1 #ifndef JEMALLOC_INTERNAL_SIZE_H
2 #define JEMALLOC_INTERNAL_SIZE_H
3
4 #include "jemalloc/internal/bit_util.h"
5 #include "jemalloc/internal/pages.h"
6 #include "jemalloc/internal/size_classes.h"
7 #include "jemalloc/internal/util.h"
8
9 /*
10 * sz module: Size computations.
11 *
12 * Some abbreviations used here:
13 * p: Page
14 * ind: Index
15 * s, sz: Size
16 * u: Usable size
17 * a: Aligned
18 *
19 * These are not always used completely consistently, but should be enough to
20 * interpret function names. E.g. sz_psz2ind converts page size to page size
21 * index; sz_sa2u converts a (size, alignment) allocation request to the usable
22 * size that would result from such an allocation.
23 */
24
25 /*
26 * sz_pind2sz_tab encodes the same information as could be computed by
27 * sz_pind2sz_compute().
28 */
29 extern size_t const sz_pind2sz_tab[NPSIZES+1];
30 /*
31 * sz_index2size_tab encodes the same information as could be computed (at
32 * unacceptable cost in some code paths) by sz_index2size_compute().
33 */
34 extern size_t const sz_index2size_tab[NSIZES];
35 /*
36 * sz_size2index_tab is a compact lookup table that rounds request sizes up to
37 * size classes. In order to reduce cache footprint, the table is compressed,
38 * and all accesses are via sz_size2index().
39 */
40 extern uint8_t const sz_size2index_tab[];
41
42 static const size_t sz_large_pad =
43 #ifdef JEMALLOC_CACHE_OBLIVIOUS
44 PAGE
45 #else
46 0
47 #endif
48 ;
49
50 JEMALLOC_ALWAYS_INLINE pszind_t
sz_psz2ind(size_t psz)51 sz_psz2ind(size_t psz) {
52 if (unlikely(psz > LARGE_MAXCLASS)) {
53 return NPSIZES;
54 }
55 {
56 pszind_t x = lg_floor((psz<<1)-1);
57 pszind_t shift = (x < LG_SIZE_CLASS_GROUP + LG_PAGE) ? 0 : x -
58 (LG_SIZE_CLASS_GROUP + LG_PAGE);
59 pszind_t grp = shift << LG_SIZE_CLASS_GROUP;
60
61 pszind_t lg_delta = (x < LG_SIZE_CLASS_GROUP + LG_PAGE + 1) ?
62 LG_PAGE : x - LG_SIZE_CLASS_GROUP - 1;
63
64 size_t delta_inverse_mask = ZU(-1) << lg_delta;
65 pszind_t mod = ((((psz-1) & delta_inverse_mask) >> lg_delta)) &
66 ((ZU(1) << LG_SIZE_CLASS_GROUP) - 1);
67
68 pszind_t ind = grp + mod;
69 return ind;
70 }
71 }
72
73 static inline size_t
sz_pind2sz_compute(pszind_t pind)74 sz_pind2sz_compute(pszind_t pind) {
75 if (unlikely(pind == NPSIZES)) {
76 return LARGE_MAXCLASS + PAGE;
77 }
78 {
79 size_t grp = pind >> LG_SIZE_CLASS_GROUP;
80 size_t mod = pind & ((ZU(1) << LG_SIZE_CLASS_GROUP) - 1);
81
82 size_t grp_size_mask = ~((!!grp)-1);
83 size_t grp_size = ((ZU(1) << (LG_PAGE +
84 (LG_SIZE_CLASS_GROUP-1))) << grp) & grp_size_mask;
85
86 size_t shift = (grp == 0) ? 1 : grp;
87 size_t lg_delta = shift + (LG_PAGE-1);
88 size_t mod_size = (mod+1) << lg_delta;
89
90 size_t sz = grp_size + mod_size;
91 return sz;
92 }
93 }
94
95 static inline size_t
sz_pind2sz_lookup(pszind_t pind)96 sz_pind2sz_lookup(pszind_t pind) {
97 size_t ret = (size_t)sz_pind2sz_tab[pind];
98 assert(ret == sz_pind2sz_compute(pind));
99 return ret;
100 }
101
102 static inline size_t
sz_pind2sz(pszind_t pind)103 sz_pind2sz(pszind_t pind) {
104 assert(pind < NPSIZES+1);
105 return sz_pind2sz_lookup(pind);
106 }
107
108 static inline size_t
sz_psz2u(size_t psz)109 sz_psz2u(size_t psz) {
110 if (unlikely(psz > LARGE_MAXCLASS)) {
111 return LARGE_MAXCLASS + PAGE;
112 }
113 {
114 size_t x = lg_floor((psz<<1)-1);
115 size_t lg_delta = (x < LG_SIZE_CLASS_GROUP + LG_PAGE + 1) ?
116 LG_PAGE : x - LG_SIZE_CLASS_GROUP - 1;
117 size_t delta = ZU(1) << lg_delta;
118 size_t delta_mask = delta - 1;
119 size_t usize = (psz + delta_mask) & ~delta_mask;
120 return usize;
121 }
122 }
123
124 static inline szind_t
sz_size2index_compute(size_t size)125 sz_size2index_compute(size_t size) {
126 if (unlikely(size > LARGE_MAXCLASS)) {
127 return NSIZES;
128 }
129 #if (NTBINS != 0)
130 if (size <= (ZU(1) << LG_TINY_MAXCLASS)) {
131 szind_t lg_tmin = LG_TINY_MAXCLASS - NTBINS + 1;
132 szind_t lg_ceil = lg_floor(pow2_ceil_zu(size));
133 return (lg_ceil < lg_tmin ? 0 : lg_ceil - lg_tmin);
134 }
135 #endif
136 {
137 szind_t x = lg_floor((size<<1)-1);
138 szind_t shift = (x < LG_SIZE_CLASS_GROUP + LG_QUANTUM) ? 0 :
139 x - (LG_SIZE_CLASS_GROUP + LG_QUANTUM);
140 szind_t grp = shift << LG_SIZE_CLASS_GROUP;
141
142 szind_t lg_delta = (x < LG_SIZE_CLASS_GROUP + LG_QUANTUM + 1)
143 ? LG_QUANTUM : x - LG_SIZE_CLASS_GROUP - 1;
144
145 size_t delta_inverse_mask = ZU(-1) << lg_delta;
146 szind_t mod = ((((size-1) & delta_inverse_mask) >> lg_delta)) &
147 ((ZU(1) << LG_SIZE_CLASS_GROUP) - 1);
148
149 szind_t index = NTBINS + grp + mod;
150 return index;
151 }
152 }
153
154 JEMALLOC_ALWAYS_INLINE szind_t
sz_size2index_lookup(size_t size)155 sz_size2index_lookup(size_t size) {
156 assert(size <= LOOKUP_MAXCLASS);
157 {
158 szind_t ret = (sz_size2index_tab[(size-1) >> LG_TINY_MIN]);
159 assert(ret == sz_size2index_compute(size));
160 return ret;
161 }
162 }
163
164 JEMALLOC_ALWAYS_INLINE szind_t
sz_size2index(size_t size)165 sz_size2index(size_t size) {
166 assert(size > 0);
167 if (likely(size <= LOOKUP_MAXCLASS)) {
168 return sz_size2index_lookup(size);
169 }
170 return sz_size2index_compute(size);
171 }
172
173 static inline size_t
sz_index2size_compute(szind_t index)174 sz_index2size_compute(szind_t index) {
175 #if (NTBINS > 0)
176 if (index < NTBINS) {
177 return (ZU(1) << (LG_TINY_MAXCLASS - NTBINS + 1 + index));
178 }
179 #endif
180 {
181 size_t reduced_index = index - NTBINS;
182 size_t grp = reduced_index >> LG_SIZE_CLASS_GROUP;
183 size_t mod = reduced_index & ((ZU(1) << LG_SIZE_CLASS_GROUP) -
184 1);
185
186 size_t grp_size_mask = ~((!!grp)-1);
187 size_t grp_size = ((ZU(1) << (LG_QUANTUM +
188 (LG_SIZE_CLASS_GROUP-1))) << grp) & grp_size_mask;
189
190 size_t shift = (grp == 0) ? 1 : grp;
191 size_t lg_delta = shift + (LG_QUANTUM-1);
192 size_t mod_size = (mod+1) << lg_delta;
193
194 size_t usize = grp_size + mod_size;
195 return usize;
196 }
197 }
198
199 JEMALLOC_ALWAYS_INLINE size_t
sz_index2size_lookup(szind_t index)200 sz_index2size_lookup(szind_t index) {
201 size_t ret = (size_t)sz_index2size_tab[index];
202 assert(ret == sz_index2size_compute(index));
203 return ret;
204 }
205
206 JEMALLOC_ALWAYS_INLINE size_t
sz_index2size(szind_t index)207 sz_index2size(szind_t index) {
208 assert(index < NSIZES);
209 return sz_index2size_lookup(index);
210 }
211
212 JEMALLOC_ALWAYS_INLINE size_t
sz_s2u_compute(size_t size)213 sz_s2u_compute(size_t size) {
214 if (unlikely(size > LARGE_MAXCLASS)) {
215 return 0;
216 }
217 #if (NTBINS > 0)
218 if (size <= (ZU(1) << LG_TINY_MAXCLASS)) {
219 size_t lg_tmin = LG_TINY_MAXCLASS - NTBINS + 1;
220 size_t lg_ceil = lg_floor(pow2_ceil_zu(size));
221 return (lg_ceil < lg_tmin ? (ZU(1) << lg_tmin) :
222 (ZU(1) << lg_ceil));
223 }
224 #endif
225 {
226 size_t x = lg_floor((size<<1)-1);
227 size_t lg_delta = (x < LG_SIZE_CLASS_GROUP + LG_QUANTUM + 1)
228 ? LG_QUANTUM : x - LG_SIZE_CLASS_GROUP - 1;
229 size_t delta = ZU(1) << lg_delta;
230 size_t delta_mask = delta - 1;
231 size_t usize = (size + delta_mask) & ~delta_mask;
232 return usize;
233 }
234 }
235
236 JEMALLOC_ALWAYS_INLINE size_t
sz_s2u_lookup(size_t size)237 sz_s2u_lookup(size_t size) {
238 size_t ret = sz_index2size_lookup(sz_size2index_lookup(size));
239
240 assert(ret == sz_s2u_compute(size));
241 return ret;
242 }
243
244 /*
245 * Compute usable size that would result from allocating an object with the
246 * specified size.
247 */
248 JEMALLOC_ALWAYS_INLINE size_t
sz_s2u(size_t size)249 sz_s2u(size_t size) {
250 assert(size > 0);
251 if (likely(size <= LOOKUP_MAXCLASS)) {
252 return sz_s2u_lookup(size);
253 }
254 return sz_s2u_compute(size);
255 }
256
257 /*
258 * Compute usable size that would result from allocating an object with the
259 * specified size and alignment.
260 */
261 JEMALLOC_ALWAYS_INLINE size_t
sz_sa2u(size_t size,size_t alignment)262 sz_sa2u(size_t size, size_t alignment) {
263 size_t usize;
264
265 assert(alignment != 0 && ((alignment - 1) & alignment) == 0);
266
267 /* Try for a small size class. */
268 if (size <= SMALL_MAXCLASS && alignment < PAGE) {
269 /*
270 * Round size up to the nearest multiple of alignment.
271 *
272 * This done, we can take advantage of the fact that for each
273 * small size class, every object is aligned at the smallest
274 * power of two that is non-zero in the base two representation
275 * of the size. For example:
276 *
277 * Size | Base 2 | Minimum alignment
278 * -----+----------+------------------
279 * 96 | 1100000 | 32
280 * 144 | 10100000 | 32
281 * 192 | 11000000 | 64
282 */
283 usize = sz_s2u(ALIGNMENT_CEILING(size, alignment));
284 if (usize < LARGE_MINCLASS) {
285 return usize;
286 }
287 }
288
289 /* Large size class. Beware of overflow. */
290
291 if (unlikely(alignment > LARGE_MAXCLASS)) {
292 return 0;
293 }
294
295 /* Make sure result is a large size class. */
296 if (size <= LARGE_MINCLASS) {
297 usize = LARGE_MINCLASS;
298 } else {
299 usize = sz_s2u(size);
300 if (usize < size) {
301 /* size_t overflow. */
302 return 0;
303 }
304 }
305
306 /*
307 * Calculate the multi-page mapping that large_palloc() would need in
308 * order to guarantee the alignment.
309 */
310 if (usize + sz_large_pad + PAGE_CEILING(alignment) - PAGE < usize) {
311 /* size_t overflow. */
312 return 0;
313 }
314 return usize;
315 }
316
317 #endif /* JEMALLOC_INTERNAL_SIZE_H */
318