liblttng-ht/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 #include <unistd.h>
  24 #include <sys/mman.h>
  25 #include "rculfhash-internal.h"
  26
  27 /* reserve inaccessible memory space without allocation any memory */
  28 static void *memory_map(size_t length)
  29 {
  30         void *ret = mmap(NULL, length, PROT_NONE,
  31                         MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
  32
  33         assert(ret != MAP_FAILED);
  34         return ret;
  35 }
  36
  37 static void memory_unmap(void *ptr, size_t length)
  38 {
  39         int ret __attribute__((unused));
  40
  41         ret = munmap(ptr, length);
  42
  43         assert(ret == 0);
  44 }
  45
  46 static void memory_populate(void *ptr, size_t length)
  47 {
  48         void *ret __attribute__((unused));
  49
  50         ret = mmap(ptr, length, PROT_READ | PROT_WRITE,
  51                         MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
  52
  53         assert(ret == ptr);
  54 }
  55
  56 /*
  57  * Discard garbage memory and avoid system save it when try to swap it out.
  58  * Make it still reserved, inaccessible.
  59  */
  60 static void memory_discard(void *ptr, size_t length)
  61 {
  62         void *ret __attribute__((unused));
  63
  64         ret = mmap(ptr, length, PROT_NONE,
  65                         MAP_FIXED | MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
  66
  67         assert(ret == ptr);
  68 }
  69
  70 static
  71 void cds_lfht_alloc_bucket_table(struct cds_lfht *ht, unsigned long order)
  72 {
  73         if (order == 0) {
  74                 if (ht->min_nr_alloc_buckets == ht->max_nr_buckets) {
  75                         /* small table */
  76                         ht->tbl_mmap = calloc(ht->max_nr_buckets,
  77                                         sizeof(*ht->tbl_mmap));
  78                         assert(ht->tbl_mmap);
  79                         return;
  80                 }
  81                 /* large table */
  82                 ht->tbl_mmap = memory_map(ht->max_nr_buckets
  83                         * sizeof(*ht->tbl_mmap));
  84                 memory_populate(ht->tbl_mmap,
  85                         ht->min_nr_alloc_buckets * sizeof(*ht->tbl_mmap));
  86         } else if (order > ht->min_alloc_buckets_order) {
  87                 /* large table */
  88                 unsigned long len = 1UL << (order - 1);
  89
  90                 assert(ht->min_nr_alloc_buckets < ht->max_nr_buckets);
  91                 memory_populate(ht->tbl_mmap + len,
  92                                 len * sizeof(*ht->tbl_mmap));
  93         }
  94         /* Nothing to do for 0 < order && order <= ht->min_alloc_buckets_order */
  95 }
  96
  97 /*
  98  * cds_lfht_free_bucket_table() should be called with decreasing order.
  99  * When cds_lfht_free_bucket_table(0) is called, it means the whole
 100  * lfht is destroyed.
 101  */
 102 static
 103 void cds_lfht_free_bucket_table(struct cds_lfht *ht, unsigned long order)
 104 {
 105         if (order == 0) {
 106                 if (ht->min_nr_alloc_buckets == ht->max_nr_buckets) {
 107                         /* small table */
 108                         poison_free(ht->tbl_mmap);
 109                         return;
 110                 }
 111                 /* large table */
 112                 memory_unmap(ht->tbl_mmap,
 113                         ht->max_nr_buckets * sizeof(*ht->tbl_mmap));
 114         } else if (order > ht->min_alloc_buckets_order) {
 115                 /* large table */
 116                 unsigned long len = 1UL << (order - 1);
 117
 118                 assert(ht->min_nr_alloc_buckets < ht->max_nr_buckets);
 119                 memory_discard(ht->tbl_mmap + len, len * sizeof(*ht->tbl_mmap));
 120         }
 121         /* Nothing to do for 0 < order && order <= ht->min_alloc_buckets_order */
 122 }
 123
 124 static
 125 struct cds_lfht_node *bucket_at(struct cds_lfht *ht, unsigned long index)
 126 {
 127         return &ht->tbl_mmap[index];
 128 }
 129
 130 static
 131 struct cds_lfht *alloc_cds_lfht(unsigned long min_nr_alloc_buckets,
 132                 unsigned long max_nr_buckets)
 133 {
 134         unsigned long page_bucket_size;
 135
 136         page_bucket_size = getpagesize() / sizeof(struct cds_lfht_node);
 137         if (max_nr_buckets <= page_bucket_size) {
 138                 /* small table */
 139                 min_nr_alloc_buckets = max_nr_buckets;
 140         } else {
 141                 /* large table */
 142                 min_nr_alloc_buckets = max(min_nr_alloc_buckets,
 143                                         page_bucket_size);
 144         }
 145
 146         return __default_alloc_cds_lfht(
 147                         &cds_lfht_mm_mmap, sizeof(struct cds_lfht),
 148                         min_nr_alloc_buckets, max_nr_buckets);
 149 }
 150
 151 const struct cds_lfht_mm_type cds_lfht_mm_mmap = {
 152         .alloc_cds_lfht = alloc_cds_lfht,
 153         .alloc_bucket_table = cds_lfht_alloc_bucket_table,
 154         .free_bucket_table = cds_lfht_free_bucket_table,
 155         .bucket_at = bucket_at,
 156 };