githubmirror/redis

src/object.c
1 688 строк64 KB
judeng
use embedded string object and more efficient ll2string for long long value convert to string (#12250)
20 июн 2023, 15:14
20 июн 2023, 15:1493708c7
/* Redis Object implementation.
 *
 * Copyright (c) 2009-2012, Salvatore Sanfilippo <antirez at gmail dot com>
 * 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 "functions.h"
#include "intset.h"  /* Compact integer set structure */
#include <math.h>
#include <ctype.h>

#ifdef __CYGWIN__
#define strtold(a,b) ((long double)strtod((a),(b)))
#endif

/* ===================== Creation and parsing of objects ==================== */

robj *createObject(int type, void *ptr) {
    robj *o = zmalloc(sizeof(*o));
    o->type = type;
    o->encoding = OBJ_ENCODING_RAW;
    o->ptr = ptr;
    o->refcount = 1;
    o->lru = 0;
    return o;
}

void initObjectLRUOrLFU(robj *o) {
    if (o->refcount == OBJ_SHARED_REFCOUNT)
        return;
    /* Set the LRU to the current lruclock (minutes resolution), or
     * alternatively the LFU counter. */
    if (server.maxmemory_policy & MAXMEMORY_FLAG_LFU) {
        o->lru = (LFUGetTimeInMinutes() << 8) | LFU_INIT_VAL;
    } else {
        o->lru = LRU_CLOCK();
    }
    return;
}

/* Set a special refcount in the object to make it "shared":
 * incrRefCount and decrRefCount() will test for this special refcount
 * and will not touch the object. This way it is free to access shared
 * objects such as small integers from different threads without any
 * mutex.
 *
 * A common pattern to create shared objects:
 *
 * robj *myobject = makeObjectShared(createObject(...));
 *
 */
robj *makeObjectShared(robj *o) {
    serverAssert(o->refcount == 1);
    o->refcount = OBJ_SHARED_REFCOUNT;
    return o;
}

/* Create a string object with encoding OBJ_ENCODING_RAW, that is a plain
 * string object where o->ptr points to a proper sds string. */
robj *createRawStringObject(const char *ptr, size_t len) {
    return createObject(OBJ_STRING, sdsnewlen(ptr,len));
}

/* Create a string object with encoding OBJ_ENCODING_EMBSTR, that is
 * an object where the sds string is actually an unmodifiable string
 * allocated in the same chunk as the object itself. */
robj *createEmbeddedStringObject(const char *ptr, size_t len) {
    robj *o = zmalloc(sizeof(robj)+sizeof(struct sdshdr8)+len+1);
    struct sdshdr8 *sh = (void*)(o+1);

    o->type = OBJ_STRING;
    o->encoding = OBJ_ENCODING_EMBSTR;
    o->ptr = sh+1;
    o->refcount = 1;
    o->lru = 0;

    sh->len = len;
    sh->alloc = len;
    sh->flags = SDS_TYPE_8;
    if (ptr == SDS_NOINIT)
        sh->buf[len] = '\0';
    else if (ptr) {
        memcpy(sh->buf,ptr,len);
        sh->buf[len] = '\0';
    } else {
        memset(sh->buf,0,len+1);
    }
    return o;
}

/* Create a string object with EMBSTR encoding if it is smaller than
 * OBJ_ENCODING_EMBSTR_SIZE_LIMIT, otherwise the RAW encoding is
 * used.
 *
 * The current limit of 44 is chosen so that the biggest string object
 * we allocate as EMBSTR will still fit into the 64 byte arena of jemalloc. */
#define OBJ_ENCODING_EMBSTR_SIZE_LIMIT 44
robj *createStringObject(const char *ptr, size_t len) {
    if (len <= OBJ_ENCODING_EMBSTR_SIZE_LIMIT)
        return createEmbeddedStringObject(ptr,len);
    else
        return createRawStringObject(ptr,len);
}

/* Same as CreateRawStringObject, can return NULL if allocation fails */
robj *tryCreateRawStringObject(const char *ptr, size_t len) {
    sds str = sdstrynewlen(ptr,len);
    if (!str) return NULL;
    return createObject(OBJ_STRING, str);
}

/* Same as createStringObject, can return NULL if allocation fails */
robj *tryCreateStringObject(const char *ptr, size_t len) {
    if (len <= OBJ_ENCODING_EMBSTR_SIZE_LIMIT)
        return createEmbeddedStringObject(ptr,len);
    else
        return tryCreateRawStringObject(ptr,len);
}

/* Create a string object from a long long value according to the specified flag. */
#define LL2STROBJ_AUTO 0       /* automatically create the optimal string object */
#define LL2STROBJ_NO_SHARED 1  /* disallow shared objects */
#define LL2STROBJ_NO_INT_ENC 2 /* disallow integer encoded objects. */
robj *createStringObjectFromLongLongWithOptions(long long value, int flag) {
    robj *o;

    if (value >= 0 && value < OBJ_SHARED_INTEGERS && flag == LL2STROBJ_AUTO) {
        o = shared.integers[value];
    } else {
        if ((value >= LONG_MIN && value <= LONG_MAX) && flag != LL2STROBJ_NO_INT_ENC) {
            o = createObject(OBJ_STRING, NULL);
            o->encoding = OBJ_ENCODING_INT;
            o->ptr = (void*)((long)value);
        } else {
            char buf[LONG_STR_SIZE];
            int len = ll2string(buf, sizeof(buf), value);
            o = createStringObject(buf, len);
        }
    }
    return o;
}

/* Wrapper for createStringObjectFromLongLongWithOptions() always demanding
 * to create a shared object if possible. */
robj *createStringObjectFromLongLong(long long value) {
    return createStringObjectFromLongLongWithOptions(value, LL2STROBJ_AUTO);
}

/* The function avoids returning a shared integer when LFU/LRU info
 * are needed, that is, when the object is used as a value in the key
 * space(for instance when the INCR command is used), and Redis is
 * configured to evict based on LFU/LRU, so we want LFU/LRU values
 * specific for each key. */
robj *createStringObjectFromLongLongForValue(long long value) {
    if (server.maxmemory == 0 || !(server.maxmemory_policy & MAXMEMORY_FLAG_NO_SHARED_INTEGERS)) {
        /* If the maxmemory policy permits, we can still return shared integers */
        return createStringObjectFromLongLongWithOptions(value, LL2STROBJ_AUTO);
    } else {
        return createStringObjectFromLongLongWithOptions(value, LL2STROBJ_NO_SHARED);
    }
}

/* Create a string object that contains an sds inside it. That means it can't be
 * integer encoded (OBJ_ENCODING_INT), and it'll always be an EMBSTR type. */
robj *createStringObjectFromLongLongWithSds(long long value) {
    return createStringObjectFromLongLongWithOptions(value, LL2STROBJ_NO_INT_ENC);
}

/* Create a string object from a long double. If humanfriendly is non-zero
 * it does not use exponential format and trims trailing zeroes at the end,
 * however this results in loss of precision. Otherwise exp format is used
 * and the output of snprintf() is not modified.
 *
 * The 'humanfriendly' option is used for INCRBYFLOAT and HINCRBYFLOAT. */
robj *createStringObjectFromLongDouble(long double value, int humanfriendly) {
    char buf[MAX_LONG_DOUBLE_CHARS];
    int len = ld2string(buf,sizeof(buf),value,humanfriendly? LD_STR_HUMAN: LD_STR_AUTO);
    return createStringObject(buf,len);
}

/* Duplicate a string object, with the guarantee that the returned object
 * has the same encoding as the original one.
 *
 * This function also guarantees that duplicating a small integer object
 * (or a string object that contains a representation of a small integer)
 * will always result in a fresh object that is unshared (refcount == 1).
 *
 * The resulting object always has refcount set to 1. */
robj *dupStringObject(const robj *o) {
    robj *d;

    serverAssert(o->type == OBJ_STRING);

    switch(o->encoding) {
    case OBJ_ENCODING_RAW:
        return createRawStringObject(o->ptr,sdslen(o->ptr));
    case OBJ_ENCODING_EMBSTR:
        return createEmbeddedStringObject(o->ptr,sdslen(o->ptr));
    case OBJ_ENCODING_INT:
        d = createObject(OBJ_STRING, NULL);
        d->encoding = OBJ_ENCODING_INT;
        d->ptr = o->ptr;
        return d;
    default:
        serverPanic("Wrong encoding.");
        break;
    }
}

robj *createQuicklistObject(void) {
    quicklist *l = quicklistCreate();
    robj *o = createObject(OBJ_LIST,l);
    o->encoding = OBJ_ENCODING_QUICKLIST;
    return o;
}

robj *createListListpackObject(void) {
    unsigned char *lp = lpNew(0);
    robj *o = createObject(OBJ_LIST,lp);
    o->encoding = OBJ_ENCODING_LISTPACK;
    return o;
}

robj *createSetObject(void) {
    dict *d = dictCreate(&setDictType);
    robj *o = createObject(OBJ_SET,d);
    o->encoding = OBJ_ENCODING_HT;
    return o;
}

robj *createIntsetObject(void) {
    intset *is = intsetNew();
    robj *o = createObject(OBJ_SET,is);
    o->encoding = OBJ_ENCODING_INTSET;
    return o;
}

robj *createSetListpackObject(void) {
    unsigned char *lp = lpNew(0);
    robj *o = createObject(OBJ_SET, lp);
    o->encoding = OBJ_ENCODING_LISTPACK;
    return o;
}

robj *createHashObject(void) {
    unsigned char *zl = lpNew(0);
    robj *o = createObject(OBJ_HASH, zl);
    o->encoding = OBJ_ENCODING_LISTPACK;
    return o;
}

robj *createZsetObject(void) {
    zset *zs = zmalloc(sizeof(*zs));
    robj *o;

    zs->dict = dictCreate(&zsetDictType);
    zs->zsl = zslCreate();
    o = createObject(OBJ_ZSET,zs);
    o->encoding = OBJ_ENCODING_SKIPLIST;
    return o;
}

robj *createZsetListpackObject(void) {
    unsigned char *lp = lpNew(0);
    robj *o = createObject(OBJ_ZSET,lp);
    o->encoding = OBJ_ENCODING_LISTPACK;
    return o;
}

robj *createStreamObject(void) {
    stream *s = streamNew();
    robj *o = createObject(OBJ_STREAM,s);
    o->encoding = OBJ_ENCODING_STREAM;
    return o;
}

robj *createModuleObject(moduleType *mt, void *value) {
    moduleValue *mv = zmalloc(sizeof(*mv));
    mv->type = mt;
    mv->value = value;
    return createObject(OBJ_MODULE,mv);
}

void freeStringObject(robj *o) {
    if (o->encoding == OBJ_ENCODING_RAW) {
        sdsfree(o->ptr);
    }
}

void freeListObject(robj *o) {
    if (o->encoding == OBJ_ENCODING_QUICKLIST) {
        quicklistRelease(o->ptr);
    } else if (o->encoding == OBJ_ENCODING_LISTPACK) {
        lpFree(o->ptr);
    } else {
        serverPanic("Unknown list encoding type");
    }
}

void freeSetObject(robj *o) {
    switch (o->encoding) {
    case OBJ_ENCODING_HT:
        dictRelease((dict*) o->ptr);
        break;
    case OBJ_ENCODING_INTSET:
    case OBJ_ENCODING_LISTPACK:
        zfree(o->ptr);
        break;
    default:
        serverPanic("Unknown set encoding type");
    }
}

void freeZsetObject(robj *o) {
    zset *zs;
    switch (o->encoding) {
    case OBJ_ENCODING_SKIPLIST:
        zs = o->ptr;
        dictRelease(zs->dict);
        zslFree(zs->zsl);
        zfree(zs);
        break;
    case OBJ_ENCODING_LISTPACK:
        zfree(o->ptr);
        break;
    default:
        serverPanic("Unknown sorted set encoding");
    }
}

void freeHashObject(robj *o) {
    switch (o->encoding) {
    case OBJ_ENCODING_HT:
        dictRelease((dict*) o->ptr);
        break;
    case OBJ_ENCODING_LISTPACK:
        lpFree(o->ptr);
        break;
    default:
        serverPanic("Unknown hash encoding type");
        break;
    }
}

void freeModuleObject(robj *o) {
    moduleValue *mv = o->ptr;
    mv->type->free(mv->value);
    zfree(mv);
}

void freeStreamObject(robj *o) {
    freeStream(o->ptr);
}

void incrRefCount(robj *o) {
    if (o->refcount < OBJ_FIRST_SPECIAL_REFCOUNT) {
        o->refcount++;
    } else {
        if (o->refcount == OBJ_SHARED_REFCOUNT) {
            /* Nothing to do: this refcount is immutable. */
        } else if (o->refcount == OBJ_STATIC_REFCOUNT) {
            serverPanic("You tried to retain an object allocated in the stack");
        }
    }
}

void decrRefCount(robj *o) {
    if (o->refcount == 1) {
        switch(o->type) {
        case OBJ_STRING: freeStringObject(o); break;
        case OBJ_LIST: freeListObject(o); break;
        case OBJ_SET: freeSetObject(o); break;
        case OBJ_ZSET: freeZsetObject(o); break;
        case OBJ_HASH: freeHashObject(o); break;
        case OBJ_MODULE: freeModuleObject(o); break;
        case OBJ_STREAM: freeStreamObject(o); break;
        default: serverPanic("Unknown object type"); break;
        }
        zfree(o);
    } else {
        if (o->refcount <= 0) serverPanic("decrRefCount against refcount <= 0");
        if (o->refcount != OBJ_SHARED_REFCOUNT) o->refcount--;
    }
}

/* See dismissObject() */
void dismissSds(sds s) {
    dismissMemory(sdsAllocPtr(s), sdsAllocSize(s));
}

/* See dismissObject() */
void dismissStringObject(robj *o) {
    if (o->encoding == OBJ_ENCODING_RAW) {
        dismissSds(o->ptr);
    }
}

/* See dismissObject() */
void dismissListObject(robj *o, size_t size_hint) {
    if (o->encoding == OBJ_ENCODING_QUICKLIST) {
        quicklist *ql = o->ptr;
        serverAssert(ql->len != 0);
        /* We iterate all nodes only when average node size is bigger than a
         * page size, and there's a high chance we'll actually dismiss something. */
        if (size_hint / ql->len >= server.page_size) {
            quicklistNode *node = ql->head;
            while (node) {
                if (quicklistNodeIsCompressed(node)) {
                    dismissMemory(node->entry, ((quicklistLZF*)node->entry)->sz);
                } else {
                    dismissMemory(node->entry, node->sz);
                }
                node = node->next;
            }
        }
    } else if (o->encoding == OBJ_ENCODING_LISTPACK) {
        dismissMemory(o->ptr, lpBytes((unsigned char*)o->ptr));
    } else {
        serverPanic("Unknown list encoding type");
    }
}

/* See dismissObject() */
void dismissSetObject(robj *o, size_t size_hint) {
    if (o->encoding == OBJ_ENCODING_HT) {
        dict *set = o->ptr;
        serverAssert(dictSize(set) != 0);
        /* We iterate all nodes only when average member size is bigger than a
         * page size, and there's a high chance we'll actually dismiss something. */
        if (size_hint / dictSize(set) >= server.page_size) {
            dictEntry *de;
            dictIterator *di = dictGetIterator(set);
            while ((de = dictNext(di)) != NULL) {
                dismissSds(dictGetKey(de));
            }
            dictReleaseIterator(di);
        }

        /* Dismiss hash table memory. */
        dismissMemory(set->ht_table[0], DICTHT_SIZE(set->ht_size_exp[0])*sizeof(dictEntry*));
        dismissMemory(set->ht_table[1], DICTHT_SIZE(set->ht_size_exp[1])*sizeof(dictEntry*));
    } else if (o->encoding == OBJ_ENCODING_INTSET) {
        dismissMemory(o->ptr, intsetBlobLen((intset*)o->ptr));
    } else if (o->encoding == OBJ_ENCODING_LISTPACK) {
        dismissMemory(o->ptr, lpBytes((unsigned char *)o->ptr));
    } else {
        serverPanic("Unknown set encoding type");
    }
}

/* See dismissObject() */
void dismissZsetObject(robj *o, size_t size_hint) {
    if (o->encoding == OBJ_ENCODING_SKIPLIST) {
        zset *zs = o->ptr;
        zskiplist *zsl = zs->zsl;
        serverAssert(zsl->length != 0);
        /* We iterate all nodes only when average member size is bigger than a
         * page size, and there's a high chance we'll actually dismiss something. */
        if (size_hint / zsl->length >= server.page_size) {
            zskiplistNode *zn = zsl->tail;
            while (zn != NULL) {
                dismissSds(zn->ele);
                zn = zn->backward;
            }
        }

        /* Dismiss hash table memory. */
        dict *d = zs->dict;
        dismissMemory(d->ht_table[0], DICTHT_SIZE(d->ht_size_exp[0])*sizeof(dictEntry*));
        dismissMemory(d->ht_table[1], DICTHT_SIZE(d->ht_size_exp[1])*sizeof(dictEntry*));
    } else if (o->encoding == OBJ_ENCODING_LISTPACK) {
        dismissMemory(o->ptr, lpBytes((unsigned char*)o->ptr));
    } else {
        serverPanic("Unknown zset encoding type");
    }
}

/* See dismissObject() */
void dismissHashObject(robj *o, size_t size_hint) {
    if (o->encoding == OBJ_ENCODING_HT) {
        dict *d = o->ptr;
        serverAssert(dictSize(d) != 0);
        /* We iterate all fields only when average field/value size is bigger than
         * a page size, and there's a high chance we'll actually dismiss something. */
        if (size_hint / dictSize(d) >= server.page_size) {
            dictEntry *de;
            dictIterator *di = dictGetIterator(d);
            while ((de = dictNext(di)) != NULL) {
                /* Only dismiss values memory since the field size
                 * usually is small. */
                dismissSds(dictGetVal(de));
            }
            dictReleaseIterator(di);
        }

        /* Dismiss hash table memory. */
        dismissMemory(d->ht_table[0], DICTHT_SIZE(d->ht_size_exp[0])*sizeof(dictEntry*));
        dismissMemory(d->ht_table[1], DICTHT_SIZE(d->ht_size_exp[1])*sizeof(dictEntry*));
    } else if (o->encoding == OBJ_ENCODING_LISTPACK) {
        dismissMemory(o->ptr, lpBytes((unsigned char*)o->ptr));
    } else {
        serverPanic("Unknown hash encoding type");
    }
}

/* See dismissObject() */
void dismissStreamObject(robj *o, size_t size_hint) {
    stream *s = o->ptr;
    rax *rax = s->rax;
    if (raxSize(rax) == 0) return;

    /* Iterate only on stream entries, although size_hint may include serialized
     * consumer groups info, but usually, stream entries take up most of
     * the space. */
    if (size_hint / raxSize(rax) >= server.page_size) {
        raxIterator ri;
        raxStart(&ri,rax);
        raxSeek(&ri,"^",NULL,0);
        while (raxNext(&ri)) {
            dismissMemory(ri.data, lpBytes(ri.data));
        }
        raxStop(&ri);
    }
}

/* When creating a snapshot in a fork child process, the main process and child
 * process share the same physical memory pages, and if / when the parent
 * modifies any keys due to write traffic, it'll cause CoW which consume
 * physical memory. In the child process, after serializing the key and value,
 * the data is definitely not accessed again, so to avoid unnecessary CoW, we
 * try to release their memory back to OS. see dismissMemory().
 *
 * Because of the cost of iterating all node/field/member/entry of complex data
 * types, we iterate and dismiss them only when approximate average we estimate
 * the size of an individual allocation is more than a page size of OS.
 * 'size_hint' is the size of serialized value. This method is not accurate, but
 * it can reduce unnecessary iteration for complex data types that are probably
 * not going to release any memory. */
void dismissObject(robj *o, size_t size_hint) {
    /* madvise(MADV_DONTNEED) may not work if Transparent Huge Pages is enabled. */
    if (server.thp_enabled) return;

    /* Currently we use zmadvise_dontneed only when we use jemalloc with Linux.
     * so we avoid these pointless loops when they're not going to do anything. */
#if defined(USE_JEMALLOC) && defined(__linux__)
    if (o->refcount != 1) return;
    switch(o->type) {
        case OBJ_STRING: dismissStringObject(o); break;
        case OBJ_LIST: dismissListObject(o, size_hint); break;
        case OBJ_SET: dismissSetObject(o, size_hint); break;
        case OBJ_ZSET: dismissZsetObject(o, size_hint); break;
        case OBJ_HASH: dismissHashObject(o, size_hint); break;
        case OBJ_STREAM: dismissStreamObject(o, size_hint); break;
        default: break;
    }
#else
    UNUSED(o); UNUSED(size_hint);
#endif
}

/* This variant of decrRefCount() gets its argument as void, and is useful
 * as free method in data structures that expect a 'void free_object(void*)'
 * prototype for the free method. */
void decrRefCountVoid(void *o) {
    decrRefCount(o);
}

int checkType(client *c, robj *o, int type) {
    /* A NULL is considered an empty key */
    if (o && o->type != type) {
        addReplyErrorObject(c,shared.wrongtypeerr);
        return 1;
    }
    return 0;
}

int isSdsRepresentableAsLongLong(sds s, long long *llval) {
    return string2ll(s,sdslen(s),llval) ? C_OK : C_ERR;
}

int isObjectRepresentableAsLongLong(robj *o, long long *llval) {
    serverAssertWithInfo(NULL,o,o->type == OBJ_STRING);
    if (o->encoding == OBJ_ENCODING_INT) {
        if (llval) *llval = (long) o->ptr;
        return C_OK;
    } else {
        return isSdsRepresentableAsLongLong(o->ptr,llval);
    }
}

/* Optimize the SDS string inside the string object to require little space,
 * in case there is more than 10% of free space at the end of the SDS. */
void trimStringObjectIfNeeded(robj *o, int trim_small_values) {
    if (o->encoding != OBJ_ENCODING_RAW) return;
    /* A string may have free space in the following cases:
     * 1. When an arg len is greater than PROTO_MBULK_BIG_ARG the query buffer may be used directly as the SDS string.
     * 2. When utilizing the argument caching mechanism in Lua. 
     * 3. When calling from RM_TrimStringAllocation (trim_small_values is true). */
    size_t len = sdslen(o->ptr);
    if (len >= PROTO_MBULK_BIG_ARG ||
        trim_small_values||
        (server.executing_client && server.executing_client->flags & CLIENT_SCRIPT && len < LUA_CMD_OBJCACHE_MAX_LEN)) {
        if (sdsavail(o->ptr) > len/10) {
            o->ptr = sdsRemoveFreeSpace(o->ptr, 0);
        }
    }
}

/* Try to encode a string object in order to save space */
robj *tryObjectEncodingEx(robj *o, int try_trim) {
    long value;
    sds s = o->ptr;
    size_t len;

    /* Make sure this is a string object, the only type we encode
     * in this function. Other types use encoded memory efficient
     * representations but are handled by the commands implementing
     * the type. */
    serverAssertWithInfo(NULL,o,o->type == OBJ_STRING);

    /* We try some specialized encoding only for objects that are
     * RAW or EMBSTR encoded, in other words objects that are still
     * in represented by an actually array of chars. */
    if (!sdsEncodedObject(o)) return o;

    /* It's not safe to encode shared objects: shared objects can be shared
     * everywhere in the "object space" of Redis and may end in places where
     * they are not handled. We handle them only as values in the keyspace. */
     if (o->refcount > 1) return o;

    /* Check if we can represent this string as a long integer.
     * Note that we are sure that a string larger than 20 chars is not
     * representable as a 32 nor 64 bit integer. */
    len = sdslen(s);
    if (len <= 20 && string2l(s,len,&value)) {
        /* This object is encodable as a long. Try to use a shared object.
         * Note that we avoid using shared integers when maxmemory is used
         * because every object needs to have a private LRU field for the LRU
         * algorithm to work well. */
        if ((server.maxmemory == 0 ||
            !(server.maxmemory_policy & MAXMEMORY_FLAG_NO_SHARED_INTEGERS)) &&
            value >= 0 &&
            value < OBJ_SHARED_INTEGERS)
        {
            decrRefCount(o);
            return shared.integers[value];
        } else {
            if (o->encoding == OBJ_ENCODING_RAW) {
                sdsfree(o->ptr);
                o->encoding = OBJ_ENCODING_INT;
                o->ptr = (void*) value;
                return o;
            } else if (o->encoding == OBJ_ENCODING_EMBSTR) {
                decrRefCount(o);
                return createStringObjectFromLongLongForValue(value);
            }
        }
    }

    /* If the string is small and is still RAW encoded,
     * try the EMBSTR encoding which is more efficient.
     * In this representation the object and the SDS string are allocated
     * in the same chunk of memory to save space and cache misses. */
    if (len <= OBJ_ENCODING_EMBSTR_SIZE_LIMIT) {
        robj *emb;

        if (o->encoding == OBJ_ENCODING_EMBSTR) return o;
        emb = createEmbeddedStringObject(s,sdslen(s));
        decrRefCount(o);
        return emb;
    }

    /* We can't encode the object...
     * Do the last try, and at least optimize the SDS string inside */
    if (try_trim)
        trimStringObjectIfNeeded(o, 0);

    /* Return the original object. */
    return o;
}

robj *tryObjectEncoding(robj *o) {
    return tryObjectEncodingEx(o, 1);
}

/* Get a decoded version of an encoded object (returned as a new object).
 * If the object is already raw-encoded just increment the ref count. */
robj *getDecodedObject(robj *o) {
    robj *dec;

    if (sdsEncodedObject(o)) {
        incrRefCount(o);
        return o;
    }
    if (o->type == OBJ_STRING && o->encoding == OBJ_ENCODING_INT) {
        char buf[32];

        ll2string(buf,32,(long)o->ptr);
        dec = createStringObject(buf,strlen(buf));
        return dec;
    } else {
        serverPanic("Unknown encoding type");
    }
}

/* Compare two string objects via strcmp() or strcoll() depending on flags.
 * Note that the objects may be integer-encoded. In such a case we
 * use ll2string() to get a string representation of the numbers on the stack
 * and compare the strings, it's much faster than calling getDecodedObject().
 *
 * Important note: when REDIS_COMPARE_BINARY is used a binary-safe comparison
 * is used. */

#define REDIS_COMPARE_BINARY (1<<0)
#define REDIS_COMPARE_COLL (1<<1)

int compareStringObjectsWithFlags(const robj *a, const robj *b, int flags) {
    serverAssertWithInfo(NULL,a,a->type == OBJ_STRING && b->type == OBJ_STRING);
    char bufa[128], bufb[128], *astr, *bstr;
    size_t alen, blen, minlen;

    if (a == b) return 0;
    if (sdsEncodedObject(a)) {
        astr = a->ptr;
        alen = sdslen(astr);
    } else {
        alen = ll2string(bufa,sizeof(bufa),(long) a->ptr);
        astr = bufa;
    }
    if (sdsEncodedObject(b)) {
        bstr = b->ptr;
        blen = sdslen(bstr);
    } else {
        blen = ll2string(bufb,sizeof(bufb),(long) b->ptr);
        bstr = bufb;
    }
    if (flags & REDIS_COMPARE_COLL) {
        return strcoll(astr,bstr);
    } else {
        int cmp;

        minlen = (alen < blen) ? alen : blen;
        cmp = memcmp(astr,bstr,minlen);
        if (cmp == 0) return alen-blen;
        return cmp;
    }
}

/* Wrapper for compareStringObjectsWithFlags() using binary comparison. */
int compareStringObjects(const robj *a, const robj *b) {
    return compareStringObjectsWithFlags(a,b,REDIS_COMPARE_BINARY);
}

/* Wrapper for compareStringObjectsWithFlags() using collation. */
int collateStringObjects(const robj *a, const robj *b) {
    return compareStringObjectsWithFlags(a,b,REDIS_COMPARE_COLL);
}

/* Equal string objects return 1 if the two objects are the same from the
 * point of view of a string comparison, otherwise 0 is returned. Note that
 * this function is faster then checking for (compareStringObject(a,b) == 0)
 * because it can perform some more optimization. */
int equalStringObjects(robj *a, robj *b) {
    if (a->encoding == OBJ_ENCODING_INT &&
        b->encoding == OBJ_ENCODING_INT){
        /* If both strings are integer encoded just check if the stored
         * long is the same. */
        return a->ptr == b->ptr;
    } else {
        return compareStringObjects(a,b) == 0;
    }
}

size_t stringObjectLen(robj *o) {
    serverAssertWithInfo(NULL,o,o->type == OBJ_STRING);
    if (sdsEncodedObject(o)) {
        return sdslen(o->ptr);
    } else {
        return sdigits10((long)o->ptr);
    }
}

int getDoubleFromObject(const robj *o, double *target) {
    double value;

    if (o == NULL) {
        value = 0;
    } else {
        serverAssertWithInfo(NULL,o,o->type == OBJ_STRING);
        if (sdsEncodedObject(o)) {
            if (!string2d(o->ptr, sdslen(o->ptr), &value))
                return C_ERR;
        } else if (o->encoding == OBJ_ENCODING_INT) {
            value = (long)o->ptr;
        } else {
            serverPanic("Unknown string encoding");
        }
    }
    *target = value;
    return C_OK;
}

int getDoubleFromObjectOrReply(client *c, robj *o, double *target, const char *msg) {
    double value;
    if (getDoubleFromObject(o, &value) != C_OK) {
        if (msg != NULL) {
            addReplyError(c,(char*)msg);
        } else {
            addReplyError(c,"value is not a valid float");
        }
        return C_ERR;
    }
    *target = value;
    return C_OK;
}

int getLongDoubleFromObject(robj *o, long double *target) {
    long double value;

    if (o == NULL) {
        value = 0;
    } else {
        serverAssertWithInfo(NULL,o,o->type == OBJ_STRING);
        if (sdsEncodedObject(o)) {
            if (!string2ld(o->ptr, sdslen(o->ptr), &value))
                return C_ERR;
        } else if (o->encoding == OBJ_ENCODING_INT) {
            value = (long)o->ptr;
        } else {
            serverPanic("Unknown string encoding");
        }
    }
    *target = value;
    return C_OK;
}

int getLongDoubleFromObjectOrReply(client *c, robj *o, long double *target, const char *msg) {
    long double value;
    if (getLongDoubleFromObject(o, &value) != C_OK) {
        if (msg != NULL) {
            addReplyError(c,(char*)msg);
        } else {
            addReplyError(c,"value is not a valid float");
        }
        return C_ERR;
    }
    *target = value;
    return C_OK;
}

int getLongLongFromObject(robj *o, long long *target) {
    long long value;

    if (o == NULL) {
        value = 0;
    } else {
        serverAssertWithInfo(NULL,o,o->type == OBJ_STRING);
        if (sdsEncodedObject(o)) {
            if (string2ll(o->ptr,sdslen(o->ptr),&value) == 0) return C_ERR;
        } else if (o->encoding == OBJ_ENCODING_INT) {
            value = (long)o->ptr;
        } else {
            serverPanic("Unknown string encoding");
        }
    }
    if (target) *target = value;
    return C_OK;
}

int getLongLongFromObjectOrReply(client *c, robj *o, long long *target, const char *msg) {
    long long value;
    if (getLongLongFromObject(o, &value) != C_OK) {
        if (msg != NULL) {
            addReplyError(c,(char*)msg);
        } else {
            addReplyError(c,"value is not an integer or out of range");
        }
        return C_ERR;
    }
    *target = value;
    return C_OK;
}

int getLongFromObjectOrReply(client *c, robj *o, long *target, const char *msg) {
    long long value;

    if (getLongLongFromObjectOrReply(c, o, &value, msg) != C_OK) return C_ERR;
    if (value < LONG_MIN || value > LONG_MAX) {
        if (msg != NULL) {
            addReplyError(c,(char*)msg);
        } else {
            addReplyError(c,"value is out of range");
        }
        return C_ERR;
    }
    *target = value;
    return C_OK;
}

int getRangeLongFromObjectOrReply(client *c, robj *o, long min, long max, long *target, const char *msg) {
    if (getLongFromObjectOrReply(c, o, target, msg) != C_OK) return C_ERR;
    if (*target < min || *target > max) {
        if (msg != NULL) {
            addReplyError(c,(char*)msg);
        } else {
            addReplyErrorFormat(c,"value is out of range, value must between %ld and %ld", min, max);
        }
        return C_ERR;
    }
    return C_OK;
}

int getPositiveLongFromObjectOrReply(client *c, robj *o, long *target, const char *msg) {
    if (msg) {
        return getRangeLongFromObjectOrReply(c, o, 0, LONG_MAX, target, msg);
    } else {
        return getRangeLongFromObjectOrReply(c, o, 0, LONG_MAX, target, "value is out of range, must be positive");
    }
}

int getIntFromObjectOrReply(client *c, robj *o, int *target, const char *msg) {
    long value;

    if (getRangeLongFromObjectOrReply(c, o, INT_MIN, INT_MAX, &value, msg) != C_OK)
        return C_ERR;

    *target = value;
    return C_OK;
}

char *strEncoding(int encoding) {
    switch(encoding) {
    case OBJ_ENCODING_RAW: return "raw";
    case OBJ_ENCODING_INT: return "int";
    case OBJ_ENCODING_HT: return "hashtable";
    case OBJ_ENCODING_QUICKLIST: return "quicklist";
    case OBJ_ENCODING_LISTPACK: return "listpack";
    case OBJ_ENCODING_INTSET: return "intset";
    case OBJ_ENCODING_SKIPLIST: return "skiplist";
    case OBJ_ENCODING_EMBSTR: return "embstr";
    case OBJ_ENCODING_STREAM: return "stream";
    default: return "unknown";
    }
}

/* =========================== Memory introspection ========================= */


/* This is a helper function with the goal of estimating the memory
 * size of a radix tree that is used to store Stream IDs.
 *
 * Note: to guess the size of the radix tree is not trivial, so we
 * approximate it considering 16 bytes of data overhead for each
 * key (the ID), and then adding the number of bare nodes, plus some
 * overhead due by the data and child pointers. This secret recipe
 * was obtained by checking the average radix tree created by real
 * workloads, and then adjusting the constants to get numbers that
 * more or less match the real memory usage.
 *
 * Actually the number of nodes and keys may be different depending
 * on the insertion speed and thus the ability of the radix tree
 * to compress prefixes. */
size_t streamRadixTreeMemoryUsage(rax *rax) {
    size_t size = sizeof(*rax);
    size = rax->numele * sizeof(streamID);
    size += rax->numnodes * sizeof(raxNode);
    /* Add a fixed overhead due to the aux data pointer, children, ... */
    size += rax->numnodes * sizeof(long)*30;
    return size;
}

/* Returns the size in bytes consumed by the key's value in RAM.
 * Note that the returned value is just an approximation, especially in the
 * case of aggregated data types where only "sample_size" elements
 * are checked and averaged to estimate the total size. */
#define OBJ_COMPUTE_SIZE_DEF_SAMPLES 5 /* Default sample size. */
size_t objectComputeSize(robj *key, robj *o, size_t sample_size, int dbid) {
    sds ele, ele2;
    dict *d;
    dictIterator *di;
    struct dictEntry *de;
    size_t asize = 0, elesize = 0, samples = 0;

    if (o->type == OBJ_STRING) {
        if(o->encoding == OBJ_ENCODING_INT) {
            asize = sizeof(*o);
        } else if(o->encoding == OBJ_ENCODING_RAW) {
            asize = sdsZmallocSize(o->ptr)+sizeof(*o);
        } else if(o->encoding == OBJ_ENCODING_EMBSTR) {
            asize = zmalloc_size((void *)o);
        } else {
            serverPanic("Unknown string encoding");
        }
    } else if (o->type == OBJ_LIST) {
        if (o->encoding == OBJ_ENCODING_QUICKLIST) {
            quicklist *ql = o->ptr;
            quicklistNode *node = ql->head;
            asize = sizeof(*o)+sizeof(quicklist);
            do {
                elesize += sizeof(quicklistNode)+zmalloc_size(node->entry);
                samples++;
            } while ((node = node->next) && samples < sample_size);
            asize += (double)elesize/samples*ql->len;
        } else if (o->encoding == OBJ_ENCODING_LISTPACK) {
            asize = sizeof(*o)+zmalloc_size(o->ptr);
        } else {
            serverPanic("Unknown list encoding");
        }
    } else if (o->type == OBJ_SET) {
        if (o->encoding == OBJ_ENCODING_HT) {
            d = o->ptr;
            di = dictGetIterator(d);
            asize = sizeof(*o)+sizeof(dict)+(sizeof(struct dictEntry*)*dictSlots(d));
            while((de = dictNext(di)) != NULL && samples < sample_size) {
                ele = dictGetKey(de);
                elesize += dictEntryMemUsage() + sdsZmallocSize(ele);
                samples++;
            }
            dictReleaseIterator(di);
            if (samples) asize += (double)elesize/samples*dictSize(d);
        } else if (o->encoding == OBJ_ENCODING_INTSET) {
            asize = sizeof(*o)+zmalloc_size(o->ptr);
        } else if (o->encoding == OBJ_ENCODING_LISTPACK) {
            asize = sizeof(*o)+zmalloc_size(o->ptr);
        } else {
            serverPanic("Unknown set encoding");
        }
    } else if (o->type == OBJ_ZSET) {
        if (o->encoding == OBJ_ENCODING_LISTPACK) {
            asize = sizeof(*o)+zmalloc_size(o->ptr);
        } else if (o->encoding == OBJ_ENCODING_SKIPLIST) {
            d = ((zset*)o->ptr)->dict;
            zskiplist *zsl = ((zset*)o->ptr)->zsl;
            zskiplistNode *znode = zsl->header->level[0].forward;
            asize = sizeof(*o)+sizeof(zset)+sizeof(zskiplist)+sizeof(dict)+
                    (sizeof(struct dictEntry*)*dictSlots(d))+
                    zmalloc_size(zsl->header);
            while(znode != NULL && samples < sample_size) {
                elesize += sdsZmallocSize(znode->ele);
                elesize += dictEntryMemUsage()+zmalloc_size(znode);
                samples++;
                znode = znode->level[0].forward;
            }
            if (samples) asize += (double)elesize/samples*dictSize(d);
        } else {
            serverPanic("Unknown sorted set encoding");
        }
    } else if (o->type == OBJ_HASH) {
        if (o->encoding == OBJ_ENCODING_LISTPACK) {
            asize = sizeof(*o)+zmalloc_size(o->ptr);
        } else if (o->encoding == OBJ_ENCODING_HT) {
            d = o->ptr;
            di = dictGetIterator(d);
            asize = sizeof(*o)+sizeof(dict)+(sizeof(struct dictEntry*)*dictSlots(d));
            while((de = dictNext(di)) != NULL && samples < sample_size) {
                ele = dictGetKey(de);
                ele2 = dictGetVal(de);
                elesize += sdsZmallocSize(ele) + sdsZmallocSize(ele2);
                elesize += dictEntryMemUsage();
                samples++;
            }
            dictReleaseIterator(di);
            if (samples) asize += (double)elesize/samples*dictSize(d);
        } else {
            serverPanic("Unknown hash encoding");
        }
    } else if (o->type == OBJ_STREAM) {
        stream *s = o->ptr;
        asize = sizeof(*o)+sizeof(*s);
        asize += streamRadixTreeMemoryUsage(s->rax);

        /* Now we have to add the listpacks. The last listpack is often non
         * complete, so we estimate the size of the first N listpacks, and
         * use the average to compute the size of the first N-1 listpacks, and
         * finally add the real size of the last node. */
        raxIterator ri;
        raxStart(&ri,s->rax);
        raxSeek(&ri,"^",NULL,0);
        size_t lpsize = 0, samples = 0;
        while(samples < sample_size && raxNext(&ri)) {
            unsigned char *lp = ri.data;
            /* Use the allocated size, since we overprovision the node initially. */
            lpsize += zmalloc_size(lp);
            samples++;
        }
        if (s->rax->numele <= samples) {
            asize += lpsize;
        } else {
            if (samples) lpsize /= samples; /* Compute the average. */
            asize += lpsize * (s->rax->numele-1);
            /* No need to check if seek succeeded, we enter this branch only
             * if there are a few elements in the radix tree. */
            raxSeek(&ri,"$",NULL,0);
            raxNext(&ri);
            /* Use the allocated size, since we overprovision the node initially. */
            asize += zmalloc_size(ri.data);
        }
        raxStop(&ri);

        /* Consumer groups also have a non trivial memory overhead if there
         * are many consumers and many groups, let's count at least the
         * overhead of the pending entries in the groups and consumers
         * PELs. */
        if (s->cgroups) {
            raxStart(&ri,s->cgroups);
            raxSeek(&ri,"^",NULL,0);
            while(raxNext(&ri)) {
                streamCG *cg = ri.data;
                asize += sizeof(*cg);
                asize += streamRadixTreeMemoryUsage(cg->pel);
                asize += sizeof(streamNACK)*raxSize(cg->pel);

                /* For each consumer we also need to add the basic data
                 * structures and the PEL memory usage. */
                raxIterator cri;
                raxStart(&cri,cg->consumers);
                raxSeek(&cri,"^",NULL,0);
                while(raxNext(&cri)) {
                    streamConsumer *consumer = cri.data;
                    asize += sizeof(*consumer);
                    asize += sdslen(consumer->name);
                    asize += streamRadixTreeMemoryUsage(consumer->pel);
                    /* Don't count NACKs again, they are shared with the
                     * consumer group PEL. */
                }
                raxStop(&cri);
            }
            raxStop(&ri);
        }
    } else if (o->type == OBJ_MODULE) {
        asize = moduleGetMemUsage(key, o, sample_size, dbid);
    } else {
        serverPanic("Unknown object type");
    }
    return asize;
}

/* Release data obtained with getMemoryOverheadData(). */
void freeMemoryOverheadData(struct redisMemOverhead *mh) {
    zfree(mh->db);
    zfree(mh);
}

/* Return a struct redisMemOverhead filled with memory overhead
 * information used for the MEMORY OVERHEAD and INFO command. The returned
 * structure pointer should be freed calling freeMemoryOverheadData(). */
struct redisMemOverhead *getMemoryOverheadData(void) {
    int j;
    size_t mem_total = 0;
    size_t mem = 0;
    size_t zmalloc_used = zmalloc_used_memory();
    struct redisMemOverhead *mh = zcalloc(sizeof(*mh));

    mh->total_allocated = zmalloc_used;
    mh->startup_allocated = server.initial_memory_usage;
    mh->peak_allocated = server.stat_peak_memory;
    mh->total_frag =
        (float)server.cron_malloc_stats.process_rss / server.cron_malloc_stats.zmalloc_used;
    mh->total_frag_bytes =
        server.cron_malloc_stats.process_rss - server.cron_malloc_stats.zmalloc_used;
    mh->allocator_frag =
        (float)server.cron_malloc_stats.allocator_active / server.cron_malloc_stats.allocator_allocated;
    mh->allocator_frag_bytes =
        server.cron_malloc_stats.allocator_active - server.cron_malloc_stats.allocator_allocated;
    mh->allocator_rss =
        (float)server.cron_malloc_stats.allocator_resident / server.cron_malloc_stats.allocator_active;
    mh->allocator_rss_bytes =
        server.cron_malloc_stats.allocator_resident - server.cron_malloc_stats.allocator_active;
    mh->rss_extra =
        (float)server.cron_malloc_stats.process_rss / server.cron_malloc_stats.allocator_resident;
    mh->rss_extra_bytes =
        server.cron_malloc_stats.process_rss - server.cron_malloc_stats.allocator_resident;

    mem_total += server.initial_memory_usage;

    /* Replication backlog and replicas share one global replication buffer,
     * only if replication buffer memory is more than the repl backlog setting,
     * we consider the excess as replicas' memory. Otherwise, replication buffer
     * memory is the consumption of repl backlog. */
    if (listLength(server.slaves) &&
        (long long)server.repl_buffer_mem > server.repl_backlog_size)
    {
        mh->clients_slaves = server.repl_buffer_mem - server.repl_backlog_size;
        mh->repl_backlog = server.repl_backlog_size;
    } else {
        mh->clients_slaves = 0;
        mh->repl_backlog = server.repl_buffer_mem;
    }
    if (server.repl_backlog) {
        /* The approximate memory of rax tree for indexed blocks. */
        mh->repl_backlog +=
            server.repl_backlog->blocks_index->numnodes * sizeof(raxNode) +
            raxSize(server.repl_backlog->blocks_index) * sizeof(void*);
    }
    mem_total += mh->repl_backlog;
    mem_total += mh->clients_slaves;

    /* Computing the memory used by the clients would be O(N) if done
     * here online. We use our values computed incrementally by
     * updateClientMemoryUsage(). */
    mh->clients_normal = server.stat_clients_type_memory[CLIENT_TYPE_MASTER]+
                         server.stat_clients_type_memory[CLIENT_TYPE_PUBSUB]+
                         server.stat_clients_type_memory[CLIENT_TYPE_NORMAL];
    mem_total += mh->clients_normal;

    mh->cluster_links = server.stat_cluster_links_memory;
    mem_total += mh->cluster_links;

    mem = 0;
    if (server.aof_state != AOF_OFF) {
        mem += sdsZmallocSize(server.aof_buf);
    }
    mh->aof_buffer = mem;
    mem_total+=mem;

    mem = evalScriptsMemory();
    mh->lua_caches = mem;
    mem_total+=mem;
    mh->functions_caches = functionsMemoryOverhead();
    mem_total+=mh->functions_caches;

    for (j = 0; j < server.dbnum; j++) {
        redisDb *db = server.db+j;
        long long keyscount = dictSize(db->dict);
        if (keyscount==0) continue;

        mh->total_keys += keyscount;
        mh->db = zrealloc(mh->db,sizeof(mh->db[0])*(mh->num_dbs+1));
        mh->db[mh->num_dbs].dbid = j;

        mem = dictMemUsage(db->dict) +
              dictSize(db->dict) * sizeof(robj);
        mh->db[mh->num_dbs].overhead_ht_main = mem;
        mem_total+=mem;

        mem = dictMemUsage(db->expires);
        mh->db[mh->num_dbs].overhead_ht_expires = mem;
        mem_total+=mem;

        /* Account for the slot to keys map in cluster mode */
        mem = dictSize(db->dict) * dictEntryMetadataSize(db->dict) +
              dictMetadataSize(db->dict);
        mh->db[mh->num_dbs].overhead_ht_slot_to_keys = mem;
        mem_total+=mem;

        mh->num_dbs++;
    }

    mh->overhead_total = mem_total;
    mh->dataset = zmalloc_used - mem_total;
    mh->peak_perc = (float)zmalloc_used*100/mh->peak_allocated;

    /* Metrics computed after subtracting the startup memory from
     * the total memory. */
    size_t net_usage = 1;
    if (zmalloc_used > mh->startup_allocated)
        net_usage = zmalloc_used - mh->startup_allocated;
    mh->dataset_perc = (float)mh->dataset*100/net_usage;
    mh->bytes_per_key = mh->total_keys ? (net_usage / mh->total_keys) : 0;

    return mh;
}

/* Helper for "MEMORY allocator-stats", used as a callback for the jemalloc
 * stats output. */
void inputCatSds(void *result, const char *str) {
    /* result is actually a (sds *), so re-cast it here */
    sds *info = (sds *)result;
    *info = sdscat(*info, str);
}

/* This implements MEMORY DOCTOR. An human readable analysis of the Redis
 * memory condition. */
sds getMemoryDoctorReport(void) {
    int empty = 0;          /* Instance is empty or almost empty. */
    int big_peak = 0;       /* Memory peak is much larger than used mem. */
    int high_frag = 0;      /* High fragmentation. */
    int high_alloc_frag = 0;/* High allocator fragmentation. */
    int high_proc_rss = 0;  /* High process rss overhead. */
    int high_alloc_rss = 0; /* High rss overhead. */
    int big_slave_buf = 0;  /* Slave buffers are too big. */
    int big_client_buf = 0; /* Client buffers are too big. */
    int many_scripts = 0;   /* Script cache has too many scripts. */
    int num_reports = 0;
    struct redisMemOverhead *mh = getMemoryOverheadData();

    if (mh->total_allocated < (1024*1024*5)) {
        empty = 1;
        num_reports++;
    } else {
        /* Peak is > 150% of current used memory? */
        if (((float)mh->peak_allocated / mh->total_allocated) > 1.5) {
            big_peak = 1;
            num_reports++;
        }

        /* Fragmentation is higher than 1.4 and 10MB ?*/
        if (mh->total_frag > 1.4 && mh->total_frag_bytes > 10<<20) {
            high_frag = 1;
            num_reports++;
        }

        /* External fragmentation is higher than 1.1 and 10MB? */
        if (mh->allocator_frag > 1.1 && mh->allocator_frag_bytes > 10<<20) {
            high_alloc_frag = 1;
            num_reports++;
        }

        /* Allocator rss is higher than 1.1 and 10MB ? */
        if (mh->allocator_rss > 1.1 && mh->allocator_rss_bytes > 10<<20) {
            high_alloc_rss = 1;
            num_reports++;
        }

        /* Non-Allocator rss is higher than 1.1 and 10MB ? */
        if (mh->rss_extra > 1.1 && mh->rss_extra_bytes > 10<<20) {
            high_proc_rss = 1;
            num_reports++;
        }

        /* Clients using more than 200k each average? */
        long numslaves = listLength(server.slaves);
        long numclients = listLength(server.clients)-numslaves;
        if (mh->clients_normal / numclients > (1024*200)) {
            big_client_buf = 1;
            num_reports++;
        }

        /* Slaves using more than 10 MB each? */
        if (numslaves > 0 && mh->clients_slaves > (1024*1024*10)) {
            big_slave_buf = 1;
            num_reports++;
        }

        /* Too many scripts are cached? */
        if (dictSize(evalScriptsDict()) > 1000) {
            many_scripts = 1;
            num_reports++;
        }
    }

    sds s;
    if (num_reports == 0) {
        s = sdsnew(
        "Hi Sam, I can't find any memory issue in your instance. "
        "I can only account for what occurs on this base.\n");
    } else if (empty == 1) {
        s = sdsnew(
        "Hi Sam, this instance is empty or is using very little memory, "
        "my issues detector can't be used in these conditions. "
        "Please, leave for your mission on Earth and fill it with some data. "
        "The new Sam and I will be back to our programming as soon as I "
        "finished rebooting.\n");
    } else {
        s = sdsnew("Sam, I detected a few issues in this Redis instance memory implants:\n\n");
        if (big_peak) {
            s = sdscat(s," * Peak memory: In the past this instance used more than 150% the memory that is currently using. The allocator is normally not able to release memory after a peak, so you can expect to see a big fragmentation ratio, however this is actually harmless and is only due to the memory peak, and if the Redis instance Resident Set Size (RSS) is currently bigger than expected, the memory will be used as soon as you fill the Redis instance with more data. If the memory peak was only occasional and you want to try to reclaim memory, please try the MEMORY PURGE command, otherwise the only other option is to shutdown and restart the instance.\n\n");
        }
        if (high_frag) {
            s = sdscatprintf(s," * High total RSS: This instance has a memory fragmentation and RSS overhead greater than 1.4 (this means that the Resident Set Size of the Redis process is much larger than the sum of the logical allocations Redis performed). This problem is usually due either to a large peak memory (check if there is a peak memory entry above in the report) or may result from a workload that causes the allocator to fragment memory a lot. If the problem is a large peak memory, then there is no issue. Otherwise, make sure you are using the Jemalloc allocator and not the default libc malloc. Note: The currently used allocator is \"%s\".\n\n", ZMALLOC_LIB);
        }
        if (high_alloc_frag) {
            s = sdscatprintf(s," * High allocator fragmentation: This instance has an allocator external fragmentation greater than 1.1. This problem is usually due either to a large peak memory (check if there is a peak memory entry above in the report) or may result from a workload that causes the allocator to fragment memory a lot. You can try enabling 'activedefrag' config option.\n\n");
        }
        if (high_alloc_rss) {
            s = sdscatprintf(s," * High allocator RSS overhead: This instance has an RSS memory overhead is greater than 1.1 (this means that the Resident Set Size of the allocator is much larger than the sum what the allocator actually holds). This problem is usually due to a large peak memory (check if there is a peak memory entry above in the report), you can try the MEMORY PURGE command to reclaim it.\n\n");
        }
        if (high_proc_rss) {
            s = sdscatprintf(s," * High process RSS overhead: This instance has non-allocator RSS memory overhead is greater than 1.1 (this means that the Resident Set Size of the Redis process is much larger than the RSS the allocator holds). This problem may be due to Lua scripts or Modules.\n\n");
        }
        if (big_slave_buf) {
            s = sdscat(s," * Big replica buffers: The replica output buffers in this instance are greater than 10MB for each replica (on average). This likely means that there is some replica instance that is struggling receiving data, either because it is too slow or because of networking issues. As a result, data piles on the master output buffers. Please try to identify what replica is not receiving data correctly and why. You can use the INFO output in order to check the replicas delays and the CLIENT LIST command to check the output buffers of each replica.\n\n");
        }
        if (big_client_buf) {
            s = sdscat(s," * Big client buffers: The clients output buffers in this instance are greater than 200K per client (on average). This may result from different causes, like Pub/Sub clients subscribed to channels bot not receiving data fast enough, so that data piles on the Redis instance output buffer, or clients sending commands with large replies or very large sequences of commands in the same pipeline. Please use the CLIENT LIST command in order to investigate the issue if it causes problems in your instance, or to understand better why certain clients are using a big amount of memory.\n\n");
        }
        if (many_scripts) {
            s = sdscat(s," * Many scripts: There seem to be many cached scripts in this instance (more than 1000). This may be because scripts are generated and `EVAL`ed, instead of being parameterized (with KEYS and ARGV), `SCRIPT LOAD`ed and `EVALSHA`ed. Unless `SCRIPT FLUSH` is called periodically, the scripts' caches may end up consuming most of your memory.\n\n");
        }
        s = sdscat(s,"I'm here to keep you safe, Sam. I want to help you.\n");
    }
    freeMemoryOverheadData(mh);
    return s;
}

/* Set the object LRU/LFU depending on server.maxmemory_policy.
 * The lfu_freq arg is only relevant if policy is MAXMEMORY_FLAG_LFU.
 * The lru_idle and lru_clock args are only relevant if policy
 * is MAXMEMORY_FLAG_LRU.
 * Either or both of them may be <0, in that case, nothing is set. */
int objectSetLRUOrLFU(robj *val, long long lfu_freq, long long lru_idle,
                       long long lru_clock, int lru_multiplier) {
    if (server.maxmemory_policy & MAXMEMORY_FLAG_LFU) {
        if (lfu_freq >= 0) {
            serverAssert(lfu_freq <= 255);
            val->lru = (LFUGetTimeInMinutes()<<8) | lfu_freq;
            return 1;
        }
    } else if (lru_idle >= 0) {
        /* Provided LRU idle time is in seconds. Scale
         * according to the LRU clock resolution this Redis
         * instance was compiled with (normally 1000 ms, so the
         * below statement will expand to lru_idle*1000/1000. */
        lru_idle = lru_idle*lru_multiplier/LRU_CLOCK_RESOLUTION;
        long lru_abs = lru_clock - lru_idle; /* Absolute access time. */
        /* If the LRU field underflows (since lru_clock is a wrapping clock),
         * we need to make it positive again. This be handled by the unwrapping
         * code in estimateObjectIdleTime. I.e. imagine a day when lru_clock
         * wrap arounds (happens once in some 6 months), and becomes a low
         * value, like 10, an lru_idle of 1000 should be near LRU_CLOCK_MAX. */
        if (lru_abs < 0)
            lru_abs += LRU_CLOCK_MAX;
        val->lru = lru_abs;
        return 1;
    }
    return 0;
}

/* ======================= The OBJECT and MEMORY commands =================== */

/* This is a helper function for the OBJECT command. We need to lookup keys
 * without any modification of LRU or other parameters. */
robj *objectCommandLookup(client *c, robj *key) {
    return lookupKeyReadWithFlags(c->db,key,LOOKUP_NOTOUCH|LOOKUP_NONOTIFY);
}

robj *objectCommandLookupOrReply(client *c, robj *key, robj *reply) {
    robj *o = objectCommandLookup(c,key);
    if (!o) addReplyOrErrorObject(c, reply);
    return o;
}

/* Object command allows to inspect the internals of a Redis Object.
 * Usage: OBJECT <refcount|encoding|idletime|freq> <key> */
void objectCommand(client *c) {
    robj *o;

    if (c->argc == 2 && !strcasecmp(c->argv[1]->ptr,"help")) {
        const char *help[] = {
"ENCODING <key>",
"    Return the kind of internal representation used in order to store the value",
"    associated with a <key>.",
"FREQ <key>",
"    Return the access frequency index of the <key>. The returned integer is",
"    proportional to the logarithm of the recent access frequency of the key.",
"IDLETIME <key>",
"    Return the idle time of the <key>, that is the approximated number of",
"    seconds elapsed since the last access to the key.",
"REFCOUNT <key>",
"    Return the number of references of the value associated with the specified",
"    <key>.",
NULL
        };
        addReplyHelp(c, help);
    } else if (!strcasecmp(c->argv[1]->ptr,"refcount") && c->argc == 3) {
        if ((o = objectCommandLookupOrReply(c,c->argv[2],shared.null[c->resp]))
                == NULL) return;
        addReplyLongLong(c,o->refcount);
    } else if (!strcasecmp(c->argv[1]->ptr,"encoding") && c->argc == 3) {
        if ((o = objectCommandLookupOrReply(c,c->argv[2],shared.null[c->resp]))
                == NULL) return;
        addReplyBulkCString(c,strEncoding(o->encoding));
    } else if (!strcasecmp(c->argv[1]->ptr,"idletime") && c->argc == 3) {
        if ((o = objectCommandLookupOrReply(c,c->argv[2],shared.null[c->resp]))
                == NULL) return;
        if (server.maxmemory_policy & MAXMEMORY_FLAG_LFU) {
            addReplyError(c,"An LFU maxmemory policy is selected, idle time not tracked. Please note that when switching between policies at runtime LRU and LFU data will take some time to adjust.");
            return;
        }
        addReplyLongLong(c,estimateObjectIdleTime(o)/1000);
    } else if (!strcasecmp(c->argv[1]->ptr,"freq") && c->argc == 3) {
        if ((o = objectCommandLookupOrReply(c,c->argv[2],shared.null[c->resp]))
                == NULL) return;
        if (!(server.maxmemory_policy & MAXMEMORY_FLAG_LFU)) {
            addReplyError(c,"An LFU maxmemory policy is not selected, access frequency not tracked. Please note that when switching between policies at runtime LRU and LFU data will take some time to adjust.");
            return;
        }
        /* LFUDecrAndReturn should be called
         * in case of the key has not been accessed for a long time,
         * because we update the access time only
         * when the key is read or overwritten. */
        addReplyLongLong(c,LFUDecrAndReturn(o));
    } else {
        addReplySubcommandSyntaxError(c);
    }
}

/* The memory command will eventually be a complete interface for the
 * memory introspection capabilities of Redis.
 *
 * Usage: MEMORY usage <key> */
void memoryCommand(client *c) {
    if (!strcasecmp(c->argv[1]->ptr,"help") && c->argc == 2) {
        const char *help[] = {
"DOCTOR",
"    Return memory problems reports.",
"MALLOC-STATS",
"    Return internal statistics report from the memory allocator.",
"PURGE",
"    Attempt to purge dirty pages for reclamation by the allocator.",
"STATS",
"    Return information about the memory usage of the server.",
"USAGE <key> [SAMPLES <count>]",
"    Return memory in bytes used by <key> and its value. Nested values are",
"    sampled up to <count> times (default: 5, 0 means sample all).",
NULL
        };
        addReplyHelp(c, help);
    } else if (!strcasecmp(c->argv[1]->ptr,"usage") && c->argc >= 3) {
        dictEntry *de;
        long long samples = OBJ_COMPUTE_SIZE_DEF_SAMPLES;
        for (int j = 3; j < c->argc; j++) {
            if (!strcasecmp(c->argv[j]->ptr,"samples") &&
                j+1 < c->argc)
            {
                if (getLongLongFromObjectOrReply(c,c->argv[j+1],&samples,NULL)
                     == C_ERR) return;
                if (samples < 0) {
                    addReplyErrorObject(c,shared.syntaxerr);
                    return;
                }
                if (samples == 0) samples = LLONG_MAX;
                j++; /* skip option argument. */
            } else {
                addReplyErrorObject(c,shared.syntaxerr);
                return;
            }
        }
        if ((de = dictFind(c->db->dict,c->argv[2]->ptr)) == NULL) {
            addReplyNull(c);
            return;
        }
        size_t usage = objectComputeSize(c->argv[2],dictGetVal(de),samples,c->db->id);
        usage += sdsZmallocSize(dictGetKey(de));
        usage += dictEntryMemUsage();
        usage += dictMetadataSize(c->db->dict);
        addReplyLongLong(c,usage);
    } else if (!strcasecmp(c->argv[1]->ptr,"stats") && c->argc == 2) {
        struct redisMemOverhead *mh = getMemoryOverheadData();

        addReplyMapLen(c,27+mh->num_dbs);

        addReplyBulkCString(c,"peak.allocated");
        addReplyLongLong(c,mh->peak_allocated);

        addReplyBulkCString(c,"total.allocated");
        addReplyLongLong(c,mh->total_allocated);

        addReplyBulkCString(c,"startup.allocated");
        addReplyLongLong(c,mh->startup_allocated);

        addReplyBulkCString(c,"replication.backlog");
        addReplyLongLong(c,mh->repl_backlog);

        addReplyBulkCString(c,"clients.slaves");
        addReplyLongLong(c,mh->clients_slaves);

        addReplyBulkCString(c,"clients.normal");
        addReplyLongLong(c,mh->clients_normal);

        addReplyBulkCString(c,"cluster.links");
        addReplyLongLong(c,mh->cluster_links);

        addReplyBulkCString(c,"aof.buffer");
        addReplyLongLong(c,mh->aof_buffer);

        addReplyBulkCString(c,"lua.caches");
        addReplyLongLong(c,mh->lua_caches);

        addReplyBulkCString(c,"functions.caches");
        addReplyLongLong(c,mh->functions_caches);

        for (size_t j = 0; j < mh->num_dbs; j++) {
            char dbname[32];
            snprintf(dbname,sizeof(dbname),"db.%zd",mh->db[j].dbid);
            addReplyBulkCString(c,dbname);
            addReplyMapLen(c,3);

            addReplyBulkCString(c,"overhead.hashtable.main");
            addReplyLongLong(c,mh->db[j].overhead_ht_main);

            addReplyBulkCString(c,"overhead.hashtable.expires");
            addReplyLongLong(c,mh->db[j].overhead_ht_expires);

            addReplyBulkCString(c,"overhead.hashtable.slot-to-keys");
            addReplyLongLong(c,mh->db[j].overhead_ht_slot_to_keys);
        }


        addReplyBulkCString(c,"overhead.total");
        addReplyLongLong(c,mh->overhead_total);

        addReplyBulkCString(c,"keys.count");
        addReplyLongLong(c,mh->total_keys);

        addReplyBulkCString(c,"keys.bytes-per-key");
        addReplyLongLong(c,mh->bytes_per_key);

        addReplyBulkCString(c,"dataset.bytes");
        addReplyLongLong(c,mh->dataset);

        addReplyBulkCString(c,"dataset.percentage");
        addReplyDouble(c,mh->dataset_perc);

        addReplyBulkCString(c,"peak.percentage");
        addReplyDouble(c,mh->peak_perc);

        addReplyBulkCString(c,"allocator.allocated");
        addReplyLongLong(c,server.cron_malloc_stats.allocator_allocated);

        addReplyBulkCString(c,"allocator.active");
        addReplyLongLong(c,server.cron_malloc_stats.allocator_active);

        addReplyBulkCString(c,"allocator.resident");
        addReplyLongLong(c,server.cron_malloc_stats.allocator_resident);

        addReplyBulkCString(c,"allocator-fragmentation.ratio");
        addReplyDouble(c,mh->allocator_frag);

        addReplyBulkCString(c,"allocator-fragmentation.bytes");
        addReplyLongLong(c,mh->allocator_frag_bytes);

        addReplyBulkCString(c,"allocator-rss.ratio");
        addReplyDouble(c,mh->allocator_rss);

        addReplyBulkCString(c,"allocator-rss.bytes");
        addReplyLongLong(c,mh->allocator_rss_bytes);

        addReplyBulkCString(c,"rss-overhead.ratio");
        addReplyDouble(c,mh->rss_extra);

        addReplyBulkCString(c,"rss-overhead.bytes");
        addReplyLongLong(c,mh->rss_extra_bytes);

        addReplyBulkCString(c,"fragmentation"); /* this is the total RSS overhead, including fragmentation */
        addReplyDouble(c,mh->total_frag); /* it is kept here for backwards compatibility */

        addReplyBulkCString(c,"fragmentation.bytes");
        addReplyLongLong(c,mh->total_frag_bytes);

        freeMemoryOverheadData(mh);
    } else if (!strcasecmp(c->argv[1]->ptr,"malloc-stats") && c->argc == 2) {
#if defined(USE_JEMALLOC)
        sds info = sdsempty();
        je_malloc_stats_print(inputCatSds, &info, NULL);
        addReplyVerbatim(c,info,sdslen(info),"txt");
        sdsfree(info);
#else
        addReplyBulkCString(c,"Stats not supported for the current allocator");
#endif
    } else if (!strcasecmp(c->argv[1]->ptr,"doctor") && c->argc == 2) {
        sds report = getMemoryDoctorReport();
        addReplyVerbatim(c,report,sdslen(report),"txt");
        sdsfree(report);
    } else if (!strcasecmp(c->argv[1]->ptr,"purge") && c->argc == 2) {
        if (jemalloc_purge() == 0)
            addReply(c, shared.ok);
        else
            addReplyError(c, "Error purging dirty pages");
    } else {
        addReplySubcommandSyntaxError(c);
    }
}