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/sc.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 */
29extern size_t sz_pind2sz_tab[SC_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 */
34extern size_t sz_index2size_tab[SC_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 */
40extern uint8_t sz_size2index_tab[];
41
42static const size_t sz_large_pad =
43#ifdef JEMALLOC_CACHE_OBLIVIOUS
44 PAGE
45#else
46 0
47#endif
48 ;
49
50extern void sz_boot(const sc_data_t *sc_data);
51
52JEMALLOC_ALWAYS_INLINE pszind_t
53sz_psz2ind(size_t psz) {
54 if (unlikely(psz > SC_LARGE_MAXCLASS)) {
55 return SC_NPSIZES;
56 }
57 pszind_t x = lg_floor((psz<<1)-1);
58 pszind_t shift = (x < SC_LG_NGROUP + LG_PAGE) ?
59 0 : x - (SC_LG_NGROUP + LG_PAGE);
60 pszind_t grp = shift << SC_LG_NGROUP;
61
62 pszind_t lg_delta = (x < SC_LG_NGROUP + LG_PAGE + 1) ?
63 LG_PAGE : x - SC_LG_NGROUP - 1;
64
65 size_t delta_inverse_mask = ZU(-1) << lg_delta;
66 pszind_t mod = ((((psz-1) & delta_inverse_mask) >> lg_delta)) &
67 ((ZU(1) << SC_LG_NGROUP) - 1);
68
69 pszind_t ind = grp + mod;
70 return ind;
71}
72
73static inline size_t
74sz_pind2sz_compute(pszind_t pind) {
75 if (unlikely(pind == SC_NPSIZES)) {
76 return SC_LARGE_MAXCLASS + PAGE;
77 }
78 size_t grp = pind >> SC_LG_NGROUP;
79 size_t mod = pind & ((ZU(1) << SC_LG_NGROUP) - 1);
80
81 size_t grp_size_mask = ~((!!grp)-1);
82 size_t grp_size = ((ZU(1) << (LG_PAGE + (SC_LG_NGROUP-1))) << grp)
83 & grp_size_mask;
84
85 size_t shift = (grp == 0) ? 1 : grp;
86 size_t lg_delta = shift + (LG_PAGE-1);
87 size_t mod_size = (mod+1) << lg_delta;
88
89 size_t sz = grp_size + mod_size;
90 return sz;
91}
92
93static inline size_t
94sz_pind2sz_lookup(pszind_t pind) {
95 size_t ret = (size_t)sz_pind2sz_tab[pind];
96 assert(ret == sz_pind2sz_compute(pind));
97 return ret;
98}
99
100static inline size_t
101sz_pind2sz(pszind_t pind) {
102 assert(pind < SC_NPSIZES + 1);
103 return sz_pind2sz_lookup(pind);
104}
105
106static inline size_t
107sz_psz2u(size_t psz) {
108 if (unlikely(psz > SC_LARGE_MAXCLASS)) {
109 return SC_LARGE_MAXCLASS + PAGE;
110 }
111 size_t x = lg_floor((psz<<1)-1);
112 size_t lg_delta = (x < SC_LG_NGROUP + LG_PAGE + 1) ?
113 LG_PAGE : x - SC_LG_NGROUP - 1;
114 size_t delta = ZU(1) << lg_delta;
115 size_t delta_mask = delta - 1;
116 size_t usize = (psz + delta_mask) & ~delta_mask;
117 return usize;
118}
119
120static inline szind_t
121sz_size2index_compute(size_t size) {
122 if (unlikely(size > SC_LARGE_MAXCLASS)) {
123 return SC_NSIZES;
124 }
125
126 if (size == 0) {
127 return 0;
128 }
129#if (SC_NTINY != 0)
130 if (size <= (ZU(1) << SC_LG_TINY_MAXCLASS)) {
131 szind_t lg_tmin = SC_LG_TINY_MAXCLASS - SC_NTINY + 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 < SC_LG_NGROUP + LG_QUANTUM) ? 0 :
139 x - (SC_LG_NGROUP + LG_QUANTUM);
140 szind_t grp = shift << SC_LG_NGROUP;
141
142 szind_t lg_delta = (x < SC_LG_NGROUP + LG_QUANTUM + 1)
143 ? LG_QUANTUM : x - SC_LG_NGROUP - 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) << SC_LG_NGROUP) - 1);
148
149 szind_t index = SC_NTINY + grp + mod;
150 return index;
151 }
152}
153
154JEMALLOC_ALWAYS_INLINE szind_t
155sz_size2index_lookup(size_t size) {
156 assert(size <= SC_LOOKUP_MAXCLASS);
157 szind_t ret = (sz_size2index_tab[(size + (ZU(1) << SC_LG_TINY_MIN) - 1)
158 >> SC_LG_TINY_MIN]);
159 assert(ret == sz_size2index_compute(size));
160 return ret;
161}
162
163JEMALLOC_ALWAYS_INLINE szind_t
164sz_size2index(size_t size) {
165 if (likely(size <= SC_LOOKUP_MAXCLASS)) {
166 return sz_size2index_lookup(size);
167 }
168 return sz_size2index_compute(size);
169}
170
171static inline size_t
172sz_index2size_compute(szind_t index) {
173#if (SC_NTINY > 0)
174 if (index < SC_NTINY) {
175 return (ZU(1) << (SC_LG_TINY_MAXCLASS - SC_NTINY + 1 + index));
176 }
177#endif
178 {
179 size_t reduced_index = index - SC_NTINY;
180 size_t grp = reduced_index >> SC_LG_NGROUP;
181 size_t mod = reduced_index & ((ZU(1) << SC_LG_NGROUP) -
182 1);
183
184 size_t grp_size_mask = ~((!!grp)-1);
185 size_t grp_size = ((ZU(1) << (LG_QUANTUM +
186 (SC_LG_NGROUP-1))) << grp) & grp_size_mask;
187
188 size_t shift = (grp == 0) ? 1 : grp;
189 size_t lg_delta = shift + (LG_QUANTUM-1);
190 size_t mod_size = (mod+1) << lg_delta;
191
192 size_t usize = grp_size + mod_size;
193 return usize;
194 }
195}
196
197JEMALLOC_ALWAYS_INLINE size_t
198sz_index2size_lookup(szind_t index) {
199 size_t ret = (size_t)sz_index2size_tab[index];
200 assert(ret == sz_index2size_compute(index));
201 return ret;
202}
203
204JEMALLOC_ALWAYS_INLINE size_t
205sz_index2size(szind_t index) {
206 assert(index < SC_NSIZES);
207 return sz_index2size_lookup(index);
208}
209
210JEMALLOC_ALWAYS_INLINE size_t
211sz_s2u_compute(size_t size) {
212 if (unlikely(size > SC_LARGE_MAXCLASS)) {
213 return 0;
214 }
215
216 if (size == 0) {
217 size++;
218 }
219#if (SC_NTINY > 0)
220 if (size <= (ZU(1) << SC_LG_TINY_MAXCLASS)) {
221 size_t lg_tmin = SC_LG_TINY_MAXCLASS - SC_NTINY + 1;
222 size_t lg_ceil = lg_floor(pow2_ceil_zu(size));
223 return (lg_ceil < lg_tmin ? (ZU(1) << lg_tmin) :
224 (ZU(1) << lg_ceil));
225 }
226#endif
227 {
228 size_t x = lg_floor((size<<1)-1);
229 size_t lg_delta = (x < SC_LG_NGROUP + LG_QUANTUM + 1)
230 ? LG_QUANTUM : x - SC_LG_NGROUP - 1;
231 size_t delta = ZU(1) << lg_delta;
232 size_t delta_mask = delta - 1;
233 size_t usize = (size + delta_mask) & ~delta_mask;
234 return usize;
235 }
236}
237
238JEMALLOC_ALWAYS_INLINE size_t
239sz_s2u_lookup(size_t size) {
240 size_t ret = sz_index2size_lookup(sz_size2index_lookup(size));
241
242 assert(ret == sz_s2u_compute(size));
243 return ret;
244}
245
246/*
247 * Compute usable size that would result from allocating an object with the
248 * specified size.
249 */
250JEMALLOC_ALWAYS_INLINE size_t
251sz_s2u(size_t size) {
252 if (likely(size <= SC_LOOKUP_MAXCLASS)) {
253 return sz_s2u_lookup(size);
254 }
255 return sz_s2u_compute(size);
256}
257
258/*
259 * Compute usable size that would result from allocating an object with the
260 * specified size and alignment.
261 */
262JEMALLOC_ALWAYS_INLINE size_t
263sz_sa2u(size_t size, size_t alignment) {
264 size_t usize;
265
266 assert(alignment != 0 && ((alignment - 1) & alignment) == 0);
267
268 /* Try for a small size class. */
269 if (size <= SC_SMALL_MAXCLASS && alignment < PAGE) {
270 /*
271 * Round size up to the nearest multiple of alignment.
272 *
273 * This done, we can take advantage of the fact that for each
274 * small size class, every object is aligned at the smallest
275 * power of two that is non-zero in the base two representation
276 * of the size. For example:
277 *
278 * Size | Base 2 | Minimum alignment
279 * -----+----------+------------------
280 * 96 | 1100000 | 32
281 * 144 | 10100000 | 32
282 * 192 | 11000000 | 64
283 */
284 usize = sz_s2u(ALIGNMENT_CEILING(size, alignment));
285 if (usize < SC_LARGE_MINCLASS) {
286 return usize;
287 }
288 }
289
290 /* Large size class. Beware of overflow. */
291
292 if (unlikely(alignment > SC_LARGE_MAXCLASS)) {
293 return 0;
294 }
295
296 /* Make sure result is a large size class. */
297 if (size <= SC_LARGE_MINCLASS) {
298 usize = SC_LARGE_MINCLASS;
299 } else {
300 usize = sz_s2u(size);
301 if (usize < size) {
302 /* size_t overflow. */
303 return 0;
304 }
305 }
306
307 /*
308 * Calculate the multi-page mapping that large_palloc() would need in
309 * order to guarantee the alignment.
310 */
311 if (usize + sz_large_pad + PAGE_CEILING(alignment) - PAGE < usize) {
312 /* size_t overflow. */
313 return 0;
314 }
315 return usize;
316}
317
318#endif /* JEMALLOC_INTERNAL_SIZE_H */
319