struct hti *next;
unsigned scale;
int max_probe;
- int references;
+ int ref_count;
int count; // TODO: make these counters distributed
int num_entries_copied;
int copy_scan;
const datatype_t *key_type;
};
-static const map_val_t COPIED_VALUE = -1;
+static const map_val_t COPIED_VALUE = TAG_VALUE(DOES_NOT_EXIST, TAG1);
static const map_val_t TOMBSTONE = STRIP_TAG(-1, TAG1);
static const unsigned ENTRIES_PER_BUCKET = CACHE_LINE_SIZE/sizeof(entry_t);
}
hti->ht = parent;
+ hti->ref_count = 1; // one for the parent
assert(hti->scale >= MIN_SCALE && hti->scale < 63); // size must be a power of 2
assert(sizeof(entry_t) * ENTRIES_PER_BUCKET % CACHE_LINE_SIZE == 0); // divisible into cache
#endif
map_val_t ht1_ent_val = ht1_ent->val;
- if (EXPECT_FALSE(ht1_ent_val == COPIED_VALUE)) {
+ if (EXPECT_FALSE(ht1_ent_val == COPIED_VALUE || ht1_ent_val == TAG_VALUE(TOMBSTONE, TAG1))) {
TRACE("h1", "hti_copy_entry: entry %p already copied to table %p", ht1_ent, ht2);
return FALSE; // already copied
}
TRACE("h1", "hti_copy_entry: empty entry %p killed", ht1_ent, 0);
return TRUE;
}
- if (ht1_ent_val == COPIED_VALUE) {
- TRACE("h0", "hti_copy_entry: lost race to kill empty entry %p; the entry is already killed", ht1_ent, 0);
- return FALSE; // another thread beat us to it
- }
TRACE("h0", "hti_copy_entry: lost race to kill empty entry %p; the entry is not empty", ht1_ent, 0);
}
// Tag the value in the old entry to indicate a copy is in progress.
ht1_ent_val = SYNC_FETCH_AND_OR(&ht1_ent->val, TAG_VALUE(0, TAG1));
TRACE("h2", "hti_copy_entry: tagged the value %p in old entry %p", ht1_ent_val, ht1_ent);
- if (ht1_ent_val == COPIED_VALUE) {
+ if (ht1_ent_val == COPIED_VALUE || ht1_ent_val == TAG_VALUE(TOMBSTONE, TAG1)) {
TRACE("h1", "hti_copy_entry: entry %p already copied to table %p", ht1_ent, ht2);
return FALSE; // <value> was already copied by another thread.
}
+ // The old table's dead entries don't need to be copied to the new table
+ if (ht1_ent_val == TOMBSTONE)
+ return TRUE;
+
// Install the key in the new table.
map_key_t ht1_ent_key = ht1_ent->key;
map_key_t key = (ht1->ht->key_type == NULL) ? (map_key_t)ht1_ent_key : (map_key_t)GET_PTR(ht1_ent_key);
- // The old table's dead entries don't need to be copied to the new table, but their keys need to be freed.
- assert(COPIED_VALUE == TAG_VALUE(TOMBSTONE, TAG1));
- if (ht1_ent_val == TOMBSTONE) {
- TRACE("h1", "hti_copy_entry: entry %p old value was deleted, now freeing key %p", ht1_ent, key);
- if (EXPECT_FALSE(ht1->ht->key_type != NULL)) {
- nbd_defer_free((void *)key);
- }
- return TRUE;
- }
-
// We use 0 to indicate that <key_hash> is uninitiallized. Occasionally the key's hash will really be 0 and we
- // waste time recomputing it every time. It is rare enough (1 in 65k) that it won't hurt performance.
+ // waste time recomputing it every time. It is rare enough that it won't hurt performance.
if (key_hash == 0) {
key_hash = (ht1->ht->key_type == NULL)
? murmur32_8b(ht1_ent_key)
map_key_t new_key = (hti->ht->key_type == NULL)
? (map_key_t)key
: (map_key_t)hti->ht->key_type->clone((void *)key);
+#ifndef NBD32
if (EXPECT_FALSE(hti->ht->key_type != NULL)) {
// Combine <new_key> pointer with bits from its hash
new_key = ((uint64_t)(key_hash >> 16) << 48) | new_key;
}
+#endif
// CAS the key into the table.
map_key_t old_ent_key = SYNC_CAS(&ent->key, DOES_NOT_EXIST, new_key);
// If the entry is in the middle of a copy, the copy must be completed first.
map_val_t ent_val = ent->val;
if (EXPECT_FALSE(IS_TAGGED(ent_val, TAG1))) {
- if (ent_val != COPIED_VALUE) {
+ if (ent_val != COPIED_VALUE && ent_val != TAG_VALUE(TOMBSTONE, TAG1)) {
int did_copy = hti_copy_entry(hti, ent, key_hash, ((volatile hti_t *)hti)->next);
if (did_copy) {
SYNC_ADD(&hti->num_entries_copied, 1);
// If the entry is being copied, finish the copy and retry on the next table.
map_val_t ent_val = ent->val;
if (EXPECT_FALSE(IS_TAGGED(ent_val, TAG1))) {
- if (EXPECT_FALSE(ent_val != COPIED_VALUE)) {
+ if (EXPECT_FALSE(ent_val != COPIED_VALUE && ent_val != TAG_VALUE(TOMBSTONE, TAG1))) {
int did_copy = hti_copy_entry(hti, ent, key_hash, ((volatile hti_t *)hti)->next);
if (did_copy) {
SYNC_ADD(&hti->num_entries_copied, 1);
}
// returns TRUE if copy is done
-int hti_help_copy (hti_t *hti) {
+static int hti_help_copy (hti_t *hti) {
volatile entry_t *ent;
size_t limit;
size_t total_copied = hti->num_entries_copied;
return (total_copied == (1 << hti->scale));
}
+static void hti_defer_free (hti_t *hti) {
+ assert(hti->ref_count == 0);
+
+ for (uint32_t i = 0; i < (1 << hti->scale); ++i) {
+ map_key_t key = hti->table[i].key;
+ map_val_t val = hti->table[i].val;
+ if (val == COPIED_VALUE)
+ continue;
+ assert(!IS_TAGGED(val, TAG1) || val == TAG_VALUE(TOMBSTONE, TAG1)); // copy not in progress
+ if (hti->ht->key_type != NULL && key != DOES_NOT_EXIST) {
+ nbd_defer_free(GET_PTR(key));
+ }
+ }
+ nbd_defer_free((void *)hti->table);
+ nbd_defer_free(hti);
+}
+
+static void hti_release (hti_t *hti) {
+ assert(hti->ref_count > 0);
+ int ref_count = SYNC_ADD(&hti->ref_count, -1);
+ if (ref_count == 0) {
+ hti_defer_free(hti);
+ }
+}
+
//
map_val_t ht_cas (hashtable_t *ht, map_key_t key, map_val_t expected_val, map_val_t new_val) {
if (EXPECT_FALSE(hti->next != NULL)) {
int done = hti_help_copy(hti);
- // Dispose of fully copied tables.
- if (done && hti->references == 0) {
-
- int r = SYNC_CAS(&hti->references, 0, -1);
- if (r == 0) {
- assert(hti->next);
- if (SYNC_CAS(&ht->hti, hti, hti->next) == hti) {
- nbd_defer_free((void *)hti->table);
- nbd_defer_free(hti);
- }
+ // Unlink fully copied tables.
+ if (done) {
+ assert(hti->next);
+ if (SYNC_CAS(&ht->hti, hti, hti->next) == hti) {
+ hti_release(hti);
}
}
}
void ht_free (hashtable_t *ht) {
hti_t *hti = ht->hti;
do {
- for (uint32_t i = 0; i < (1 << hti->scale); ++i) {
- assert(hti->table[i].val == COPIED_VALUE || !IS_TAGGED(hti->table[i].val, TAG1));
- if (ht->key_type != NULL && hti->table[i].key != DOES_NOT_EXIST) {
- nbd_free(GET_PTR(hti->table[i].key));
- }
- }
hti_t *next = hti->next;
- nbd_free((void *)hti->table);
- nbd_free(hti);
+ assert(hti->ref_count == 1);
+ hti_release(hti);
hti = next;
} while (hti);
nbd_free(ht);
}
ht_iter_t *ht_iter_begin (hashtable_t *ht, map_key_t key) {
- hti_t *hti = ht->hti;
- int rcount;
+ hti_t *hti;
+ int ref_count;
do {
- while (((volatile hti_t *)hti)->next != NULL) {
+ hti = ht->hti;
+ while (hti->next != NULL) {
do { } while (hti_help_copy(hti) != TRUE);
hti = hti->next;
}
-
- int old = hti->references;
do {
- rcount = old;
- if (rcount != -1) {
- old = SYNC_CAS(&hti->references, rcount, rcount + 1);
- }
- } while (rcount != old);
- } while (rcount == -1);
+ ref_count = hti->ref_count;
+ if(ref_count == 0)
+ break;
+ } while (ref_count != SYNC_CAS(&hti->ref_count, ref_count, ref_count + 1));
+ } while (ref_count == 0);
ht_iter_t *iter = nbd_malloc(sizeof(ht_iter_t));
iter->hti = hti;
}
void ht_iter_free (ht_iter_t *iter) {
- SYNC_ADD(&iter->hti->references, -1);
+ hti_release(iter->hti);
nbd_free(iter);
}
projects / nbds / blobdiff