Re: [tarantool-patches] Re: [PATCH v2 1/1] box: create bigrefs for tuples

[Vladislav Shpilevoy <v.shpilevoy@tarantool.org>]

Sorry, Vladimir. Please, disregard it. I have found and fixed a crash.
Looks like Mergen must implement unit tests.

Test bigrefs via Lua is not possible because of its memory limitation.

Mergen, please, implement unit tests on C for your patch and for my
follow up. You must cover each branch in each new function.


On 04/06/2018 23:57, Vladislav Shpilevoy wrote:
> Thanks for the patch, Mergen! Please look at my 5 comments.
> 
> Vova, please, take a look on the patch. I have pasted it at the end
> of the letter.
> 
> On 04/06/2018 17:21, Imeev Mergen wrote:
>>
>>
>> On 06/04/2018 02:21 PM, Vladislav Shpilevoy wrote:
>>> Hello. Thanks for the patch! It is almost perfect! See 6 comments
>>> below.
>>>
>>> On 01/06/2018 18:41, imeevma@tarantool.org wrote:
>>>> Due to limitation of reference counters for tuple being only
>>>> 65535 it was possible to reach this limitation. This patch
>>>> increases capacity of reference counters to 4 billions.
>>>>
>>>> Closes #3224
>>>> ---
>>>> Branch: https://github.com/tarantool/tarantool/tree/imeevma/gh-3224-tuple-bigrefs
>>>> Issue: https://github.com/tarantool/tarantool/issues/3224
>>>>
>>
>> commit 7b7965f6c5462142a607d9db542d698fc94fbbbe
>> Author: Mergen Imeev <imeevma@gmail.com>
>> Date:   Mon May 28 19:17:51 2018 +0300
>>
>>      box: create bigrefs for tuples
>>
>>      Due to limitation of reference counters for tuple being only
>>      65535 it was possible to reach this limitation. This patch
>>      increases capacity of reference counters to 4 billions.
>>
>>      Closes #3224
>>
>> diff --git a/src/box/tuple.c b/src/box/tuple.c
>> index 014f374..6e63433 100644
>> --- a/src/box/tuple.c
>> +++ b/src/box/tuple.c
>> @@ -48,6 +48,26 @@ enum {
>>       OBJSIZE_MIN = 16,
>>   };
>>
>> +/**
>> + * Container for big reference counters. Contains array of big
>> + * reference counters, size of this array and number of non-zero
>> + * big reference counters. When reference counter of tuple becomes
>> + * more than 32767, field refs of this tuple becomes index of big
>> + * reference counter in big reference counter array and field
>> + * is_bigref is set true. The moment big reference becomes equal
>> + * 32767 it is set to 0, refs of the tuple becomes 32767 and
>> + * is_bigref becomes false. Big reference counter can be equal to
>> + * 0 or be more than 32767.
>> + */
>> +struct bigref_list {
>> +    /** Array of big reference counters */
>> +    uint32_t *refs;
>> +    /** Number of non-zero elements in the array */
>> +    uint16_t size;
>> +    /** Capacity of the array */
>> +    uint16_t capacity;
>> +};
> 
> 1. Instead of
> 
>      struct name {
>          ...
>      };
>      static struct name name;
> 
> you can do this
> 
>      static struct name {
>          ...
>      } name;
> 
>> +
>>   static const double ALLOC_FACTOR = 1.05;
>>
>>   /**
>> @@ -151,6 +177,15 @@ tuple_validate_raw(struct tuple_format *format, const char *tuple)
>>       return 0;
>>   }
>>
>> +/** Initialize big references container. */
>> +static inline void
>> +bigref_list_create()
>> +{
>> +    bigref_list.size = 0;
>> +    bigref_list.refs = NULL;
>> +    bigref_list.capacity = 0;
> 
> 2. Memset is faster than per-member resetting. We with
> Vladimir Davydov have benched it.
> 
>> +/**
>> + * Return index for new big reference counter and allocate memory
>> + * if needed.
>> + * @retval index for new big reference counter.
>> + */
>> +static inline uint16_t
>> +tuple_bigref_retrieve()
>> +{
>> +    if (bigref_list.size < bigref_list.capacity) {
>> +        uint16_t vacant_index = 0;
>> +        while (bigref_list.refs[vacant_index] != 0)
>> +            ++vacant_index;
>> +        return vacant_index;
>> +    }
>> +    /* Extend the array. */
>> +    uint16_t capacity = bigref_list.capacity;
>> +    if (capacity == 0) {
>> +        capacity = TUPLE_BIGREF_MIN_CAPACITY;
>> +    } else {
>> +        capacity *= TUPLE_BIGREF_FACTOR;
>> +        if (capacity >= TUPLE_BIGREF_MAX_CAPACITY)
> 
> 3. By such check you have limited the capacity with 16384 bigrefs instead of
> 32k. Capacity here is always a power of 2. TUPLE_BIGREF_MAX_CAPACITY is
> 2^15. So here after 2^14 you get overflow. 2^14 = 16384. I have fixed it on
> the branch.
> 
>> +            panic("Too many big references");
>> +    }
>> +    uint32_t *refs = (uint32_t *) realloc(bigref_list.refs, capacity *
>> +                          sizeof(*bigref_list.refs));
>> +    if (refs == NULL) {
>> +        panic("failed to reallocate %zu bytes: Cannot allocate"\
>> +              " memory.", capacity * sizeof(*bigref_list.refs));
>> +    }
>> +    bigref_list.refs = refs;
>> +    memset(bigref_list.refs + bigref_list.capacity, 0, capacity -
>> +           bigref_list.capacity);
>> +    bigref_list.capacity = capacity;
>> +    return bigref_list.size++;
>> +}
>> +
>> +/**
>> + * Try to decrease allocated memory if it is possible. Free memory
>> + * when size == 0.
>> + */
>> +static inline void
>> +bigref_list_compact()
>> +{
>> +    if (bigref_list.size == 0) {
>> +        bigref_list_destroy();
>> +        return;
>> +    }
>> +    if (bigref_list.capacity == TUPLE_BIGREF_MIN_CAPACITY ||
>> +        bigref_list.size > bigref_list.capacity / TUPLE_BIGREF_FACTOR)
>> +        return;
>> +    uint16_t capacity = bigref_list.capacity;
>> +    while (bigref_list.refs[capacity - 1] == 0)
>> +        capacity--;
>> +    if (capacity < TUPLE_BIGREF_MIN_CAPACITY)
>> +        capacity = TUPLE_BIGREF_MIN_CAPACITY;
>> +    if (capacity > bigref_list.capacity / TUPLE_BIGREF_FACTOR)
>> +        return;
>> +    /* Round up capacity to the next highest power of 2*/
>> +    capacity--;
>> +    capacity |= capacity >> 1;
>> +    capacity |= capacity >> 2;
>> +    capacity |= capacity >> 4;
>> +    capacity |= capacity >> 8;
>> +    capacity |= capacity >> 16;
> 
> 4. This is because blind copy and paste is bad. The algorithm implementation
> I provided to you was for 32 bit unsigned integers, but here you have 16 bits
> only, so capacity >> 16 is always 0.
> 
>> +    capacity++;
>> +    uint32_t *refs = (uint32_t *) realloc(bigref_list.refs, capacity *
>> +                          sizeof(*bigref_list.refs));
>> +    if (refs == NULL)
>> +        panic("failed to reallocate %zu bytes: Cannot allocate"\
>> +              " memory.", capacity * sizeof(*bigref_list.refs));
>> +    bigref_list.refs = refs;
>> +    bigref_list.capacity = capacity;
>> +}
>> +
> 
> 5. I have removed tuple_bless == NULL checks from all the code.
> 
> Here the patch:
> 
> ============================================================================
> 
> commit 9d82fa9f9ae24c7dc91cf9dd7a416ec533fb8147
> Author: Mergen Imeev <imeevma@gmail.com>
> Date:   Mon May 28 19:17:51 2018 +0300
> 
>      box: create bigrefs for tuples
>      Due to limitation of reference counters for tuple being only
>      65535 it was possible to reach this limitation. This patch
>      increases capacity of reference counters to 4 billions.
>      Closes #3224
> 
> diff --git a/src/box/box.cc b/src/box/box.cc
> index c728a4c53..42578613d 100644
> --- a/src/box/box.cc
> +++ b/src/box/box.cc
> @@ -174,20 +174,22 @@ process_rw(struct request *request, struct space *space, struct tuple **result)
>           txn_rollback_stmt();
>           return -1;
>       }
> +    if (result == NULL)
> +        return txn_commit_stmt(txn, request);
> +    *result = tuple;
> +    if (tuple == NULL)
> +        return txn_commit_stmt(txn, request);
>       /*
>        * Pin the tuple locally before the commit,
>        * otherwise it may go away during yield in
>        * when WAL is written in autocommit mode.
>        */
> -    TupleRefNil ref(tuple);
> -    if (txn_commit_stmt(txn, request) != 0)
> -        return -1;
> -    if (result != NULL) {
> -        if (tuple != NULL && tuple_bless(tuple) == NULL)
> -            return -1;
> -        *result = tuple;
> -    }
> -    return 0;
> +    tuple_ref(tuple);
> +    int rc = txn_commit_stmt(txn, request);
> +    if (rc == 0)
> +        tuple_bless(tuple);
> +    tuple_unref(tuple);
> +    return rc;
>   }
> 
>   void
> diff --git a/src/box/errcode.h b/src/box/errcode.h
> index a0759f8f4..e009524ad 100644
> --- a/src/box/errcode.h
> +++ b/src/box/errcode.h
> @@ -138,7 +138,7 @@ struct errcode_record {
>       /* 83 */_(ER_ROLE_EXISTS,        "Role '%s' already exists") \
>       /* 84 */_(ER_CREATE_ROLE,        "Failed to create role '%s': %s") \
>       /* 85 */_(ER_INDEX_EXISTS,        "Index '%s' already exists") \
> -    /* 86 */_(ER_TUPLE_REF_OVERFLOW,    "Tuple reference counter overflow") \
> +    /* 86 */_(ER_UNUSED6,            "") \
>       /* 87 */_(ER_ROLE_LOOP,            "Granting role '%s' to role '%s' would create a loop") \
>       /* 88 */_(ER_GRANT,            "Incorrect grant arguments: %s") \
>       /* 89 */_(ER_PRIV_GRANTED,        "User '%s' already has %s access on %s '%s'") \
> diff --git a/src/box/index.cc b/src/box/index.cc
> index 3c62ec1cc..f992bc94c 100644
> --- a/src/box/index.cc
> +++ b/src/box/index.cc
> @@ -220,8 +220,8 @@ box_index_random(uint32_t space_id, uint32_t index_id, uint32_t rnd,
>       /* No tx management, random() is for approximation anyway. */
>       if (index_random(index, rnd, result) != 0)
>           return -1;
> -    if (*result != NULL && tuple_bless(*result) == NULL)
> -        return -1;
> +    if (*result != NULL)
> +        tuple_bless(*result);
>       return 0;
>   }
> 
> @@ -253,8 +253,8 @@ box_index_get(uint32_t space_id, uint32_t index_id, const char *key,
>       txn_commit_ro_stmt(txn);
>       /* Count statistics. */
>       rmean_collect(rmean_box, IPROTO_SELECT, 1);
> -    if (*result != NULL && tuple_bless(*result) == NULL)
> -        return -1;
> +    if (*result != NULL)
> +        tuple_bless(*result);
>       return 0;
>   }
> 
> @@ -285,8 +285,8 @@ box_index_min(uint32_t space_id, uint32_t index_id, const char *key,
>           return -1;
>       }
>       txn_commit_ro_stmt(txn);
> -    if (*result != NULL && tuple_bless(*result) == NULL)
> -        return -1;
> +    if (*result != NULL)
> +        tuple_bless(*result);
>       return 0;
>   }
> 
> @@ -317,8 +317,8 @@ box_index_max(uint32_t space_id, uint32_t index_id, const char *key,
>           return -1;
>       }
>       txn_commit_ro_stmt(txn);
> -    if (*result != NULL && tuple_bless(*result) == NULL)
> -        return -1;
> +    if (*result != NULL)
> +        tuple_bless(*result);
>       return 0;
>   }
> 
> @@ -397,8 +397,8 @@ box_iterator_next(box_iterator_t *itr, box_tuple_t **result)
>       assert(result != NULL);
>       if (iterator_next(itr, result) != 0)
>           return -1;
> -    if (*result != NULL && tuple_bless(*result) == NULL)
> -        return -1;
> +    if (*result != NULL)
> +        tuple_bless(*result);
>       return 0;
>   }
> 
> diff --git a/src/box/lua/tuple.c b/src/box/lua/tuple.c
> index 80573313d..22fe69611 100644
> --- a/src/box/lua/tuple.c
> +++ b/src/box/lua/tuple.c
> @@ -496,10 +496,7 @@ luaT_pushtuple(struct lua_State *L, box_tuple_t *tuple)
>           luaL_pushcdata(L, CTID_CONST_STRUCT_TUPLE_REF);
>       *ptr = tuple;
>       /* The order is important - first reference tuple, next set gc */
> -    if (box_tuple_ref(tuple) != 0) {
> -        luaT_error(L);
> -        return;
> -    }
> +    box_tuple_ref(tuple);
>       lua_pushcfunction(L, lbox_tuple_gc);
>       luaL_setcdatagc(L, -2);
>   }
> diff --git a/src/box/port.c b/src/box/port.c
> index 03f6be79d..9b6b8580c 100644
> --- a/src/box/port.c
> +++ b/src/box/port.c
> @@ -45,8 +45,7 @@ port_tuple_add(struct port *base, struct tuple *tuple)
>       struct port_tuple *port = port_tuple(base);
>       struct port_tuple_entry *e;
>       if (port->size == 0) {
> -        if (tuple_ref(tuple) != 0)
> -            return -1;
> +        tuple_ref(tuple);
>           e = &port->first_entry;
>           port->first = port->last = e;
>       } else {
> @@ -55,10 +54,7 @@ port_tuple_add(struct port *base, struct tuple *tuple)
>               diag_set(OutOfMemory, sizeof(*e), "mempool_alloc", "e");
>               return -1;
>           }
> -        if (tuple_ref(tuple) != 0) {
> -            mempool_free(&port_tuple_entry_pool, e);
> -            return -1;
> -        }
> +        tuple_ref(tuple);
>           port->last->next = e;
>           port->last = e;
>       }
> diff --git a/src/box/tuple.c b/src/box/tuple.c
> index 014f37406..5fc1c1283 100644
> --- a/src/box/tuple.c
> +++ b/src/box/tuple.c
> @@ -48,6 +48,26 @@ enum {
>       OBJSIZE_MIN = 16,
>   };
> 
> +/**
> + * Container for big reference counters. Contains array of big
> + * reference counters, size of this array and number of non-zero
> + * big reference counters. When reference counter of tuple becomes
> + * more than 32767, field refs of this tuple becomes index of big
> + * reference counter in big reference counter array and field
> + * is_bigref is set true. The moment big reference becomes equal
> + * 32767 it is set to 0, refs of the tuple becomes 32767 and
> + * is_bigref becomes false. Big reference counter can be equal to
> + * 0 or be more than 32767.
> + */
> +static struct bigref_list {
> +    /** Array of big reference counters. */
> +    uint32_t *refs;
> +    /** Number of non-zero elements in the array. */
> +    uint16_t size;
> +    /** Capacity of the array. */
> +    uint16_t capacity;
> +} bigref_list;
> +
>   static const double ALLOC_FACTOR = 1.05;
> 
>   /**
> @@ -151,6 +171,13 @@ tuple_validate_raw(struct tuple_format *format, const char *tuple)
>       return 0;
>   }
> 
> +/** Initialize big references container. */
> +static inline void
> +bigref_list_create()
> +{
> +    memset(&bigref_list, 0, sizeof(bigref_list));
> +}
> +
>   /**
>    * Incremented on every snapshot and is used to distinguish tuples
>    * which were created after start of a snapshot (these tuples can
> @@ -211,6 +238,8 @@ tuple_init(field_name_hash_f hash)
> 
>       box_tuple_last = NULL;
> 
> +    bigref_list_create();
> +
>       if (coll_id_cache_init() != 0)
>           return -1;
> 
> @@ -244,6 +273,131 @@ tuple_arena_create(struct slab_arena *arena, struct quota *quota,
>       }
>   }
> 
> +enum {
> +    BIGREF_FACTOR = 2,
> +    BIGREF_MAX = UINT32_MAX,
> +    BIGREF_MIN_CAPACITY = 16,
> +    /**
> +     * Only 15 bits are available for bigref list index in
> +     * struct tuple.
> +     */
> +    BIGREF_MAX_CAPACITY = UINT16_MAX >> 1
> +};
> +
> +/** Destroy big references and free memory that was allocated. */
> +static inline void
> +bigref_list_destroy()
> +{
> +    free(bigref_list.refs);
> +    bigref_list_create();
> +}
> +
> +/**
> + * Return index for new big reference counter and allocate memory
> + * if needed.
> + * @retval index for new big reference counter.
> + */
> +static inline uint16_t
> +bigref_list_new_index()
> +{
> +    if (bigref_list.size < bigref_list.capacity) {
> +        uint16_t vacant_index = 0;
> +        while (bigref_list.refs[vacant_index] != 0)
> +            ++vacant_index;
> +        return vacant_index;
> +    }
> +    /* Extend the array. */
> +    uint16_t capacity = bigref_list.capacity;
> +    if (capacity == 0)
> +        capacity = BIGREF_MIN_CAPACITY;
> +    else if (capacity < BIGREF_MAX_CAPACITY)
> +        capacity = MIN(capacity * BIGREF_FACTOR, BIGREF_MAX_CAPACITY);
> +    else
> +        panic("Too many big references");
> +    uint32_t *refs = (uint32_t *) realloc(bigref_list.refs, capacity *
> +                          sizeof(*bigref_list.refs));
> +    if (refs == NULL) {
> +        panic("failed to reallocate %zu bytes: Cannot allocate "\
> +              "memory.", capacity * sizeof(*bigref_list.refs));
> +    }
> +    bigref_list.refs = refs;
> +    memset(bigref_list.refs + bigref_list.capacity, 0, capacity -
> +           bigref_list.capacity);
> +    bigref_list.capacity = capacity;
> +    return bigref_list.size++;
> +}
> +
> +void
> +tuple_ref_slow(struct tuple *tuple)
> +{
> +    assert(tuple->is_bigref || tuple->refs == TUPLE_REF_MAX);
> +    if (! tuple->is_bigref) {
> +        tuple->ref_index = bigref_list_new_index();
> +        tuple->is_bigref = true;
> +        bigref_list.refs[tuple->ref_index] = TUPLE_REF_MAX;
> +    } else if (bigref_list.refs[tuple->ref_index] == BIGREF_MAX) {
> +        panic("Tuple big reference counter overflow");
> +    }
> +    bigref_list.refs[tuple->ref_index]++;
> +}
> +
> +/**
> + * Try to decrease allocated memory if it is possible. Free memory
> + * when size == 0.
> + */
> +static inline void
> +bigref_list_delete_index(uint16_t index)
> +{
> +    bigref_list.refs[index] = 0;
> +    if (--bigref_list.size == 0) {
> +        bigref_list_destroy();
> +        return;
> +    }
> +    if (bigref_list.capacity == BIGREF_MIN_CAPACITY ||
> +        bigref_list.size > bigref_list.capacity / BIGREF_FACTOR)
> +        return;
> +
> +    uint16_t top_index = bigref_list.capacity - 1;
> +    while (bigref_list.refs[top_index] == 0)
> +        top_index--;
> +
> +    uint16_t needed_capacity = top_index + 1;
> +    if (needed_capacity < BIGREF_MIN_CAPACITY)
> +        needed_capacity = BIGREF_MIN_CAPACITY;
> +    if (needed_capacity > bigref_list.capacity / BIGREF_FACTOR)
> +        return;
> +    /* Round up capacity to the next highest power of 2. */
> +    assert(sizeof(needed_capacity) == sizeof(uint16_t));
> +    needed_capacity--;
> +    needed_capacity |= needed_capacity >> 1;
> +    needed_capacity |= needed_capacity >> 2;
> +    needed_capacity |= needed_capacity >> 4;
> +    needed_capacity |= needed_capacity >> 8;
> +    assert(needed_capacity < UINT16_MAX);
> +    needed_capacity++;
> +    uint32_t *refs =
> +        (uint32_t *) realloc(bigref_list.refs, needed_capacity *
> +                     sizeof(*bigref_list.refs));
> +    if (refs == NULL) {
> +        panic("failed to reallocate %zu bytes: Cannot allocate "\
> +              "memory.", needed_capacity * sizeof(*bigref_list.refs));
> +    }
> +    bigref_list.refs = refs;
> +    bigref_list.capacity = needed_capacity;
> +}
> +
> +void
> +tuple_unref_slow(struct tuple *tuple)
> +{
> +    assert(tuple->is_bigref &&
> +           bigref_list.refs[tuple->ref_index] > TUPLE_REF_MAX);
> +    if(--bigref_list.refs[tuple->ref_index] == TUPLE_REF_MAX) {
> +        bigref_list_delete_index(tuple->ref_index);
> +        tuple->ref_index = TUPLE_REF_MAX;
> +        tuple->is_bigref = false;
> +    }
> +}
> +
>   void
>   tuple_arena_destroy(struct slab_arena *arena)
>   {
> @@ -265,6 +419,8 @@ tuple_free(void)
>       tuple_format_free();
> 
>       coll_id_cache_destroy();
> +
> +    bigref_list_destroy();
>   }
> 
>   box_tuple_format_t *
> @@ -288,7 +444,8 @@ int
>   box_tuple_ref(box_tuple_t *tuple)
>   {
>       assert(tuple != NULL);
> -    return tuple_ref(tuple);
> +    tuple_ref(tuple);
> +    return 0;
>   }
> 
>   void
> @@ -357,10 +514,7 @@ box_tuple_iterator(box_tuple_t *tuple)
>                "mempool", "new slab");
>           return NULL;
>       }
> -    if (tuple_ref(tuple) != 0) {
> -        mempool_free(&tuple_iterator_pool, it);
> -        return NULL;
> -    }
> +    tuple_ref(tuple);
>       tuple_rewind(it, tuple);
>       return it;
>   }
> @@ -451,7 +605,6 @@ box_tuple_new(box_tuple_format_t *format, const char *data, const char *end)
>       struct tuple *ret = tuple_new(format, data, end);
>       if (ret == NULL)
>           return NULL;
> -    /* Can't fail on zero refs. */
>       return tuple_bless(ret);
>   }
> 
> diff --git a/src/box/tuple.h b/src/box/tuple.h
> index e2384dda0..14dbd4094 100644
> --- a/src/box/tuple.h
> +++ b/src/box/tuple.h
> @@ -105,8 +105,7 @@ typedef struct tuple box_tuple_t;
>    * tuple will leak.
>    *
>    * \param tuple a tuple
> - * \retval -1 on error (check box_error_last())
> - * \retval 0 on success
> + * \retval 0 always
>    * \sa box_tuple_unref()
>    */
>   int
> @@ -269,8 +268,7 @@ box_tuple_next(box_tuple_iterator_t *it);
>    * Use box_tuple_format_default() to create space-independent tuple.
>    * \param data tuple data in MsgPack Array format ([field1, field2, ...]).
>    * \param end the end of \a data
> - * \retval NULL on out of memory
> - * \retval tuple otherwise
> + * \retval tuple
>    * \pre data, end is valid MsgPack Array
>    * \sa \code box.tuple.new(data) \endcode
>    */
> @@ -307,9 +305,17 @@ box_tuple_upsert(const box_tuple_t *tuple, const char *expr, const
>    */
>   struct PACKED tuple
>   {
> -    /** reference counter */
> -    uint16_t refs;
> -    /** format identifier */
> +    union {
> +        /** Reference counter. */
> +        uint16_t refs;
> +        struct {
> +            /** Index of big reference counter. */
> +            uint16_t ref_index : 15;
> +            /** Big reference flag. */
> +            bool is_bigref : 1;
> +        };
> +    };
> +    /** Format identifier. */
>       uint16_t format_id;
>       /**
>        * Length of the MessagePack data in raw part of the
> @@ -774,25 +780,35 @@ tuple_field_uuid(const struct tuple *tuple, int fieldno,
>       return 0;
>   }
> 
> -enum { TUPLE_REF_MAX = UINT16_MAX };
> +enum { TUPLE_REF_MAX = UINT16_MAX >> 1 };
> +
> +/**
> + * Increase tuple big reference counter.
> + * @param tuple Tuple to reference.
> + */
> +void
> +tuple_ref_slow(struct tuple *tuple);
> 
>   /**
>    * Increment tuple reference counter.
>    * @param tuple Tuple to reference.
> - * @retval  0 Success.
> - * @retval -1 Too many refs error.
>    */
> -static inline int
> +static inline void
>   tuple_ref(struct tuple *tuple)
>   {
> -    if (tuple->refs + 1 > TUPLE_REF_MAX) {
> -        diag_set(ClientError, ER_TUPLE_REF_OVERFLOW);
> -        return -1;
> -    }
> -    tuple->refs++;
> -    return 0;
> +    if (unlikely(tuple->refs >= TUPLE_REF_MAX))
> +        tuple_ref_slow(tuple);
> +    else
> +        tuple->refs++;
>   }
> 
> +/**
> + * Decrease tuple big reference counter.
> + * @param tuple Tuple to reference.
> + */
> +void
> +tuple_unref_slow(struct tuple *tuple);
> +
>   /**
>    * Decrement tuple reference counter. If it has reached zero, free the tuple.
>    *
> @@ -802,10 +818,9 @@ static inline void
>   tuple_unref(struct tuple *tuple)
>   {
>       assert(tuple->refs - 1 >= 0);
> -
> -    tuple->refs--;
> -
> -    if (tuple->refs == 0)
> +    if (unlikely(tuple->is_bigref))
> +        tuple_unref_slow(tuple);
> +    else if (--tuple->refs == 0)
>           tuple_delete(tuple);
>   }
> 
> @@ -813,25 +828,18 @@ extern struct tuple *box_tuple_last;
> 
>   /**
>    * Convert internal `struct tuple` to public `box_tuple_t`.
> - * \retval tuple on success
> - * \retval NULL on error, check diag
> + * \retval tuple
>    * \post \a tuple ref counted until the next call.
> - * \post tuple_ref() doesn't fail at least once
>    * \sa tuple_ref
>    */
>   static inline box_tuple_t *
>   tuple_bless(struct tuple *tuple)
>   {
>       assert(tuple != NULL);
> -    /* Ensure tuple can be referenced at least once after return */
> -    if (tuple->refs + 2 > TUPLE_REF_MAX) {
> -        diag_set(ClientError, ER_TUPLE_REF_OVERFLOW);
> -        return NULL;
> -    }
> -    tuple->refs++;
> +    tuple_ref(tuple);
>       /* Remove previous tuple */
>       if (likely(box_tuple_last != NULL))
> -        tuple_unref(box_tuple_last); /* do not throw */
> +        tuple_unref(box_tuple_last);
>       /* Remember current tuple */
>       box_tuple_last = tuple;
>       return tuple;
> @@ -849,41 +857,6 @@ tuple_to_buf(const struct tuple *tuple, char *buf, size_t size);
>   #include "tuple_update.h"
>   #include "errinj.h"
> 
> -/**
> - * \copydoc tuple_ref()
> - * \throws if overflow detected.
> - */
> -static inline void
> -tuple_ref_xc(struct tuple *tuple)
> -{
> -    if (tuple_ref(tuple))
> -        diag_raise();
> -}
> -
> -/**
> - * \copydoc tuple_bless
> - * \throw ER_TUPLE_REF_OVERFLOW
> - */
> -static inline box_tuple_t *
> -tuple_bless_xc(struct tuple *tuple)
> -{
> -    box_tuple_t *blessed = tuple_bless(tuple);
> -    if (blessed == NULL)
> -        diag_raise();
> -    return blessed;
> -}
> -
> -/** Make tuple references exception-friendly in absence of @finally. */
> -struct TupleRefNil {
> -    struct tuple *tuple;
> -    TupleRefNil (struct tuple *arg) :tuple(arg)
> -    { if (tuple) tuple_ref_xc(tuple); }
> -    ~TupleRefNil() { if (tuple) tuple_unref(tuple); }
> -
> -    TupleRefNil(const TupleRefNil&) = delete;
> -    void operator=(const TupleRefNil&) = delete;
> -};
> -
>   /* @copydoc tuple_field_with_type() */
>   static inline const char *
>   tuple_field_with_type_xc(const struct tuple *tuple, uint32_t fieldno,
> diff --git a/src/box/vinyl.c b/src/box/vinyl.c
> index f0d26874e..dc0d02054 100644
> --- a/src/box/vinyl.c
> +++ b/src/box/vinyl.c
> @@ -3822,7 +3822,6 @@ vinyl_iterator_primary_next(struct iterator *base, struct tuple **ret)
>       assert(base->next = vinyl_iterator_primary_next);
>       struct vinyl_iterator *it = (struct vinyl_iterator *)base;
>       assert(it->lsm->index_id == 0);
> -    struct tuple *tuple;
> 
>       if (it->tx == NULL) {
>           diag_set(ClientError, ER_CURSOR_NO_TRANSACTION);
> @@ -3833,18 +3832,15 @@ vinyl_iterator_primary_next(struct iterator *base, struct tuple **ret)
>           goto fail;
>       }
> 
> -    if (vy_read_iterator_next(&it->iterator, &tuple) != 0)
> +    if (vy_read_iterator_next(&it->iterator, ret) != 0)
>           goto fail;
> -
> -    if (tuple == NULL) {
> +    if (*ret == NULL) {
>           /* EOF. Close the iterator immediately. */
>           vinyl_iterator_close(it);
> -        *ret = NULL;
> -        return 0;
> +    } else {
> +        tuple_bless(*ret);
>       }
> -    *ret = tuple_bless(tuple);
> -    if (*ret != NULL)
> -        return 0;
> +    return 0;
>   fail:
>       vinyl_iterator_close(it);
>       return -1;
> @@ -3890,11 +3886,10 @@ next:
>        * Note, there's no need in vy_tx_track() as the
>        * tuple is already tracked in the secondary index.
>        */
> -    struct tuple *full_tuple;
>       if (vy_point_lookup(it->lsm->pk, it->tx, vy_tx_read_view(it->tx),
> -                tuple, &full_tuple) != 0)
> +                tuple, ret) != 0)
>           goto fail;
> -    if (full_tuple == NULL) {
> +    if (*ret == NULL) {
>           /*
>            * All indexes of a space must be consistent, i.e.
>            * if a tuple is present in one index, it must be
> @@ -3908,10 +3903,9 @@ next:
>                vy_lsm_name(it->lsm), vy_stmt_str(tuple));
>           goto next;
>       }
> -    *ret = tuple_bless(full_tuple);
> -    tuple_unref(full_tuple);
> -    if (*ret != NULL)
> -        return 0;
> +    tuple_bless(*ret);
> +    tuple_unref(*ret);
> +    return 0;
>   fail:
>       vinyl_iterator_close(it);
>       return -1;
> @@ -3997,16 +3991,12 @@ vinyl_index_get(struct index *index, const char *key,
>       const struct vy_read_view **rv = (tx != NULL ? vy_tx_read_view(tx) :
>                         &env->xm->p_global_read_view);
> 
> -    struct tuple *tuple;
> -    if (vy_lsm_full_by_key(lsm, tx, rv, key, part_count, &tuple) != 0)
> +    if (vy_lsm_full_by_key(lsm, tx, rv, key, part_count, ret) != 0)
>           return -1;
> -
> -    if (tuple != NULL) {
> -        *ret = tuple_bless(tuple);
> -        tuple_unref(tuple);
> -        return *ret == NULL ? -1 : 0;
> +    if (*ret != NULL) {
> +        tuple_bless(*ret);
> +        tuple_unref(*ret);
>       }
> -    *ret = NULL;
>       return 0;
>   }
> 
> diff --git a/test/box/misc.result b/test/box/misc.result
> index 8f94f5513..f7703ba8d 100644
> --- a/test/box/misc.result
> +++ b/test/box/misc.result
> @@ -332,7 +332,6 @@ t;
>     - 'box.error.UNKNOWN_UPDATE_OP : 28'
>     - 'box.error.WRONG_COLLATION_OPTIONS : 151'
>     - 'box.error.CURSOR_NO_TRANSACTION : 80'
> -  - 'box.error.TUPLE_REF_OVERFLOW : 86'
>     - 'box.error.ALTER_SEQUENCE : 143'
>     - 'box.error.INVALID_XLOG_NAME : 75'
>     - 'box.error.SAVEPOINT_EMPTY_TX : 60'
> @@ -360,7 +359,7 @@ t;
>     - 'box.error.VINYL_MAX_TUPLE_SIZE : 139'
>     - 'box.error.LOAD_FUNCTION : 99'
>     - 'box.error.INVALID_XLOG : 74'
> -  - 'box.error.PRIV_NOT_GRANTED : 91'
> +  - 'box.error.READ_VIEW_ABORTED : 130'
>     - 'box.error.TRANSACTION_CONFLICT : 97'
>     - 'box.error.GUEST_USER_PASSWORD : 96'
>     - 'box.error.PROC_C : 102'
> @@ -405,7 +404,7 @@ t;
>     - 'box.error.injection : table: <address>
>     - 'box.error.NULLABLE_MISMATCH : 153'
>     - 'box.error.LAST_DROP : 15'
> -  - 'box.error.NO_SUCH_ROLE : 82'
> +  - 'box.error.TUPLE_FORMAT_LIMIT : 16'
>     - 'box.error.DECOMPRESSION : 124'
>     - 'box.error.CREATE_SEQUENCE : 142'
>     - 'box.error.CREATE_USER : 43'
> @@ -414,66 +413,66 @@ t;
>     - 'box.error.SEQUENCE_OVERFLOW : 147'
>     - 'box.error.SYSTEM : 115'
>     - 'box.error.KEY_PART_IS_TOO_LONG : 118'
> -  - 'box.error.TUPLE_FORMAT_LIMIT : 16'
> -  - 'box.error.BEFORE_REPLACE_RET : 53'
> +  - 'box.error.INJECTION : 8'
> +  - 'box.error.INVALID_MSGPACK : 20'
>     - 'box.error.NO_SUCH_SAVEPOINT : 61'
>     - 'box.error.TRUNCATE_SYSTEM_SPACE : 137'
>     - 'box.error.VY_QUOTA_TIMEOUT : 135'
>     - 'box.error.WRONG_INDEX_OPTIONS : 108'
>     - 'box.error.INVALID_VYLOG_FILE : 133'
>     - 'box.error.INDEX_FIELD_COUNT_LIMIT : 127'
> -  - 'box.error.READ_VIEW_ABORTED : 130'
> +  - 'box.error.PRIV_NOT_GRANTED : 91'
>     - 'box.error.USER_MAX : 56'
> -  - 'box.error.PROTOCOL : 104'
> +  - 'box.error.BEFORE_REPLACE_RET : 53'
>     - 'box.error.TUPLE_NOT_ARRAY : 22'
>     - 'box.error.KEY_PART_COUNT : 31'
>     - 'box.error.ALTER_SPACE : 12'
>     - 'box.error.ACTIVE_TRANSACTION : 79'
>     - 'box.error.EXACT_FIELD_COUNT : 38'
>     - 'box.error.DROP_SEQUENCE : 144'
> -  - 'box.error.INVALID_MSGPACK : 20'
>     - 'box.error.MORE_THAN_ONE_TUPLE : 41'
> -  - 'box.error.RTREE_RECT : 101'
> -  - 'box.error.SUB_STMT_MAX : 121'
> +  - 'box.error.UPSERT_UNIQUE_SECONDARY_KEY : 105'
>     - 'box.error.UNKNOWN_REQUEST_TYPE : 48'
> -  - 'box.error.SPACE_EXISTS : 10'
> +  - 'box.error.SUB_STMT_MAX : 121'
>     - 'box.error.PROC_LUA : 32'
> +  - 'box.error.SPACE_EXISTS : 10'
>     - 'box.error.ROLE_NOT_GRANTED : 92'
> +  - 'box.error.UNSUPPORTED : 5'
>     - 'box.error.NO_SUCH_SPACE : 36'
>     - 'box.error.WRONG_INDEX_PARTS : 107'
> -  - 'box.error.DROP_SPACE : 11'
>     - 'box.error.MIN_FIELD_COUNT : 39'
>     - 'box.error.REPLICASET_UUID_MISMATCH : 63'
>     - 'box.error.UPDATE_FIELD : 29'
> +  - 'box.error.INDEX_EXISTS : 85'
>     - 'box.error.COMPRESSION : 119'
>     - 'box.error.INVALID_ORDER : 68'
> -  - 'box.error.INDEX_EXISTS : 85'
>     - 'box.error.SPLICE : 25'
>     - 'box.error.UNKNOWN : 0'
> +  - 'box.error.IDENTIFIER : 70'
>     - 'box.error.DROP_PRIMARY_KEY : 17'
>     - 'box.error.NULLABLE_PRIMARY : 152'
>     - 'box.error.NO_SUCH_SEQUENCE : 145'
>     - 'box.error.RELOAD_CFG : 58'
>     - 'box.error.INVALID_UUID : 64'
> -  - 'box.error.INJECTION : 8'
> +  - 'box.error.DROP_SPACE : 11'
>     - 'box.error.TIMEOUT : 78'
> -  - 'box.error.IDENTIFIER : 70'
>     - 'box.error.ITERATOR_TYPE : 72'
>     - 'box.error.REPLICA_MAX : 73'
> +  - 'box.error.NO_SUCH_ROLE : 82'
>     - 'box.error.MISSING_REQUEST_FIELD : 69'
>     - 'box.error.MISSING_SNAPSHOT : 93'
>     - 'box.error.WRONG_SPACE_OPTIONS : 111'
>     - 'box.error.READONLY : 7'
> -  - 'box.error.UNSUPPORTED : 5'
>     - 'box.error.UPDATE_INTEGER_OVERFLOW : 95'
> +  - 'box.error.RTREE_RECT : 101'
>     - 'box.error.NO_CONNECTION : 77'
>     - 'box.error.INVALID_XLOG_ORDER : 76'
> -  - 'box.error.UPSERT_UNIQUE_SECONDARY_KEY : 105'
> -  - 'box.error.ROLLBACK_IN_SUB_STMT : 123'
>     - 'box.error.WRONG_SCHEMA_VERSION : 109'
> -  - 'box.error.UNSUPPORTED_INDEX_FEATURE : 112'
> -  - 'box.error.INDEX_PART_TYPE_MISMATCH : 24'
> +  - 'box.error.ROLLBACK_IN_SUB_STMT : 123'
> +  - 'box.error.PROTOCOL : 104'
>     - 'box.error.INVALID_XLOG_TYPE : 125'
> +  - 'box.error.INDEX_PART_TYPE_MISMATCH : 24'
> +  - 'box.error.UNSUPPORTED_INDEX_FEATURE : 112'
>   ...
>   test_run:cmd("setopt delimiter ''");
>   ---
> diff --git a/test/box/select.result b/test/box/select.result
> index 4aed70630..6e6ccade1 100644
> --- a/test/box/select.result
> +++ b/test/box/select.result
> @@ -619,6 +619,11 @@ collectgarbage('collect')
>   ---
>   - 0
>   ...
> +-- gh-3224 resurrect tuple bigrefs
> +collectgarbage('stop')
> +---
> +- 0
> +...
>   s = box.schema.space.create('select', { temporary = true })
>   ---
>   ...
> @@ -628,22 +633,37 @@ index = s:create_index('primary', { type = 'tree' })
>   a = s:insert{0}
>   ---
>   ...
> -lots_of_links = {}
> +lots_of_links = setmetatable({}, {__mode = 'v'})
> +---
> +...
> +ref_count = 0
> +---
> +...
> +while (ref_count < 100000) do table.insert(lots_of_links, s:get{0}) ref_count = ref_count + 1 end
>   ---
>   ...
> +ref_count
> +---
> +- 100000
> +...
>   ref_count = 0
>   ---
>   ...
> -while (true) do table.insert(lots_of_links, s:get{0}) ref_count = ref_count + 1 end
> +for k, v in pairs(lots_of_links) do ref_count = ref_count + 1 end
>   ---
> -- error: Tuple reference counter overflow
>   ...
>   ref_count
>   ---
> -- 65531
> +- 100000
> +...
> +-- check that tuples are deleted after gc is activated
> +collectgarbage('collect')
> +---
> +- 0
>   ...
> -lots_of_links = {}
> +lots_of_links
>   ---
> +- []
>   ...
>   s:drop()
>   ---
> diff --git a/test/box/select.test.lua b/test/box/select.test.lua
> index 54c2ecc1c..f15c6e275 100644
> --- a/test/box/select.test.lua
> +++ b/test/box/select.test.lua
> @@ -124,12 +124,21 @@ test.random(s.index[0], 48)
>   s:drop()
> 
>   collectgarbage('collect')
> +
> +-- gh-3224 resurrect tuple bigrefs
> +
> +collectgarbage('stop')
>   s = box.schema.space.create('select', { temporary = true })
>   index = s:create_index('primary', { type = 'tree' })
>   a = s:insert{0}
> -lots_of_links = {}
> +lots_of_links = setmetatable({}, {__mode = 'v'})
>   ref_count = 0
> -while (true) do table.insert(lots_of_links, s:get{0}) ref_count = ref_count + 1 end
> +while (ref_count < 100000) do table.insert(lots_of_links, s:get{0}) ref_count = ref_count + 1 end
>   ref_count
> -lots_of_links = {}
> +ref_count = 0
> +for k, v in pairs(lots_of_links) do ref_count = ref_count + 1 end
> +ref_count
> +-- check that tuples are deleted after gc is activated
> +collectgarbage('collect')
> +lots_of_links
>   s:drop()
> 
>