3 * A mostly concurrent hashtable
6 * Rodrigo Kumpera (kumpera@gmail.com)
11 #include "mono-conc-hashtable.h"
12 #include <mono/utils/hazard-pointer.h>
14 /* Configuration knobs. */
16 #define INITIAL_SIZE 32
17 #define LOAD_FACTOR 0.75f
18 #define TOMBSTONE ((gpointer)(ssize_t)-1)
30 struct _MonoConcurrentHashTable {
31 volatile conc_table *table; /* goes to HP0 */
33 GEqualFunc equal_func;
36 GDestroyNotify key_destroy_func;
37 GDestroyNotify value_destroy_func;
41 conc_table_new (int size)
43 conc_table *res = g_new (conc_table, 1);
44 res->table_size = size;
45 res->kvs = g_new0 (key_value_pair, size);
50 conc_table_free (gpointer ptr)
52 conc_table *table = (conc_table *)ptr;
58 conc_table_lf_free (conc_table *table)
60 mono_thread_hazardous_try_free (table, conc_table_free);
65 A common problem with power of two hashtables is that it leads of bad clustering when dealing
68 The solution here is to mix the bits from two primes plus the hash itself, it produces a better spread
69 than just the numbers.
72 static MONO_ALWAYS_INLINE int
75 return ((hash * 215497) >> 16) ^ (hash * 1823231 + hash);
78 static MONO_ALWAYS_INLINE void
79 insert_one_local (conc_table *table, GHashFunc hash_func, gpointer key, gpointer value)
81 key_value_pair *kvs = table->kvs;
82 int table_mask = table->table_size - 1;
83 int hash = mix_hash (hash_func (key));
84 int i = hash & table_mask;
86 while (table->kvs [i].key)
87 i = (i + 1) & table_mask;
90 kvs [i].value = value;
93 /* LOCKING: Must be called holding hash_table->mutex */
95 expand_table (MonoConcurrentHashTable *hash_table)
97 conc_table *old_table = (conc_table*)hash_table->table;
98 conc_table *new_table = conc_table_new (old_table->table_size * 2);
99 key_value_pair *kvs = old_table->kvs;
102 for (i = 0; i < old_table->table_size; ++i) {
103 if (kvs [i].key && kvs [i].key != TOMBSTONE)
104 insert_one_local (new_table, hash_table->hash_func, kvs [i].key, kvs [i].value);
106 mono_memory_barrier ();
107 hash_table->table = new_table;
108 hash_table->overflow_count = (int)(new_table->table_size * LOAD_FACTOR);
109 conc_table_lf_free (old_table);
113 MonoConcurrentHashTable*
114 mono_conc_hashtable_new (GHashFunc hash_func, GEqualFunc key_equal_func)
116 MonoConcurrentHashTable *res = g_new0 (MonoConcurrentHashTable, 1);
117 res->hash_func = hash_func ? hash_func : g_direct_hash;
118 res->equal_func = key_equal_func;
119 // res->equal_func = g_direct_equal;
120 res->table = conc_table_new (INITIAL_SIZE);
121 res->element_count = 0;
122 res->overflow_count = (int)(INITIAL_SIZE * LOAD_FACTOR);
126 MonoConcurrentHashTable*
127 mono_conc_hashtable_new_full (GHashFunc hash_func, GEqualFunc key_equal_func, GDestroyNotify key_destroy_func, GDestroyNotify value_destroy_func)
129 MonoConcurrentHashTable *res = mono_conc_hashtable_new (hash_func, key_equal_func);
130 res->key_destroy_func = key_destroy_func;
131 res->value_destroy_func = value_destroy_func;
137 mono_conc_hashtable_destroy (MonoConcurrentHashTable *hash_table)
139 if (hash_table->key_destroy_func || hash_table->value_destroy_func) {
141 conc_table *table = (conc_table*)hash_table->table;
142 key_value_pair *kvs = table->kvs;
144 for (i = 0; i < table->table_size; ++i) {
145 if (kvs [i].key && kvs [i].key != TOMBSTONE) {
146 if (hash_table->key_destroy_func)
147 (hash_table->key_destroy_func) (kvs [i].key);
148 if (hash_table->value_destroy_func)
149 (hash_table->value_destroy_func) (kvs [i].value);
153 conc_table_free ((gpointer)hash_table->table);
158 mono_conc_hashtable_lookup (MonoConcurrentHashTable *hash_table, gpointer key)
160 MonoThreadHazardPointers* hp;
162 int hash, i, table_mask;
164 hash = mix_hash (hash_table->hash_func (key));
165 hp = mono_hazard_pointer_get ();
168 table = (conc_table *)mono_get_hazardous_pointer ((gpointer volatile*)&hash_table->table, hp, 0);
169 table_mask = table->table_size - 1;
171 i = hash & table_mask;
173 if (G_LIKELY (!hash_table->equal_func)) {
174 while (kvs [i].key) {
175 if (key == kvs [i].key) {
177 /* The read of keys must happen before the read of values */
178 mono_memory_barrier ();
179 value = kvs [i].value;
180 /* FIXME check for NULL if we add suppport for removal */
181 mono_hazard_pointer_clear (hp, 0);
184 i = (i + 1) & table_mask;
187 GEqualFunc equal = hash_table->equal_func;
189 while (kvs [i].key) {
190 if (kvs [i].key != TOMBSTONE && equal (key, kvs [i].key)) {
192 /* The read of keys must happen before the read of values */
193 mono_memory_barrier ();
194 value = kvs [i].value;
196 /* We just read a value been deleted, try again. */
197 if (G_UNLIKELY (!value))
200 mono_hazard_pointer_clear (hp, 0);
203 i = (i + 1) & table_mask;
207 /* The table might have expanded and the value is now on the newer table */
208 mono_memory_barrier ();
209 if (hash_table->table != table)
212 mono_hazard_pointer_clear (hp, 0);
217 * mono_conc_hashtable_remove:
218 * Remove a value from the hashtable. Requires external locking
219 * \returns the old value if \p key is already present or NULL
222 mono_conc_hashtable_remove (MonoConcurrentHashTable *hash_table, gpointer key)
226 int hash, i, table_mask;
228 g_assert (key != NULL && key != TOMBSTONE);
230 hash = mix_hash (hash_table->hash_func (key));
232 table = (conc_table*)hash_table->table;
234 table_mask = table->table_size - 1;
235 i = hash & table_mask;
237 if (!hash_table->equal_func) {
240 return NULL; /*key not found*/
243 if (key == kvs [i].key) {
244 gpointer value = kvs [i].value;
245 kvs [i].value = NULL;
246 mono_memory_barrier ();
247 kvs [i].key = TOMBSTONE;
248 --hash_table->element_count;
250 if (hash_table->key_destroy_func != NULL)
251 (*hash_table->key_destroy_func) (key);
252 if (hash_table->value_destroy_func != NULL)
253 (*hash_table->value_destroy_func) (value);
257 i = (i + 1) & table_mask;
260 GEqualFunc equal = hash_table->equal_func;
263 return NULL; /*key not found*/
266 if (kvs [i].key != TOMBSTONE && equal (key, kvs [i].key)) {
267 gpointer old_key = kvs [i].key;
268 gpointer value = kvs [i].value;
269 kvs [i].value = NULL;
270 mono_memory_barrier ();
271 kvs [i].key = TOMBSTONE;
273 if (hash_table->key_destroy_func != NULL)
274 (*hash_table->key_destroy_func) (old_key);
275 if (hash_table->value_destroy_func != NULL)
276 (*hash_table->value_destroy_func) (value);
280 i = (i + 1) & table_mask;
285 * mono_conc_hashtable_insert:
286 * Insert a value into the hashtable. Requires external locking.
287 * \returns the old value if \p key is already present or NULL
290 mono_conc_hashtable_insert (MonoConcurrentHashTable *hash_table, gpointer key, gpointer value)
294 int hash, i, table_mask;
296 g_assert (key != NULL && key != TOMBSTONE);
297 g_assert (value != NULL);
299 hash = mix_hash (hash_table->hash_func (key));
301 if (hash_table->element_count >= hash_table->overflow_count)
302 expand_table (hash_table);
304 table = (conc_table*)hash_table->table;
306 table_mask = table->table_size - 1;
307 i = hash & table_mask;
309 if (!hash_table->equal_func) {
311 if (!kvs [i].key || kvs [i].key == TOMBSTONE) {
312 kvs [i].value = value;
313 /* The write to values must happen after the write to keys */
314 mono_memory_barrier ();
316 ++hash_table->element_count;
319 if (key == kvs [i].key) {
320 gpointer value = kvs [i].value;
323 i = (i + 1) & table_mask;
326 GEqualFunc equal = hash_table->equal_func;
328 if (!kvs [i].key || kvs [i].key == TOMBSTONE) {
329 kvs [i].value = value;
330 /* The write to values must happen after the write to keys */
331 mono_memory_barrier ();
333 ++hash_table->element_count;
336 if (equal (key, kvs [i].key)) {
337 gpointer value = kvs [i].value;
340 i = (i + 1) & table_mask;
346 * mono_conc_hashtable_foreach:
347 * Calls \p func for each value in the hashtable. Requires external locking.
350 mono_conc_hashtable_foreach (MonoConcurrentHashTable *hash_table, GHFunc func, gpointer userdata)
353 conc_table *table = (conc_table*)hash_table->table;
354 key_value_pair *kvs = table->kvs;
356 for (i = 0; i < table->table_size; ++i) {
357 if (kvs [i].key && kvs [i].key != TOMBSTONE) {
358 func (kvs [i].key, kvs [i].value, userdata);
364 * mono_conc_hashtable_foreach_steal:
366 * Calls @func for each entry in the hashtable, if @func returns true, remove from the hashtable. Requires external locking.
367 * Same semantics as g_hash_table_foreach_steal.
370 mono_conc_hashtable_foreach_steal (MonoConcurrentHashTable *hash_table, GHRFunc func, gpointer userdata)
373 conc_table *table = (conc_table*)hash_table->table;
374 key_value_pair *kvs = table->kvs;
376 for (i = 0; i < table->table_size; ++i) {
377 if (kvs [i].key && kvs [i].key != TOMBSTONE) {
378 if (func (kvs [i].key, kvs [i].value, userdata)) {
379 kvs [i].value = NULL;
380 mono_memory_barrier ();
381 kvs [i].key = TOMBSTONE;
382 --hash_table->element_count;