/*
* Active memory defragmentation
* Try to find key / value allocations that need to be re-allocated in order
* to reduce external fragmentation.
* We do that by scanning the keyspace and for each pointer we have, we can try to
* ask the allocator if moving it to a new address will help reduce fragmentation.
*
* Copyright (c) 2017, Oran Agra
* Copyright (c) 2017, Redis Labs, Inc
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of Redis nor the names of its contributors may be used
* to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include "server.h"
#include <time.h>
#include <assert.h>
#include <stddef.h>
#ifdef HAVE_DEFRAG
/* this method was added to jemalloc in order to help us understand which
* pointers are worthwhile moving and which aren't */
int je_get_defrag_hint(void* ptr, int *bin_util, int *run_util);
/* forward declarations*/
void defragDictBucketCallback(void *privdata, dictEntry **bucketref);
dictEntry* replaceSateliteDictKeyPtrAndOrDefragDictEntry(dict *d, sds oldkey, sds newkey, unsigned int hash, long *defragged);
/* Defrag helper for generic allocations.
*
* returns NULL in case the allocatoin 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) {
int bin_util, run_util;
size_t size;
void *newptr;
if(!je_get_defrag_hint(ptr, &bin_util, &run_util)) {
server.stat_active_defrag_misses++;
return NULL;
}
/* if this run is more utilized than the average utilization in this bin
* (or it is full), skip it. This will eventually move all the allocations
* from relatively empty runs into relatively full runs. */
if (run_util > bin_util || run_util == 1<<16) {
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 allocatoin 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 allocatoin 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). Teturns 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 chagnes 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 helpler 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;
}
/* Defrag a list of sds values and a dict with the same sds keys */
long activeDefragSdsListAndDict(list *l, dict *d, int dict_val_type) {
long defragged = 0;
sds newsds, sdsele;
listNode *ln, *newln;
dictIterator *di;
dictEntry *de;
/* Defrag the list and it's sds values */
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++;
}
sdsele = ln->value;
if ((newsds = activeDefragSds(sdsele))) {
/* When defragging an sds value, we need to update the dict key */
unsigned int hash = dictGetHash(d, sdsele);
replaceSateliteDictKeyPtrAndOrDefragDictEntry(d, sdsele, newsds, hash, &defragged);
ln->value = newsds;
defragged++;
}
}
/* Defrag the dict values (keys were already handled) */
di = dictGetIterator(d);
while((de = dictNext(di)) != NULL) {
if (dict_val_type == DEFRAG_SDS_DICT_VAL_IS_SDS) {
sds newsds, sdsele = dictGetVal(de);
if ((newsds = activeDefragSds(sdsele)))
de->v.val = newsds, defragged++;
} else if (dict_val_type == DEFRAG_SDS_DICT_VAL_IS_STROB) {
robj *newele, *ele = dictGetVal(de);
if ((newele = activeDefragStringOb(ele, &defragged)))
de->v.val = newele, defragged++;
} else if (dict_val_type == DEFRAG_SDS_DICT_VAL_VOID_PTR) {
void *newptr, *ptr = ln->value;
if ((newptr = activeDefragAlloc(ptr)))
ln->value = newptr, defragged++;
}
defragged += dictIterDefragEntry(di);
}
dictReleaseIterator(di);
return defragged;
}
/* Utility function that replaces an old key pointer in the dictionary with a
* new pointer. Additionally, we try to defrag the dictEntry in that dict.
* Oldkey mey be a dead pointer and should not be accessed (we get a
* pre-calculated hash value). Newkey may be null if the key pointer wasn't
* moved. Return value is the the dictEntry if found, or NULL if not found.
* NOTE: this is very ugly code, but it let's us avoid the complication of
* doing a scan on another dict. */
dictEntry* replaceSateliteDictKeyPtrAndOrDefragDictEntry(dict *d, sds oldkey, sds newkey, unsigned int hash, long *defragged) {
dictEntry **deref = dictFindEntryRefByPtrAndHash(d, oldkey, hash);
if (deref) {
dictEntry *de = *deref;
dictEntry *newde = activeDefragAlloc(de);
if (newde) {
de = *deref = newde;
(*defragged)++;
}
if (newkey)
de->key = newkey;
return de;
}
return NULL;
}
long activeDefragQuickListNodes(quicklist *ql) {
quicklistNode *node = ql->head, *newnode;
long defragged = 0;
unsigned char *newzl;
while (node) {
if ((newnode = activeDefragAlloc(node))) {
if (newnode->prev)
newnode->prev->next = newnode;
else
ql->head = newnode;
if (newnode->next)
newnode->next->prev = newnode;
else
ql->tail = newnode;
node = newnode;
defragged++;
}
if ((newzl = activeDefragAlloc(node->zl)))
defragged++, node->zl = newzl;
node = node->next;
}
return defragged;
}
/* when the value has lots of elements, we want to handle it later and not as
* oart of the main dictionary scan. this is needed in order to prevent latency
* spikes when handling large items */
void defragLater(redisDb *db, dictEntry *kde) {
sds key = sdsdup(dictGetKey(kde));
listAddNodeTail(db->defrag_later, key);
}
long scanLaterList(robj *ob) {
quicklist *ql = ob->ptr;
if (ob->type != OBJ_LIST || ob->encoding != OBJ_ENCODING_QUICKLIST)
return 0;
server.stat_active_defrag_scanned+=ql->len;
return activeDefragQuickListNodes(ql);
}
typedef struct {
zset *zs;
long defragged;
} scanLaterZsetData;
void scanLaterZsetCallback(void *privdata, const dictEntry *_de) {
dictEntry *de = (dictEntry*)_de;
scanLaterZsetData *data = privdata;
data->defragged += activeDefragZsetEntry(data->zs, de);
server.stat_active_defrag_scanned++;
}
long scanLaterZset(robj *ob, unsigned long *cursor) {
if (ob->type != OBJ_ZSET || ob->encoding != OBJ_ENCODING_SKIPLIST)
return 0;
zset *zs = (zset*)ob->ptr;
dict *d = zs->dict;
scanLaterZsetData data = {zs, 0};
*cursor = dictScan(d, *cursor, scanLaterZsetCallback, defragDictBucketCallback, &data);
return data.defragged;
}
void scanLaterSetCallback(void *privdata, const dictEntry *_de) {
dictEntry *de = (dictEntry*)_de;
long *defragged = privdata;
sds sdsele = dictGetKey(de), newsds;
if ((newsds = activeDefragSds(sdsele)))
(*defragged)++, de->key = newsds;
server.stat_active_defrag_scanned++;
}
long scanLaterSet(robj *ob, unsigned long *cursor) {
long defragged = 0;
if (ob->type != OBJ_SET || ob->encoding != OBJ_ENCODING_HT)
return 0;
dict *d = ob->ptr;
*cursor = dictScan(d, *cursor, scanLaterSetCallback, defragDictBucketCallback, &defragged);
return defragged;
}
void scanLaterHashCallback(void *privdata, const dictEntry *_de) {
dictEntry *de = (dictEntry*)_de;
long *defragged = privdata;
sds sdsele = dictGetKey(de), newsds;
if ((newsds = activeDefragSds(sdsele)))
(*defragged)++, de->key = newsds;
sdsele = dictGetVal(de);
if ((newsds = activeDefragSds(sdsele)))
(*defragged)++, de->v.val = newsds;
server.stat_active_defrag_scanned++;
}
long scanLaterHash(robj *ob, unsigned long *cursor) {
long defragged = 0;
if (ob->type != OBJ_HASH || ob->encoding != OBJ_ENCODING_HT)
return 0;
dict *d = ob->ptr;
*cursor = dictScan(d, *cursor, scanLaterHashCallback, defragDictBucketCallback, &defragged);
return defragged;
}
long defragQuicklist(redisDb *db, dictEntry *kde) {
robj *ob = dictGetVal(kde);
long defragged = 0;
quicklist *ql = ob->ptr, *newql;
serverAssert(ob->type == OBJ_LIST && ob->encoding == OBJ_ENCODING_QUICKLIST);
if ((newql = activeDefragAlloc(ql)))
defragged++, ob->ptr = ql = newql;
if (ql->len > server.active_defrag_max_scan_fields)
defragLater(db, kde);
else
defragged += activeDefragQuickListNodes(ql);
return defragged;
}
long defragZsetSkiplist(redisDb *db, dictEntry *kde) {
robj *ob = dictGetVal(kde);
long defragged = 0;
zset *zs = (zset*)ob->ptr;
zset *newzs;
zskiplist *newzsl;
dict *newdict;
dictEntry *de;
struct zskiplistNode *newheader;
serverAssert(ob->type == OBJ_ZSET && ob->encoding == OBJ_ENCODING_SKIPLIST);
if ((newzs = activeDefragAlloc(zs)))
defragged++, ob->ptr = zs = newzs;
if ((newzsl = activeDefragAlloc(zs->zsl)))
defragged++, zs->zsl = newzsl;
if ((newheader = activeDefragAlloc(zs->zsl->header)))
defragged++, zs->zsl->header = newheader;
if (dictSize(zs->dict) > server.active_defrag_max_scan_fields)
defragLater(db, kde);
else {
dictIterator *di = dictGetIterator(zs->dict);
while((de = dictNext(di)) != NULL) {
defragged += activeDefragZsetEntry(zs, de);
}
dictReleaseIterator(di);
}
/* handle the dict struct */
if ((newdict = activeDefragAlloc(zs->dict)))
defragged++, zs->dict = newdict;
/* defrag the dict tables */
defragged += dictDefragTables(zs->dict);
return defragged;
}
long defragHash(redisDb *db, dictEntry *kde) {
long defragged = 0;
robj *ob = dictGetVal(kde);
dict *d, *newd;
serverAssert(ob->type == OBJ_HASH && ob->encoding == OBJ_ENCODING_HT);
d = ob->ptr;
if (dictSize(d) > server.active_defrag_max_scan_fields)
defragLater(db, kde);
else
defragged += activeDefragSdsDict(d, DEFRAG_SDS_DICT_VAL_IS_SDS);
/* handle the dict struct */
if ((newd = activeDefragAlloc(ob->ptr)))
defragged++, ob->ptr = newd;
/* defrag the dict tables */
defragged += dictDefragTables(ob->ptr);
return defragged;
}
long defragSet(redisDb *db, dictEntry *kde) {
long defragged = 0;
robj *ob = dictGetVal(kde);
dict *d, *newd;
serverAssert(ob->type == OBJ_SET && ob->encoding == OBJ_ENCODING_HT);
d = ob->ptr;
if (dictSize(d) > server.active_defrag_max_scan_fields)
defragLater(db, kde);
else
defragged += activeDefragSdsDict(d, DEFRAG_SDS_DICT_NO_VAL);
/* handle the dict struct */
if ((newd = activeDefragAlloc(ob->ptr)))
defragged++, ob->ptr = newd;
/* defrag the dict tables */
defragged += dictDefragTables(ob->ptr);
return defragged;
}
/* for each key we scan in the main dict, this function will attempt to defrag
* all the various pointers it has. Returns a stat of how many pointers were
* moved. */
long defragKey(redisDb *db, dictEntry *de) {
sds keysds = dictGetKey(de);
robj *newob, *ob;
unsigned char *newzl;
long defragged = 0;
sds newsds;
/* Try to defrag the key name. */
newsds = activeDefragSds(keysds);
if (newsds)
defragged++, de->key = newsds;
if (dictSize(db->expires)) {
/* Dirty code:
* I can't search in db->expires for that key after i already released
* the pointer it holds it won't be able to do the string compare */
uint64_t hash = dictGetHash(db->dict, de->key);
replaceSateliteDictKeyPtrAndOrDefragDictEntry(db->expires, keysds, newsds, hash, &defragged);
}
/* Try to defrag robj and / or string value. */
ob = dictGetVal(de);
if ((newob = activeDefragStringOb(ob, &defragged))) {
de->v.val = newob;
ob = newob;
}
if (ob->type == OBJ_STRING) {
/* Already handled in activeDefragStringOb. */
} else if (ob->type == OBJ_LIST) {
if (ob->encoding == OBJ_ENCODING_QUICKLIST) {
defragged += defragQuicklist(db, de);
} else if (ob->encoding == OBJ_ENCODING_ZIPLIST) {
if ((newzl = activeDefragAlloc(ob->ptr)))
defragged++, ob->ptr = newzl;
} else {
serverPanic("Unknown list encoding");
}
} else if (ob->type == OBJ_SET) {
if (ob->encoding == OBJ_ENCODING_HT) {
defragged += defragSet(db, de);
} else if (ob->encoding == OBJ_ENCODING_INTSET) {
intset *newis, *is = ob->ptr;
if ((newis = activeDefragAlloc(is)))
defragged++, ob->ptr = newis;
} else {
serverPanic("Unknown set encoding");
}
} else if (ob->type == OBJ_ZSET) {
if (ob->encoding == OBJ_ENCODING_ZIPLIST) {
if ((newzl = activeDefragAlloc(ob->ptr)))
defragged++, ob->ptr = newzl;
} else if (ob->encoding == OBJ_ENCODING_SKIPLIST) {
defragged += defragZsetSkiplist(db, de);
} else {
serverPanic("Unknown sorted set encoding");
}
} else if (ob->type == OBJ_HASH) {
if (ob->encoding == OBJ_ENCODING_ZIPLIST) {
if ((newzl = activeDefragAlloc(ob->ptr)))
defragged++, ob->ptr = newzl;
} else if (ob->encoding == OBJ_ENCODING_HT) {
defragged += defragHash(db, de);
} else {
serverPanic("Unknown hash encoding");
}
} else if (ob->type == OBJ_MODULE) {
/* Currently defragmenting modules private data types
* is not supported. */
} else {
serverPanic("Unknown object type");
}
return defragged;
}
/* Defrag scan callback for the main db dictionary. */
void defragScanCallback(void *privdata, const dictEntry *de) {
long defragged = defragKey((redisDb*)privdata, (dictEntry*)de);
server.stat_active_defrag_hits += defragged;
if(defragged)
server.stat_active_defrag_key_hits++;
else
server.stat_active_defrag_key_misses++;
server.stat_active_defrag_scanned++;
}
/* Defrag scan callback for for each hash table bicket,
* used in order to defrag the dictEntry allocations. */
void defragDictBucketCallback(void *privdata, dictEntry **bucketref) {
UNUSED(privdata); /* NOTE: this function is also used by both activeDefragCycle and scanLaterHash, etc. don't use privdata */
while(*bucketref) {
dictEntry *de = *bucketref, *newde;
if ((newde = activeDefragAlloc(de))) {
*bucketref = newde;
}
bucketref = &(*bucketref)->next;
}
}
/* Utility function to get the fragmentation ratio from jemalloc.
* It is critical to do that by comparing only heap maps that belong to
* jemalloc, and skip ones the jemalloc keeps as spare. Since we use this
* fragmentation ratio in order to decide if a defrag action should be taken
* or not, a false detection can cause the defragmenter to waste a lot of CPU
* without the possibility of getting any results. */
float getAllocatorFragmentation(size_t *out_frag_bytes) {
size_t epoch = 1, allocated = 0, resident = 0, active = 0, sz = sizeof(size_t);
/* Update the statistics cached by mallctl. */
je_mallctl("epoch", &epoch, &sz, &epoch, sz);
/* Unlike RSS, this does not include RSS from shared libraries and other non
* heap mappings. */
je_mallctl("stats.resident", &resident, &sz, NULL, 0);
/* Unlike resident, this doesn't not include the pages jemalloc reserves
* for re-use (purge will clean that). */
je_mallctl("stats.active", &active, &sz, NULL, 0);
/* Unlike zmalloc_used_memory, this matches the stats.resident by taking
* into account all allocations done by this process (not only zmalloc). */
je_mallctl("stats.allocated", &allocated, &sz, NULL, 0);
float frag_pct = ((float)active / allocated)*100 - 100;
size_t frag_bytes = active - allocated;
float rss_pct = ((float)resident / allocated)*100 - 100;
size_t rss_bytes = resident - allocated;
if(out_frag_bytes)
*out_frag_bytes = frag_bytes;
serverLog(LL_DEBUG,
"allocated=%zu, active=%zu, resident=%zu, frag=%.0f%% (%.0f%% rss), frag_bytes=%zu (%zu rss)",
allocated, active, resident, frag_pct, rss_pct, frag_bytes, rss_bytes);
return frag_pct;
}
/* We may need to defrag other globals, one small allcation can hold a full allocator run.
* so although small, it is still important to defrag these */
long defragOtherGlobals() {
long defragged = 0;
/* there are many more pointers to defrag (e.g. client argv, output / aof buffers, etc.
* but we assume most of these are short lived, we only need to defrag allocations
* that remain static for a long time */
defragged += activeDefragSdsDict(server.lua_scripts, DEFRAG_SDS_DICT_VAL_IS_STROB);
defragged += activeDefragSdsListAndDict(server.repl_scriptcache_fifo, server.repl_scriptcache_dict, DEFRAG_SDS_DICT_NO_VAL);
return defragged;
}
unsigned long defragLaterItem(dictEntry *de, unsigned long cursor) {
long defragged = 0;
if (de) {
robj *ob = dictGetVal(de);
if (ob->type == OBJ_LIST) {
defragged += scanLaterList(ob);
cursor = 0; /* list has no scan, we must finish it in one go */
} else if (ob->type == OBJ_SET) {
defragged += scanLaterSet(ob, &cursor);
} else if (ob->type == OBJ_ZSET) {
defragged += scanLaterZset(ob, &cursor);
} else if (ob->type == OBJ_HASH) {
defragged += scanLaterHash(ob, &cursor);
} else {
cursor = 0; /* object type may have changed since we schedule it for later */
}
} else {
cursor = 0; /* object may have been deleted already */
}
server.stat_active_defrag_hits += defragged;
return cursor;
}
/* returns 0 if no more work needs to be been done, and 1 if time is up and more work is needed. */
int defragLaterStep(redisDb *db, long long endtime) {
static sds current_key = NULL;
static unsigned long cursor = 0;
unsigned int iterations = 0;
unsigned long long prev_defragged = server.stat_active_defrag_hits;
unsigned long long prev_scanned = server.stat_active_defrag_scanned;
long long key_defragged;
do {
/* if we're not continuing a scan from the last call or loop, start a new one */
if (!cursor) {
listNode *head = listFirst(db->defrag_later);
/* Move on to next key */
if (current_key) {
serverAssert(current_key == head->value);
sdsfree(head->value);
listDelNode(db->defrag_later, head);
cursor = 0;
current_key = NULL;
}
/* stop if we reached the last one. */
head = listFirst(db->defrag_later);
if (!head)
return 0;
/* start a new key */
current_key = head->value;
cursor = 0;
}
/* each time we enter this function we need to fetch the key from the dict again (if it still exists) */
dictEntry *de = dictFind(db->dict, current_key);
key_defragged = server.stat_active_defrag_hits;
do {
cursor = defragLaterItem(de, cursor);
/* Once in 16 scan iterations, 512 pointer reallocations, or 64 fields
* (if we have a lot of pointers in one hash bucket, or rehashing),
* check if we reached the time limit.
* But regardless, don't start a new BIG key in this loop, this is because the
* next key can be a list, and scanLaterList must be done in once cycle */
if (!cursor || (++iterations > 16 ||
server.stat_active_defrag_hits - prev_defragged > 512 ||
server.stat_active_defrag_scanned - prev_scanned > 64)) {
if (!cursor || ustime() > endtime) {
if(key_defragged != server.stat_active_defrag_hits)
server.stat_active_defrag_key_hits++;
else
server.stat_active_defrag_key_misses++;
return 1;
}
iterations = 0;
prev_defragged = server.stat_active_defrag_hits;
prev_scanned = server.stat_active_defrag_scanned;
}
} while(cursor);
if(key_defragged != server.stat_active_defrag_hits)
server.stat_active_defrag_key_hits++;
else
server.stat_active_defrag_key_misses++;
} while(1);
}
#define INTERPOLATE(x, x1, x2, y1, y2) ( (y1) + ((x)-(x1)) * ((y2)-(y1)) / ((x2)-(x1)) )
#define LIMIT(y, min, max) ((y)<(min)? min: ((y)>(max)? max: (y)))
/* decide if defrag is needed, and at what CPU effort to invest in it */
void computeDefragCycles() {
size_t frag_bytes;
float frag_pct = getAllocatorFragmentation(&frag_bytes);
/* If we're not already running, and below the threshold, exit. */
if (!server.active_defrag_running) {
if(frag_pct < server.active_defrag_threshold_lower || frag_bytes < server.active_defrag_ignore_bytes)
return;
}
/* Calculate the adaptive aggressiveness of the defrag */
int cpu_pct = INTERPOLATE(frag_pct,
server.active_defrag_threshold_lower,
server.active_defrag_threshold_upper,
server.active_defrag_cycle_min,
server.active_defrag_cycle_max);
cpu_pct = LIMIT(cpu_pct,
server.active_defrag_cycle_min,
server.active_defrag_cycle_max);
/* We allow increasing the aggressiveness during a scan, but don't
* reduce it. */
if (!server.active_defrag_running ||
cpu_pct > server.active_defrag_running)
{
server.active_defrag_running = cpu_pct;
serverLog(LL_VERBOSE,
"Starting active defrag, frag=%.0f%%, frag_bytes=%zu, cpu=%d%%",
frag_pct, frag_bytes, cpu_pct);
}
}
/* Perform incremental defragmentation work from the serverCron.
* This works in a similar way to activeExpireCycle, in the sense that
* we do incremental work across calls. */
void activeDefragCycle(void) {
static int current_db = -1;
static unsigned long cursor = 0;
static redisDb *db = NULL;
static long long start_scan, start_stat;
unsigned int iterations = 0;
unsigned long long prev_defragged = server.stat_active_defrag_hits;
unsigned long long prev_scanned = server.stat_active_defrag_scanned;
long long start, timelimit, endtime;
mstime_t latency;
int quit = 0;
if (server.aof_child_pid!=-1 || server.rdb_child_pid!=-1)
return; /* Defragging memory while there's a fork will just do damage. */
/* Once a second, check if we the fragmentation justfies starting a scan
* or making it more aggressive. */
run_with_period(1000) {
computeDefragCycles();
}
if (!server.active_defrag_running)
return;
/* See activeExpireCycle for how timelimit is handled. */
start = ustime();
timelimit = 1000000*server.active_defrag_running/server.hz/100;
if (timelimit <= 0) timelimit = 1;
endtime = start + timelimit;
latencyStartMonitor(latency);
do {
/* if we're not continuing a scan from the last call or loop, start a new one */
if (!cursor) {
/* finish any leftovers from previous db before moving to the next one */
if (db && defragLaterStep(db, endtime)) {
quit = 1; /* time is up, we didn't finish all the work */
break; /* this will exit the function and we'll continue on the next cycle */
}
/* Move on to next database, and stop if we reached the last one. */
if (++current_db >= server.dbnum) {
/* defrag other items not part of the db / keys */
defragOtherGlobals();
long long now = ustime();
size_t frag_bytes;
float frag_pct = getAllocatorFragmentation(&frag_bytes);
serverLog(LL_VERBOSE,
"Active defrag done in %dms, reallocated=%d, frag=%.0f%%, frag_bytes=%zu",
(int)((now - start_scan)/1000), (int)(server.stat_active_defrag_hits - start_stat), frag_pct, frag_bytes);
start_scan = now;
current_db = -1;
cursor = 0;
db = NULL;
server.active_defrag_running = 0;
computeDefragCycles(); /* if another scan is needed, start it right away */
if (server.active_defrag_running != 0 && ustime() < endtime)
continue;
break;
}
else if (current_db==0) {
/* Start a scan from the first database. */
start_scan = ustime();
start_stat = server.stat_active_defrag_hits;
}
db = &server.db[current_db];
cursor = 0;
}
do {
/* before scanning the next bucket, see if we have big keys left from the previous bucket to scan */
if (defragLaterStep(db, endtime)) {
quit = 1; /* time is up, we didn't finish all the work */
break; /* this will exit the function and we'll continue on the next cycle */
}
cursor = dictScan(db->dict, cursor, defragScanCallback, defragDictBucketCallback, db);
/* Once in 16 scan iterations, 512 pointer reallocations. or 64 keys
* (if we have a lot of pointers in one hash bucket or rehasing),
* check if we reached the time limit.
* But regardless, don't start a new db in this loop, this is because after
* the last db we call defragOtherGlobals, which must be done in once cycle */
if (!cursor || (++iterations > 16 ||
server.stat_active_defrag_hits - prev_defragged > 512 ||
server.stat_active_defrag_scanned - prev_scanned > 64)) {
if (!cursor || ustime() > endtime) {
quit = 1;
break;
}
iterations = 0;
prev_defragged = server.stat_active_defrag_hits;
prev_scanned = server.stat_active_defrag_scanned;
}
} while(cursor && !quit);
} while(!quit);
latencyEndMonitor(latency);
latencyAddSampleIfNeeded("active-defrag-cycle",latency);
}
#else /* HAVE_DEFRAG */
void activeDefragCycle(void) {
/* Not implemented yet. */
}
#endif