cd415dbde91934c6ff2c79ad410bce97e3582183
[lttng-tools.git] / src / common / hashtable / rculfhash-mm-mmap.c
1 /*
2 * rculfhash-mm-mmap.c
3 *
4 * mmap/reservation based memory management for Lock-Free RCU Hash Table
5 *
6 * Copyright 2011 - Lai Jiangshan <laijs@cn.fujitsu.com>
7 *
8 * This library is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * This library is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with this library; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23 #define _GNU_SOURCE
24 #define _LGPL_SOURCE
25 #include <unistd.h>
26 #include <sys/mman.h>
27 #include "rculfhash-internal.h"
28
29 #ifndef MAP_ANONYMOUS
30 #define MAP_ANONYMOUS MAP_ANON
31 #endif
32
33 /* reserve inaccessible memory space without allocation any memory */
34 static void *memory_map(size_t length)
35 {
36 void *ret = mmap(NULL, length, PROT_NONE,
37 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
38
39 assert(ret != MAP_FAILED);
40 return ret;
41 }
42
43 static void memory_unmap(void *ptr, size_t length)
44 {
45 int ret __attribute__((unused));
46
47 ret = munmap(ptr, length);
48
49 assert(ret == 0);
50 }
51
52 static void memory_populate(void *ptr, size_t length)
53 {
54 void *ret __attribute__((unused));
55
56 ret = mmap(ptr, length, PROT_READ | PROT_WRITE,
57 MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
58
59 assert(ret == ptr);
60 }
61
62 /*
63 * Discard garbage memory and avoid system save it when try to swap it out.
64 * Make it still reserved, inaccessible.
65 */
66 static void memory_discard(void *ptr, size_t length)
67 {
68 void *ret __attribute__((unused));
69
70 ret = mmap(ptr, length, PROT_NONE,
71 MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
72
73 assert(ret == ptr);
74 }
75
76 static
77 void cds_lfht_alloc_bucket_table(struct cds_lfht *ht, unsigned long order)
78 {
79 if (order == 0) {
80 if (ht->min_nr_alloc_buckets == ht->max_nr_buckets) {
81 /* small table */
82 ht->tbl_mmap = calloc(ht->max_nr_buckets,
83 sizeof(*ht->tbl_mmap));
84 assert(ht->tbl_mmap);
85 return;
86 }
87 /* large table */
88 ht->tbl_mmap = memory_map(ht->max_nr_buckets
89 * sizeof(*ht->tbl_mmap));
90 memory_populate(ht->tbl_mmap,
91 ht->min_nr_alloc_buckets * sizeof(*ht->tbl_mmap));
92 } else if (order > ht->min_alloc_buckets_order) {
93 /* large table */
94 unsigned long len = 1UL << (order - 1);
95
96 assert(ht->min_nr_alloc_buckets < ht->max_nr_buckets);
97 memory_populate(ht->tbl_mmap + len,
98 len * sizeof(*ht->tbl_mmap));
99 }
100 /* Nothing to do for 0 < order && order <= ht->min_alloc_buckets_order */
101 }
102
103 /*
104 * cds_lfht_free_bucket_table() should be called with decreasing order.
105 * When cds_lfht_free_bucket_table(0) is called, it means the whole
106 * lfht is destroyed.
107 */
108 static
109 void cds_lfht_free_bucket_table(struct cds_lfht *ht, unsigned long order)
110 {
111 if (order == 0) {
112 if (ht->min_nr_alloc_buckets == ht->max_nr_buckets) {
113 /* small table */
114 poison_free(ht->tbl_mmap);
115 return;
116 }
117 /* large table */
118 memory_unmap(ht->tbl_mmap,
119 ht->max_nr_buckets * sizeof(*ht->tbl_mmap));
120 } else if (order > ht->min_alloc_buckets_order) {
121 /* large table */
122 unsigned long len = 1UL << (order - 1);
123
124 assert(ht->min_nr_alloc_buckets < ht->max_nr_buckets);
125 memory_discard(ht->tbl_mmap + len, len * sizeof(*ht->tbl_mmap));
126 }
127 /* Nothing to do for 0 < order && order <= ht->min_alloc_buckets_order */
128 }
129
130 static
131 struct cds_lfht_node *bucket_at(struct cds_lfht *ht, unsigned long index)
132 {
133 return &ht->tbl_mmap[index];
134 }
135
136 static
137 struct cds_lfht *alloc_cds_lfht(unsigned long min_nr_alloc_buckets,
138 unsigned long max_nr_buckets)
139 {
140 unsigned long page_bucket_size;
141
142 page_bucket_size = getpagesize() / sizeof(struct cds_lfht_node);
143 if (max_nr_buckets <= page_bucket_size) {
144 /* small table */
145 min_nr_alloc_buckets = max_nr_buckets;
146 } else {
147 /* large table */
148 min_nr_alloc_buckets = max(min_nr_alloc_buckets,
149 page_bucket_size);
150 }
151
152 return __default_alloc_cds_lfht(
153 &cds_lfht_mm_mmap, sizeof(struct cds_lfht),
154 min_nr_alloc_buckets, max_nr_buckets);
155 }
156
157 const struct cds_lfht_mm_type cds_lfht_mm_mmap = {
158 .alloc_cds_lfht = alloc_cds_lfht,
159 .alloc_bucket_table = cds_lfht_alloc_bucket_table,
160 .free_bucket_table = cds_lfht_free_bucket_table,
161 .bucket_at = bucket_at,
162 };
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