X-Git-Url: https://git.saurik.com/redis.git/blobdiff_plain/dae121d9aa38626db9962ff02879b55eb7ca36bf..97224de7f962f8c39cb357969f83378d12d25f96:/dict.c diff --git a/dict.c b/dict.c index 150a0e3d..d5010708 100644 --- a/dict.c +++ b/dict.c @@ -41,6 +41,7 @@ #include #include #include +#include #include "dict.h" #include "zmalloc.h" @@ -119,7 +120,7 @@ unsigned int dictGenHashFunction(const unsigned char *buf, int len) { /* Reset an hashtable already initialized with ht_init(). * NOTE: This function should only called by ht_destroy(). */ -static void _dictReset(dict *ht) +static void _dictReset(dictht *ht) { ht->table = NULL; ht->size = 0; @@ -131,105 +132,167 @@ static void _dictReset(dict *ht) dict *dictCreate(dictType *type, void *privDataPtr) { - dict *ht = _dictAlloc(sizeof(*ht)); + dict *d = _dictAlloc(sizeof(*d)); - _dictInit(ht,type,privDataPtr); - return ht; + _dictInit(d,type,privDataPtr); + return d; } /* Initialize the hash table */ -int _dictInit(dict *ht, dictType *type, +int _dictInit(dict *d, dictType *type, void *privDataPtr) { - _dictReset(ht); - ht->type = type; - ht->privdata = privDataPtr; + _dictReset(&d->ht[0]); + _dictReset(&d->ht[1]); + d->type = type; + d->privdata = privDataPtr; + d->rehashidx = -1; + d->iterators = 0; return DICT_OK; } /* Resize the table to the minimal size that contains all the elements, * but with the invariant of a USER/BUCKETS ration near to <= 1 */ -int dictResize(dict *ht) +int dictResize(dict *d) { - int minimal = ht->used; + int minimal; - if (!dict_can_resize) return DICT_ERR; + if (!dict_can_resize || dictIsRehashing(d)) return DICT_ERR; + minimal = d->ht[0].used; if (minimal < DICT_HT_INITIAL_SIZE) minimal = DICT_HT_INITIAL_SIZE; - return dictExpand(ht, minimal); + return dictExpand(d, minimal); } /* Expand or create the hashtable */ -int dictExpand(dict *ht, unsigned long size) +int dictExpand(dict *d, unsigned long size) { - dict n; /* the new hashtable */ - unsigned long realsize = _dictNextPower(size), i; + dictht n; /* the new hashtable */ + unsigned long realsize = _dictNextPower(size); /* the size is invalid if it is smaller than the number of * elements already inside the hashtable */ - if (ht->used > size) + if (dictIsRehashing(d) || d->ht[0].used > size) return DICT_ERR; - _dictInit(&n, ht->type, ht->privdata); n.size = realsize; n.sizemask = realsize-1; n.table = _dictAlloc(realsize*sizeof(dictEntry*)); + n.used = 0; /* Initialize all the pointers to NULL */ memset(n.table, 0, realsize*sizeof(dictEntry*)); - /* Copy all the elements from the old to the new table: - * note that if the old hash table is empty ht->size is zero, - * so dictExpand just creates an hash table. */ - n.used = ht->used; - for (i = 0; i < ht->size && ht->used > 0; i++) { - dictEntry *he, *nextHe; + /* Is this the first initialization? If so it's not really a rehashing + * we just set the first hash table so that it can accept keys. */ + if (d->ht[0].table == NULL) { + d->ht[0] = n; + return DICT_OK; + } - if (ht->table[i] == NULL) continue; - - /* For each hash entry on this slot... */ - he = ht->table[i]; - while(he) { + /* Prepare a second hash table for incremental rehashing */ + d->ht[1] = n; + d->rehashidx = 0; + return DICT_OK; +} + +/* Performs N steps of incremental rehashing. Returns 1 if there are still + * keys to move from the old to the new hash table, otherwise 0 is returned. + * Note that a rehashing step consists in moving a bucket (that may have more + * thank one key as we use chaining) from the old to the new hash table. */ +int dictRehash(dict *d, int n) { + if (!dictIsRehashing(d)) return 0; + + while(n--) { + dictEntry *de, *nextde; + + /* Check if we already rehashed the whole table... */ + if (d->ht[0].used == 0) { + _dictFree(d->ht[0].table); + d->ht[0] = d->ht[1]; + _dictReset(&d->ht[1]); + d->rehashidx = -1; + return 0; + } + + /* Note that rehashidx can't overflow as we are sure there are more + * elements because ht[0].used != 0 */ + while(d->ht[0].table[d->rehashidx] == NULL) d->rehashidx++; + de = d->ht[0].table[d->rehashidx]; + /* Move all the keys in this bucket from the old to the new hash HT */ + while(de) { unsigned int h; - nextHe = he->next; - /* Get the new element index */ - h = dictHashKey(ht, he->key) & n.sizemask; - he->next = n.table[h]; - n.table[h] = he; - ht->used--; - /* Pass to the next element */ - he = nextHe; + nextde = de->next; + /* Get the index in the new hash table */ + h = dictHashKey(d, de->key) & d->ht[1].sizemask; + de->next = d->ht[1].table[h]; + d->ht[1].table[h] = de; + d->ht[0].used--; + d->ht[1].used++; + de = nextde; } + d->ht[0].table[d->rehashidx] = NULL; + d->rehashidx++; } - assert(ht->used == 0); - _dictFree(ht->table); + return 1; +} - /* Remap the new hashtable in the old */ - *ht = n; - return DICT_OK; +long long timeInMilliseconds(void) { + struct timeval tv; + + gettimeofday(&tv,NULL); + return (((long long)tv.tv_sec)*1000)+(tv.tv_usec/1000); +} + +/* Rehash for an amount of time between ms milliseconds and ms+1 milliseconds */ +int dictRehashMilliseconds(dict *d, int ms) { + long long start = timeInMilliseconds(); + int rehashes = 0; + + while(dictRehash(d,100)) { + rehashes += 100; + if (timeInMilliseconds()-start > ms) break; + } + return rehashes; +} + +/* This function performs just a step of rehashing, and only if there are + * not iterators bound to our hash table. When we have iterators in the middle + * of a rehashing we can't mess with the two hash tables otherwise some element + * can be missed or duplicated. + * + * This function is called by common lookup or update operations in the + * dictionary so that the hash table automatically migrates from H1 to H2 + * while it is actively used. */ +static void _dictRehashStep(dict *d) { + if (d->iterators == 0) dictRehash(d,1); } /* Add an element to the target hash table */ -int dictAdd(dict *ht, void *key, void *val) +int dictAdd(dict *d, void *key, void *val) { int index; dictEntry *entry; + dictht *ht; + + if (dictIsRehashing(d)) _dictRehashStep(d); /* Get the index of the new element, or -1 if * the element already exists. */ - if ((index = _dictKeyIndex(ht, key)) == -1) + if ((index = _dictKeyIndex(d, key)) == -1) return DICT_ERR; /* Allocates the memory and stores key */ + ht = dictIsRehashing(d) ? &d->ht[1] : &d->ht[0]; entry = _dictAlloc(sizeof(*entry)); entry->next = ht->table[index]; ht->table[index] = entry; + ht->used++; /* Set the hash entry fields. */ - dictSetHashKey(ht, entry, key); - dictSetHashVal(ht, entry, val); - ht->used++; + dictSetHashKey(d, entry, key); + dictSetHashVal(d, entry, val); return DICT_OK; } @@ -237,16 +300,16 @@ int dictAdd(dict *ht, void *key, void *val) * Return 1 if the key was added from scratch, 0 if there was already an * element with such key and dictReplace() just performed a value update * operation. */ -int dictReplace(dict *ht, void *key, void *val) +int dictReplace(dict *d, void *key, void *val) { dictEntry *entry, auxentry; /* Try to add the element. If the key * does not exists dictAdd will suceed. */ - if (dictAdd(ht, key, val) == DICT_OK) + if (dictAdd(d, key, val) == DICT_OK) return 1; /* It already exists, get the entry */ - entry = dictFind(ht, key); + entry = dictFind(d, key); /* Free the old value and set the new one */ /* Set the new value and free the old one. Note that it is important * to do that in this order, as the value may just be exactly the same @@ -254,40 +317,45 @@ int dictReplace(dict *ht, void *key, void *val) * you want to increment (set), and then decrement (free), and not the * reverse. */ auxentry = *entry; - dictSetHashVal(ht, entry, val); - dictFreeEntryVal(ht, &auxentry); + dictSetHashVal(d, entry, val); + dictFreeEntryVal(d, &auxentry); return 0; } /* Search and remove an element */ -static int dictGenericDelete(dict *ht, const void *key, int nofree) +static int dictGenericDelete(dict *d, const void *key, int nofree) { - unsigned int h; + unsigned int h, idx; dictEntry *he, *prevHe; + int table; - if (ht->size == 0) - return DICT_ERR; - h = dictHashKey(ht, key) & ht->sizemask; - he = ht->table[h]; + if (d->ht[0].size == 0) return DICT_ERR; /* d->ht[0].table is NULL */ + if (dictIsRehashing(d)) _dictRehashStep(d); + h = dictHashKey(d, key); - prevHe = NULL; - while(he) { - if (dictCompareHashKeys(ht, key, he->key)) { - /* Unlink the element from the list */ - if (prevHe) - prevHe->next = he->next; - else - ht->table[h] = he->next; - if (!nofree) { - dictFreeEntryKey(ht, he); - dictFreeEntryVal(ht, he); + for (table = 0; table <= 1; table++) { + idx = h & d->ht[table].sizemask; + he = d->ht[table].table[idx]; + prevHe = NULL; + while(he) { + if (dictCompareHashKeys(d, key, he->key)) { + /* Unlink the element from the list */ + if (prevHe) + prevHe->next = he->next; + else + d->ht[table].table[idx] = he->next; + if (!nofree) { + dictFreeEntryKey(d, he); + dictFreeEntryVal(d, he); + } + _dictFree(he); + d->ht[table].used--; + return DICT_OK; } - _dictFree(he); - ht->used--; - return DICT_OK; + prevHe = he; + he = he->next; } - prevHe = he; - he = he->next; + if (!dictIsRehashing(d)) break; } return DICT_ERR; /* not found */ } @@ -300,8 +368,8 @@ int dictDeleteNoFree(dict *ht, const void *key) { return dictGenericDelete(ht,key,1); } -/* Destroy an entire hash table */ -int _dictClear(dict *ht) +/* Destroy an entire dictionary */ +int _dictClear(dict *d, dictht *ht) { unsigned long i; @@ -312,8 +380,8 @@ int _dictClear(dict *ht) if ((he = ht->table[i]) == NULL) continue; while(he) { nextHe = he->next; - dictFreeEntryKey(ht, he); - dictFreeEntryVal(ht, he); + dictFreeEntryKey(d, he); + dictFreeEntryVal(d, he); _dictFree(he); ht->used--; he = nextHe; @@ -327,33 +395,47 @@ int _dictClear(dict *ht) } /* Clear & Release the hash table */ -void dictRelease(dict *ht) +void dictRelease(dict *d) { - _dictClear(ht); - _dictFree(ht); + _dictClear(d,&d->ht[0]); + _dictClear(d,&d->ht[1]); + _dictFree(d); } -dictEntry *dictFind(dict *ht, const void *key) +dictEntry *dictFind(dict *d, const void *key) { dictEntry *he; - unsigned int h; - - if (ht->size == 0) return NULL; - h = dictHashKey(ht, key) & ht->sizemask; - he = ht->table[h]; - while(he) { - if (dictCompareHashKeys(ht, key, he->key)) - return he; - he = he->next; + unsigned int h, idx, table; + + if (d->ht[0].size == 0) return NULL; /* We don't have a table at all */ + if (dictIsRehashing(d)) _dictRehashStep(d); + h = dictHashKey(d, key); + for (table = 0; table <= 1; table++) { + idx = h & d->ht[table].sizemask; + he = d->ht[table].table[idx]; + while(he) { + if (dictCompareHashKeys(d, key, he->key)) + return he; + he = he->next; + } + if (!dictIsRehashing(d)) return NULL; } return NULL; } -dictIterator *dictGetIterator(dict *ht) +void *dictFetchValue(dict *d, const void *key) { + dictEntry *he; + + he = dictFind(d,key); + return he ? dictGetEntryVal(he) : NULL; +} + +dictIterator *dictGetIterator(dict *d) { dictIterator *iter = _dictAlloc(sizeof(*iter)); - iter->ht = ht; + iter->d = d; + iter->table = 0; iter->index = -1; iter->entry = NULL; iter->nextEntry = NULL; @@ -364,10 +446,19 @@ dictEntry *dictNext(dictIterator *iter) { while (1) { if (iter->entry == NULL) { + dictht *ht = &iter->d->ht[iter->table]; + if (iter->index == -1 && iter->table == 0) iter->d->iterators++; iter->index++; - if (iter->index >= - (signed)iter->ht->size) break; - iter->entry = iter->ht->table[iter->index]; + if (iter->index >= (signed) ht->size) { + if (dictIsRehashing(iter->d) && iter->table == 0) { + iter->table++; + iter->index = 0; + ht = &iter->d->ht[1]; + } else { + break; + } + } + iter->entry = ht->table[iter->index]; } else { iter->entry = iter->nextEntry; } @@ -383,34 +474,45 @@ dictEntry *dictNext(dictIterator *iter) void dictReleaseIterator(dictIterator *iter) { + if (!(iter->index == -1 && iter->table == 0)) iter->d->iterators--; _dictFree(iter); } /* Return a random entry from the hash table. Useful to * implement randomized algorithms */ -dictEntry *dictGetRandomKey(dict *ht) +dictEntry *dictGetRandomKey(dict *d) { - dictEntry *he; + dictEntry *he, *orighe; unsigned int h; int listlen, listele; - if (ht->used == 0) return NULL; - do { - h = random() & ht->sizemask; - he = ht->table[h]; - } while(he == NULL); + if (dictSize(d) == 0) return NULL; + if (dictIsRehashing(d)) _dictRehashStep(d); + if (dictIsRehashing(d)) { + do { + h = random() % (d->ht[0].size+d->ht[1].size); + he = (h >= d->ht[0].size) ? d->ht[1].table[h - d->ht[0].size] : + d->ht[0].table[h]; + } while(he == NULL); + } else { + do { + h = random() & d->ht[0].sizemask; + he = d->ht[0].table[h]; + } while(he == NULL); + } /* Now we found a non empty bucket, but it is a linked * list and we need to get a random element from the list. - * The only sane way to do so is to count the element and + * The only sane way to do so is counting the elements and * select a random index. */ listlen = 0; + orighe = he; while(he) { he = he->next; listlen++; } listele = random() % listlen; - he = ht->table[h]; + he = orighe; while(listele--) he = he->next; return he; } @@ -418,14 +520,16 @@ dictEntry *dictGetRandomKey(dict *ht) /* ------------------------- private functions ------------------------------ */ /* Expand the hash table if needed */ -static int _dictExpandIfNeeded(dict *ht) +static int _dictExpandIfNeeded(dict *d) { /* If the hash table is empty expand it to the intial size, * if the table is "full" dobule its size. */ - if (ht->size == 0) - return dictExpand(ht, DICT_HT_INITIAL_SIZE); - if (ht->used >= ht->size && dict_can_resize) - return dictExpand(ht, ((ht->size > ht->used) ? ht->size : ht->used)*2); + if (dictIsRehashing(d)) return DICT_OK; + if (d->ht[0].size == 0) + return dictExpand(d, DICT_HT_INITIAL_SIZE); + if (d->ht[0].used >= d->ht[0].size && dict_can_resize) + return dictExpand(d, ((d->ht[0].size > d->ht[0].used) ? + d->ht[0].size : d->ht[0].used)*2); return DICT_OK; } @@ -444,33 +548,43 @@ static unsigned long _dictNextPower(unsigned long size) /* Returns the index of a free slot that can be populated with * an hash entry for the given 'key'. - * If the key already exists, -1 is returned. */ -static int _dictKeyIndex(dict *ht, const void *key) + * If the key already exists, -1 is returned. + * + * Note that if we are in the process of rehashing the hash table, the + * index is always returned in the context of the second (new) hash table. */ +static int _dictKeyIndex(dict *d, const void *key) { - unsigned int h; + unsigned int h, idx, table; dictEntry *he; /* Expand the hashtable if needed */ - if (_dictExpandIfNeeded(ht) == DICT_ERR) + if (_dictExpandIfNeeded(d) == DICT_ERR) return -1; /* Compute the key hash value */ - h = dictHashKey(ht, key) & ht->sizemask; - /* Search if this slot does not already contain the given key */ - he = ht->table[h]; - while(he) { - if (dictCompareHashKeys(ht, key, he->key)) - return -1; - he = he->next; + h = dictHashKey(d, key); + for (table = 0; table <= 1; table++) { + idx = h & d->ht[table].sizemask; + /* Search if this slot does not already contain the given key */ + he = d->ht[table].table[idx]; + while(he) { + if (dictCompareHashKeys(d, key, he->key)) + return -1; + he = he->next; + } + if (!dictIsRehashing(d)) break; } - return h; + return idx; } -void dictEmpty(dict *ht) { - _dictClear(ht); +void dictEmpty(dict *d) { + _dictClear(d,&d->ht[0]); + _dictClear(d,&d->ht[1]); + d->rehashidx = -1; + d->iterators = 0; } #define DICT_STATS_VECTLEN 50 -void dictPrintStats(dict *ht) { +static void _dictPrintStatsHt(dictht *ht) { unsigned long i, slots = 0, chainlen, maxchainlen = 0; unsigned long totchainlen = 0; unsigned long clvector[DICT_STATS_VECTLEN]; @@ -514,6 +628,14 @@ void dictPrintStats(dict *ht) { } } +void dictPrintStats(dict *d) { + _dictPrintStatsHt(&d->ht[0]); + if (dictIsRehashing(d)) { + printf("-- Rehashing into ht[1]:\n"); + _dictPrintStatsHt(&d->ht[1]); + } +} + void dictEnableResize(void) { dict_can_resize = 1; }