这里主要是generic分配，功能比较直白。
/* Defrag helper for generic allocations.
*
* returns NULL in case the allocation wasn't moved.
* when it returns a non-null value, the old pointer was already released
* and should NOT be accessed. */
void* activeDefragAlloc(void *ptr) {
size_t size;
void *newptr;
if(!je_get_defrag_hint(ptr)) {
server.stat_active_defrag_misses++;
return NULL;
}
/* move this allocation to a new allocation.
* make sure not to use the thread cache. so that we don't get back the same
* pointers we try to free */
size = zmalloc_size(ptr);
newptr = zmalloc_no_tcache(size);
memcpy(newptr, ptr, size);
zfree_no_tcache(ptr);
return newptr;
}
/*Defrag helper for sds strings
*
* returns NULL in case the allocation wasn't moved.
* when it returns a non-null value, the old pointer was already released
* and should NOT be accessed. */
sds activeDefragSds(sds sdsptr) {
void* ptr = sdsAllocPtr(sdsptr);
void* newptr = activeDefragAlloc(ptr);
if (newptr) {
size_t offset = sdsptr - (char*)ptr;
sdsptr = (char*)newptr + offset;
return sdsptr;
}
return NULL;
}
/* Defrag helper for robj and/or string objects
*
* returns NULL in case the allocation wasn't moved.
* when it returns a non-null value, the old pointer was already released
* and should NOT be accessed. */
robj *activeDefragStringOb(robj* ob, long *defragged) {
robj *ret = NULL;
if (ob->refcount!=1)
return NULL;
/* try to defrag robj (only if not an EMBSTR type (handled below). */
if (ob->type!=OBJ_STRING || ob->encoding!=OBJ_ENCODING_EMBSTR) {
if ((ret = activeDefragAlloc(ob))) {
ob = ret;
(*defragged)++;
}
}
/* try to defrag string object */
if (ob->type == OBJ_STRING) {
if(ob->encoding==OBJ_ENCODING_RAW) {
sds newsds = activeDefragSds((sds)ob->ptr);
if (newsds) {
ob->ptr = newsds;
(*defragged)++;
}
} else if (ob->encoding==OBJ_ENCODING_EMBSTR) {
/* The sds is embedded in the object allocation, calculate the
* offset and update the pointer in the new allocation. */
long ofs = (intptr_t)ob->ptr - (intptr_t)ob;
if ((ret = activeDefragAlloc(ob))) {
ret->ptr = (void*)((intptr_t)ret + ofs);
(*defragged)++;
}
} else if (ob->encoding!=OBJ_ENCODING_INT) {
serverPanic("Unknown string encoding");
}
}
return ret;
}
/* Defrag helper for dictEntries to be used during dict iteration (called on
* each step). Returns a stat of how many pointers were moved. */
long dictIterDefragEntry(dictIterator *iter) {
/* This function is a little bit dirty since it messes with the internals
* of the dict and it's iterator, but the benefit is that it is very easy
* to use, and require no other changes in the dict. */
long defragged = 0;
dictht *ht;
/* Handle the next entry (if there is one), and update the pointer in the
* current entry. */
if (iter->nextEntry) {
dictEntry *newde = activeDefragAlloc(iter->nextEntry);
if (newde) {
defragged++;
iter->nextEntry = newde;
iter->entry->next = newde;
}
}
/* handle the case of the first entry in the hash bucket. */
ht = &iter->d->ht[iter->table];
if (ht->table[iter->index] == iter->entry) {
dictEntry *newde = activeDefragAlloc(iter->entry);
if (newde) {
iter->entry = newde;
ht->table[iter->index] = newde;
defragged++;
}
}
return defragged;
}
/* Defrag helper for dict main allocations (dict struct, and hash tables).
* receives a pointer to the dict* and implicitly updates it when the dict
* struct itself was moved. Returns a stat of how many pointers were moved. */
long dictDefragTables(dict* d) {
dictEntry **newtable;
long defragged = 0;
/* handle the first hash table */
newtable = activeDefragAlloc(d->ht[0].table);
if (newtable)
defragged++, d->ht[0].table = newtable;
/* handle the second hash table */
if (d->ht[1].table) {
newtable = activeDefragAlloc(d->ht[1].table);
if (newtable)
defragged++, d->ht[1].table = newtable;
}
return defragged;
}
/* Internal function used by zslDefrag */
void zslUpdateNode(zskiplist *zsl, zskiplistNode *oldnode, zskiplistNode *newnode, zskiplistNode **update) {
int i;
for (i = 0; i < zsl->level; i++) {
if (update[i]->level[i].forward == oldnode)
update[i]->level[i].forward = newnode;
}
serverAssert(zsl->header!=oldnode);
if (newnode->level[0].forward) {
serverAssert(newnode->level[0].forward->backward==oldnode);
newnode->level[0].forward->backward = newnode;
} else {
serverAssert(zsl->tail==oldnode);
zsl->tail = newnode;
}
}
/* Defrag helper for sorted set.
* Update the robj pointer, defrag the skiplist struct and return the new score
* reference. We may not access oldele pointer (not even the pointer stored in
* the skiplist), as it was already freed. Newele may be null, in which case we
* only need to defrag the skiplist, but not update the obj pointer.
* When return value is non-NULL, it is the score reference that must be updated
* in the dict record. */
double *zslDefrag(zskiplist *zsl, double score, sds oldele, sds newele) {
zskiplistNode *update[ZSKIPLIST_MAXLEVEL], *x, *newx;
int i;
sds ele = newele? newele: oldele;
/* find the skiplist node referring to the object that was moved,
* and all pointers that need to be updated if we'll end up moving the skiplist node. */
x = zsl->header;
for (i = zsl->level-1; i >= 0; i--) {
while (x->level[i].forward &&
x->level[i].forward->ele != oldele && /* make sure not to access the
->obj pointer if it matches
oldele */
(x->level[i].forward->score < score ||
(x->level[i].forward->score == score &&
sdscmp(x->level[i].forward->ele,ele) < 0)))
x = x->level[i].forward;
update[i] = x;
}
/* update the robj pointer inside the skip list record. */
x = x->level[0].forward;
serverAssert(x && score == x->score && x->ele==oldele);
if (newele)
x->ele = newele;
/* try to defrag the skiplist record itself */
newx = activeDefragAlloc(x);
if (newx) {
zslUpdateNode(zsl, x, newx, update);
return &newx->score;
}
return NULL;
}
/* Defrag helper for sorted set.
* Defrag a single dict entry key name, and corresponding skiplist struct */
long activeDefragZsetEntry(zset *zs, dictEntry *de) {
sds newsds;
double* newscore;
long defragged = 0;
sds sdsele = dictGetKey(de);
if ((newsds = activeDefragSds(sdsele)))
defragged++, de->key = newsds;
newscore = zslDefrag(zs->zsl, *(double*)dictGetVal(de), sdsele, newsds);
if (newscore) {
dictSetVal(zs->dict, de, newscore);
defragged++;
}
return defragged;
}
#define DEFRAG_SDS_DICT_NO_VAL 0
#define DEFRAG_SDS_DICT_VAL_IS_SDS 1
#define DEFRAG_SDS_DICT_VAL_IS_STROB 2
#define DEFRAG_SDS_DICT_VAL_VOID_PTR 3
/* Defrag a dict with sds key and optional value (either ptr, sds or robj string) */
long activeDefragSdsDict(dict* d, int val_type) {
dictIterator *di;
dictEntry *de;
long defragged = 0;
di = dictGetIterator(d);
while((de = dictNext(di)) != NULL) {
sds sdsele = dictGetKey(de), newsds;
if ((newsds = activeDefragSds(sdsele)))
de->key = newsds, defragged++;
/* defrag the value */
if (val_type == DEFRAG_SDS_DICT_VAL_IS_SDS) {
sdsele = dictGetVal(de);
if ((newsds = activeDefragSds(sdsele)))
de->v.val = newsds, defragged++;
} else if (val_type == DEFRAG_SDS_DICT_VAL_IS_STROB) {
robj *newele, *ele = dictGetVal(de);
if ((newele = activeDefragStringOb(ele, &defragged)))
de->v.val = newele;
} else if (val_type == DEFRAG_SDS_DICT_VAL_VOID_PTR) {
void *newptr, *ptr = dictGetVal(de);
if ((newptr = activeDefragAlloc(ptr)))
de->v.val = newptr, defragged++;
}
defragged += dictIterDefragEntry(di);
}
dictReleaseIterator(di);
return defragged;
}
/* Defrag a list of ptr, sds or robj string values */
long activeDefragList(list *l, int val_type) {
long defragged = 0;
listNode *ln, *newln;
for (ln = l->head; ln; ln = ln->next) {
if ((newln = activeDefragAlloc(ln))) {
if (newln->prev)
newln->prev->next = newln;
else
l->head = newln;
if (newln->next)
newln->next->prev = newln;
else
l->tail = newln;
ln = newln;
defragged++;
}
if (val_type == DEFRAG_SDS_DICT_VAL_IS_SDS) {
sds newsds, sdsele = ln->value;
if ((newsds = activeDefragSds(sdsele)))
ln->value = newsds, defragged++;
} else if (val_type == DEFRAG_SDS_DICT_VAL_IS_STROB) {
robj *newele, *ele = ln->value;
if ((newele = activeDefragStringOb(ele, &defragged)))
ln->value = newele;
} else if (val_type == DEFRAG_SDS_DICT_VAL_VOID_PTR) {
void *newptr, *ptr = ln->value;
if ((newptr = activeDefragAlloc(ptr)))
ln->value = newptr, defragged++;
}
}
return defragged;
}