return (slab);
390 }
391 return (NULL);
392 }
393
394 static __inline uma_slab_t
395 vtoslab(vm_offset_t va)
396 {
397 vm_page_t p;
398 uma_slab_t slab;
399
400 p = PHYS_TO_VM_PAGE(pmap_kextract(va));
401 slab = (uma_slab_t )p->object;
402
403 if (p->flags & PG_SLAB)
404 return (slab);
405 else
406 return (NULL);
407 }
408
409 static __inline void
410 vsetslab(vm_offset_t va, uma_slab_t slab)
411 {
412 vm_page_t p;
413
414 p = PHYS_TO_VM_PAGE(pmap_kextract(va));
415 p->object = (vm_object_t)slab;
416 p->flags |= PG_SLAB;
417 }
418
419 static __inline void
420 vsetobj(vm_offset_t va, vm_object_t obj)
421 {
422 vm_page_t p;
423
424 p = PHYS_TO_VM_PAGE(pmap_kextract(va));
425 p->object = obj;
426 p->flags &= ~PG_SLAB;
427 }
428
429 /*
430 * The following two functions may be defined by architecture specific code
431 * if they can provide more effecient allocation functions. This is useful
432 * for using direct mapped addresses.
433 */
434 void *uma_small_alloc(uma_zone_t zone, int bytes, u_int8_t *pflag, int wait);
435 void uma_small_free(void *mem, int size, u_int8_t flags);
436 #endif /* _KERNEL */
437
438 #endif /* VM_UMA_INT_H */
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