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dict.c improvements to rehashing and reallocation.

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This commit is contained in:
antirez 2016-09-07 12:06:07 +02:00
parent 96224f750f
commit 9554fd5ab0
1 changed files with 21 additions and 6 deletions
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27
src/dict.c
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@ -147,13 +147,26 @@ unsigned int dictGenCaseHashFunction(const unsigned char *buf, int len) {
/* ----------------------------- API implementation ------------------------- */
dictEntry *dictPushEntry(dictEntryVector **table, unsigned int idx, const void *key, const void *val, unsigned int hash)
/* Push a new entry in a vector of entries, taking care of allocating or
* reallocating the vector if needed. If 'orig_entries' is non zero it
* means that we are moving entries in the course of rehashing to a bigger
* table, from a vector that had 'orig_entires' entries. The function can
* use this hint to make better reallocation choices. */
dictEntry *dictPushEntry(dictEntryVector **table, unsigned int idx, const void *key, const void *val, unsigned int hash, uint32_t orig_entries)
{
dictEntryVector *dv = table[idx];
dictEntry *he;
if (dv == NULL) {
int initlen = dict_resize_ratio/4;
int initlen;
if (orig_entries) {
/* If we are rehashing to a larger table, in the average this
* slot will take orig_entries/2 slots, assuming the new table
* is double in size. */
initlen = orig_entries/2;
} else {
initlen = dict_resize_ratio/4;
}
if (initlen == 0) initlen = 1;
dv = table[idx] =
zcalloc(sizeof(dictEntryVector)+sizeof(dictEntry)*initlen);
@ -161,7 +174,7 @@ dictEntry *dictPushEntry(dictEntryVector **table, unsigned int idx, const void *
dv->free = initlen-1;
he = dv->entry;
} else if (dv->free == 0) {
int newlen = (dv->used+dv->free)*2;
int newlen = dv->used*2;
dv = table[idx] = zrealloc(table[idx],sizeof(dictEntryVector)+sizeof(dictEntry)*newlen);
he = dv->entry+dv->used;
dv->used++;
@ -279,6 +292,7 @@ int dictExpandToOptimalSize(dict *d, unsigned long entries) {
int dictRehash(dict *d, int n) {
int empty_visits = n*10; /* Max number of empty buckets to visit. */
if (!dictIsRehashing(d)) return 0;
int to_smaller = d->ht[0].size > d->ht[1].size; /* Moving to smaller tab? */
while(n-- && d->ht[0].used != 0) {
dictEntryVector *dv;
@ -297,6 +311,7 @@ int dictRehash(dict *d, int n) {
* to the next, since all the entries of this table will hash into
* the same slot of the target table. */
uint32_t entries = dv ? (dv->used + dv->free) : 0;
uint32_t entries_hint = to_smaller ? 0 : entries;
uint32_t j;
for (j = 0; j < entries; j++) {
@ -304,9 +319,9 @@ int dictRehash(dict *d, int n) {
/* Get the index in the new hash table */
if (dv->entry[j].key == NULL) continue;
h = dictHashKey(d, dv->entry[j].key) & d->ht[1].sizemask;
h = dv->entry[j].hash & d->ht[1].sizemask;
dictPushEntry(d->ht[1].table,h,dv->entry[j].key,dv->entry[j].v.val,
dv->entry[j].hash);
dv->entry[j].hash, entries_hint);
d->ht[1].used++;
d->ht[0].used--;
}
@ -401,7 +416,7 @@ dictEntry *dictAddRaw(dict *d, void *key)
/* Store the new entry: if we are rehashing all new entries go to
* the new table. */
ht = dictIsRehashing(d) ? &d->ht[1] : &d->ht[0];
entry = dictPushEntry(ht->table,index,key,NULL,hash);
entry = dictPushEntry(ht->table,index,key,NULL,hash,0);
ht->used++;
return entry;
}