I don't understand why my mysql eat a lot of memory even though I set innodb_buffer_poll_size to around 50%

here is my top

user@Mulia-Abadi:~$ top
top - 11:09:31 up 12 days, 16:30,  3 users,  load average: 5.43, 5.66, 5.75
Tasks: 395 total,   1 running, 284 sleeping,   0 stopped,   1 zombie
%Cpu(s): 34.5 us,  0.9 sy,  1.4 ni, 63.0 id,  0.3 wa,  0.0 hi,  0.0 si,  0.0 st

KiB Mem : 16089320 total,   168544 free, 13805028 used,  2115748 buff/cache

KiB Swap: 31231996 total, 30252540 free,   979456 used.  1948108 avail Mem

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND

10553 mysql     20   0 22.356g 0.012t  12644 S 544.0 80.0 363:08.77 mysqld

11251 user      30  10   52004  16708   3844 S  28.8  0.1   1:58.98 binaryring

here my.cnf

#
# The MySQL database server configuration file.
#
# You can copy this to one of:
# - "/etc/mysql/my.cnf" to set global options,
# - "~/.my.cnf" to set user-specific options.
# 
# One can use all long options that the program supports.
# Run program with --help to get a list of available options and with
# --print-defaults to see which it would actually understand and use.
#
# For explanations see
# http://dev.mysql.com/doc/mysql/en/server-system-variables.html

# This will be passed to all mysql clients
# It has been reported that passwords should be enclosed with ticks/quotes
# escpecially if they contain "#" chars...
# Remember to edit /etc/mysql/debian.cnf when changing the socket location.

# Here is entries for some specific programs
# The following values assume you have at least 32M ram

[mysqld_safe]
socket      = /var/run/mysqld/mysqld.sock
nice        = 0

[mysqld]
#
# * Basic Settings
#
#validate_password_policy=LOW
#federated
sql-mode=TRADITIONAL
innodb_lock_wait_timeout=50
transaction-isolation=READ-COMMITTED
skip-name-resolve
user        = mysql
pid-file    = /var/run/mysqld/mysqld.pid
socket      = /var/run/mysqld/mysqld.sock
port        = 3306
basedir     = /usr
datadir     = /var/lib/mysql
tmpdir      = /tmp
lc-messages-dir = /usr/share/mysql
skip-external-locking

# coba betulin error free blocks
innodb_buffer_pool_size=4G
#untuk Scheduler
event_scheduler=ON
#Untuk Skip Error jika free block Error
innodb_doublewrite=off
#
# Instead of skip-networking the default is now to listen only on
# localhost which is more compatible and is not less secure.
#bind-address           =127.0.0.1
bind-address        = 0.0.0.0
#
# * Fine Tuning
#
key_buffer_size     = 10M
max_allowed_packet  = 512M
thread_stack        = 192K
thread_cache_size       = 8
wait_timeout        = 3600
interactive_timeout = 3600
innodb_log_file_size    = 256M
#innodb_buffer_pool_instances = 4
#table_open_cache   = 3419
#join_buffer_size   = 1M
#read_rnd_buffer_size   = 1M
#sort_buffer_size   = 1M

# This replaces the startup script and checks MyISAM tables if needed
# the first time they are touched
myisam-recover-options  = BACKUP
max_connections        = 251
table_open_cache       = 3000
performance_schema=1
#thread_concurrency     = 10
#
# * Query Cache Configuration
#
query_cache_limit   = 1M
query_cache_size        = 80M
query_cache_type    = 1
#
# * Logging and Replication
#
# Both location gets rotated by the cronjob.
# Be aware that this log type is a performance killer.
# As of 5.1 you can enable the log at runtime!
#general_log_file        = /var/log/mysql/mysql.log
#general_log             = 1
#
# Error log - should be very few entries.
#
log_error = /var/log/mysql/error.log
#
# Here you can see queries with especially long duration
#slow_query_log     = 1
#slow_query_log_file    = /var/log/mysql/mysql-slow.log
#long_query_time = 2
#log-queries-not-using-indexes
#
# The following can be used as easy to replay backup logs or for replication.
# note: if you are setting up a replication slave, see README.Debian about
#       other settings you may need to change.
#server-id      = 1
#log_bin            = /var/log/mysql/mysql-bin.log
expire_logs_days    = 10
max_binlog_size     = 100M
#binlog_do_db       = include_database_name
#binlog_ignore_db   = include_database_name
#
# * InnoDB
#
# InnoDB is enabled by default with a 10MB datafile in /var/lib/mysql/.
# Read the manual for more InnoDB related options. There are many!
#
# * Security Features
#
# Read the manual, too, if you want chroot!
# chroot = /var/lib/mysql/
#
# For generating SSL certificates I recommend the OpenSSL GUI "tinyca".
#
# ssl-ca=/etc/mysql/cacert.pem
# ssl-cert=/etc/mysql/server-cert.pem
# ssl-key=/etc/mysql/server-key.pem
max_heap_table_size      = 128M
tmp_table_size       = 128M
thread_stack         = 256K
innodb_stats_on_metadata = 0
optimizer_search_depth   = 0

I am using
Welcome to Ubuntu 18.04.1 LTS (GNU/Linux 4.15.0-42-generic x86_64)

and the Mysql version is
5.7.24

I tried article https://www.percona.com/blog/2018/06/28/what-to-do-when-mysql-runs-out-of-memory-troubleshooting-guide/

but I'm still don't understand what cause it

When I run this

SELECT event_name, current_alloc, high_alloc 
FROM sys.memory_global_by_current_bytes 
WHERE current_count > 0;

the output is this

"event_name"    "current_alloc" "high_alloc"
"memory/sql/sp_head::main_mem_root" "137.86 MiB"    "228.69 MiB"
"memory/memory/HP_PTRS" "127.66 MiB"    "2.69 GiB"
"memory/performance_schema/table_handles"   "27.19 MiB" "27.19 MiB"
"memory/sql/TABLE"  "17.60 MiB" "19.32 MiB"
"memory/mysys/TREE" "15.15 MiB" "862.44 MiB"
"memory/performance_schema/events_statements_history_long"  "13.66 MiB" "13.66 MiB"
"memory/sql/thd::main_mem_root" "9.92 MiB"  "79.77 MiB"
"memory/performance_schema/events_statements_summary_by_digest.tokens"  "9.77 MiB"  "9.77 MiB"
"memory/performance_schema/events_statements_history_long.tokens"   "9.77 MiB"  "9.77 MiB"
"memory/performance_schema/events_statements_history_long.sqltext"  "9.77 MiB"  "9.77 MiB"
"memory/innodb/mem0mem" "9.08 MiB"  "14.71 MiB"
"memory/performance_schema/events_statements_summary_by_thread_by_event_name"   "8.67 MiB"  "8.67 MiB"
"memory/performance_schema/file_instances"  "8.25 MiB"  "8.25 MiB"
"memory/sql/JOIN_CACHE" "5.75 MiB"  "38.00 MiB"
"memory/performance_schema/memory_summary_by_thread_by_event_name"  "5.62 MiB"  "5.62 MiB"
"memory/performance_schema/events_statements_summary_by_digest" "4.88 MiB"  "4.88 MiB"
"memory/performance_schema/events_statements_summary_by_account_by_event_name"  "4.33 MiB"  "4.33 MiB"
"memory/performance_schema/events_statements_summary_by_host_by_event_name" "4.33 MiB"  "4.33 MiB"
"memory/performance_schema/events_statements_summary_by_user_by_event_name" "4.33 MiB"  "4.33 MiB"
"memory/performance_schema/table_shares"    "4.00 MiB"  "4.00 MiB"
"memory/performance_schema/events_statements_history"   "3.50 MiB"  "3.50 MiB"
"memory/performance_schema/events_statements_current"   "3.50 MiB"  "3.50 MiB"
"memory/performance_schema/events_waits_summary_by_thread_by_event_name"    "3.31 MiB"  "3.31 MiB"
"memory/performance_schema/events_transactions_history_long"    "3.28 MiB"  "3.28 MiB"
"memory/sql/TABLE_SHARE::mem_root"  "2.85 MiB"  "2.87 MiB"
"memory/performance_schema/memory_summary_by_account_by_event_name" "2.81 MiB"  "2.81 MiB"
"memory/performance_schema/memory_summary_by_host_by_event_name"    "2.81 MiB"  "2.81 MiB"
"memory/performance_schema/memory_summary_by_user_by_event_name"    "2.81 MiB"  "2.81 MiB"
"memory/performance_schema/table_io_waits_summary_by_index_usage"   "2.75 MiB"  "2.75 MiB"
"memory/innodb/row0sel" "2.64 MiB"  "3.94 MiB"
"memory/performance_schema/events_statements_history.tokens"    "2.50 MiB"  "2.50 MiB"
"memory/performance_schema/events_statements_history.sqltext"   "2.50 MiB"  "2.50 MiB"
"memory/performance_schema/events_statements_current.tokens"    "2.50 MiB"  "2.50 MiB"
"memory/performance_schema/events_statements_current.sqltext"   "2.50 MiB"  "2.50 MiB"
"memory/performance_schema/rwlock_instances"    "2.00 MiB"  "2.00 MiB"
"memory/performance_schema/mutex_instances" "1.75 MiB"  "1.75 MiB"
"memory/performance_schema/events_waits_history_long"   "1.68 MiB"  "1.68 MiB"
"memory/performance_schema/events_waits_summary_by_account_by_event_name"   "1.66 MiB"  "1.66 MiB"
"memory/performance_schema/events_waits_summary_by_host_by_event_name"  "1.66 MiB"  "1.66 MiB"
"memory/performance_schema/events_waits_summary_by_user_by_event_name"  "1.66 MiB"  "1.66 MiB"
"memory/performance_schema/prepared_statements_instances"   "1.62 MiB"  "1.62 MiB"
"memory/innodb/ha_innodb"   "1.62 MiB"  "2.35 MiB"
"memory/performance_schema/table_lock_waits_summary_by_table"   "1.34 MiB"  "1.34 MiB"
"memory/performance_schema/events_stages_summary_by_thread_by_event_name"   "1.17 MiB"  "1.17 MiB"
"memory/performance_schema/events_stages_history_long"  "1015.62 KiB"   "1015.62 KiB"
"memory/performance_schema/threads" "928.00 KiB"    "928.00 KiB"
"memory/performance_schema/events_transactions_history" "860.00 KiB"    "860.00 KiB"
"memory/sql/String::value"  "768.66 KiB"    "2.47 MiB"
"memory/performance_schema/events_stages_summary_by_account_by_event_name"  "600.00 KiB"    "600.00 KiB"
"memory/performance_schema/events_stages_summary_by_host_by_event_name" "600.00 KiB"    "600.00 KiB"
"memory/performance_schema/events_stages_summary_by_user_by_event_name" "600.00 KiB"    "600.00 KiB"
"memory/performance_schema/events_statements_summary_by_program"    "448.00 KiB"    "448.00 KiB"
"memory/performance_schema/events_waits_history"    "440.00 KiB"    "440.00 KiB"
"memory/performance_schema/events_stages_history"   "260.00 KiB"    "260.00 KiB"
"memory/performance_schema/file_handle" "256.00 KiB"    "256.00 KiB"
"memory/sql/Filesort_buffer::sort_keys" "0 bytes"   "19.42 MiB"
"memory/memory/HP_SHARE"    "210.02 KiB"    "1.85 MiB"
"memory/mysys/IO_CACHE" "128.02 KiB"    "13.78 MiB"
"memory/memory/HP_INFO" "140.17 KiB"    "1.19 MiB"
"memory/performance_schema/session_connect_attrs"   "128.00 KiB"    "128.00 KiB"
"memory/performance_schema/accounts"    "88.00 KiB" "88.00 KiB"
"memory/performance_schema/socket_instances"    "80.00 KiB" "80.00 KiB"
"memory/performance_schema/users"   "80.00 KiB" "80.00 KiB"
"memory/sql/Filesort_info::record_pointers" "2.72 KiB"  "1.44 MiB"
"memory/performance_schema/hosts"   "72.00 KiB" "72.00 KiB"
"memory/innodb/rem0rec" "64.69 KiB" "91.89 KiB"
"memory/performance_schema/memory_class"    "60.00 KiB" "60.00 KiB"
"memory/performance_schema/setup_objects"   "56.00 KiB" "56.00 KiB"
"memory/performance_schema/mutex_class" "52.50 KiB" "52.50 KiB"
"memory/innodb/btr0pcur"    "51.87 KiB" "81.33 KiB"
"memory/sql/NET::buff"  "48.02 KiB" "192.08 KiB"
"memory/performance_schema/setup_actors"    "40.00 KiB" "40.00 KiB"
"memory/sql/THD::sp_cache"  "39.92 KiB" "55.89 KiB"
"memory/performance_schema/stage_class" "37.50 KiB" "37.50 KiB"
"memory/performance_schema/statement_class" "36.19 KiB" "36.19 KiB"
"memory/performance_schema/events_statements_summary_global_by_event_name"  "34.68 KiB" "34.68 KiB"
"memory/performance_schema/cond_instances"  "32.00 KiB" "32.00 KiB"
"memory/performance_schema/file_class"  "25.00 KiB" "25.00 KiB"
"memory/sql/THD::Session_tracker"   "24.94 KiB" "100.51 KiB"
"memory/performance_schema/memory_summary_global_by_event_name" "22.50 KiB" "22.50 KiB"
"memory/performance_schema/events_transactions_summary_by_thread_by_event_name" "22.00 KiB" "22.00 KiB"
"memory/performance_schema/cond_class"  "20.00 KiB" "20.00 KiB"
"memory/innodb/trx0undo"    "17.88 KiB" "20.28 KiB"
"memory/myisam/MI_INFO" "14.92 KiB" "134.30 KiB"
"memory/innodb/os0event"    "13.41 KiB" "66.80 KiB"
"memory/sql/PROFILE"    "12.24 KiB" "15.38 KiB"
"memory/sql/THD::transactions::mem_root"    "12.05 KiB" "20.08 KiB"
"memory/performance_schema/events_transactions_summary_by_account_by_event_name"    "11.00 KiB" "11.00 KiB"
"memory/performance_schema/events_transactions_summary_by_host_by_event_name"   "11.00 KiB" "11.00 KiB"
"memory/performance_schema/events_transactions_summary_by_user_by_event_name"   "11.00 KiB" "11.00 KiB"
"memory/innodb/partitioning"    "10.86 KiB" "23.28 KiB"
"memory/performance_schema/rwlock_class"    "10.00 KiB" "10.00 KiB"
"memory/mysys/lf_node"  "9.77 KiB"  "9.77 KiB"
"memory/performance_schema/thread_class"    "9.38 KiB"  "9.38 KiB"
"memory/sql/Queue::queue_item"  "7.03 KiB"  "9.38 KiB"
"memory/mysys/lf_slist" "6.28 KiB"  "6.28 KiB"
"memory/myisam/record_buffer"   "5.17 KiB"  "480.61 KiB"
"memory/innodb/std" "4.94 KiB"  "31.92 KiB"
"memory/performance_schema/scalable_buffer" "4.92 KiB"  "4.92 KiB"
"memory/performance_schema/events_stages_summary_global_by_event_name"  "4.69 KiB"  "4.69 KiB"
"memory/sql/QUICK_RANGE_SELECT::alloc"  "3.97 KiB"  "654.84 KiB"
"memory/innodb/dict0dict"   "3.68 KiB"  "20.59 KiB"
"memory/performance_schema/socket_class"    "3.12 KiB"  "3.12 KiB"
"memory/sql/MYSQL_LOCK" "3.07 KiB"  "30.20 KiB"
"memory/sql/THD::variables" "2.94 KiB"  "5.25 KiB"
"memory/sql/user_var_entry" "1.55 KiB"  "4.73 KiB"
"memory/sql/Prepared_statement_map" "1.50 KiB"  "2.50 KiB"
"memory/vio/vio"    "1.45 KiB"  "5.81 KiB"
"memory/sql/THD::db"    "765 bytes" "993 bytes"
"memory/sql/TABLE::sort_io_cache"   "560 bytes" "36.09 KiB"
"memory/sql/THD::Session_sysvar_resource_manager"   "483 bytes" "1.89 KiB"
"memory/myisam/keycache_thread_var" "400 bytes" "560 bytes"
"memory/sql/acl_cache"  "309 bytes" "309 bytes"
"memory/sql/user_var_entry::value"  "128 bytes" "128 bytes"
"memory/mysys/MY_BITMAP::bitmap"    "56 bytes"  "176 bytes"
"memory/mysys/my_file_info" "34 bytes"  "4.34 KiB"
"memory/sql/my_bitmap_map"  "4 bytes"   "668 bytes"

when it query

SELECT  SUBSTRING_INDEX(
    SUBSTRING_INDEX(event_name, '/', 2), 
    '/', 
    -1
    )  AS event_type, 
    ROUND(SUM(CURRENT_NUMBER_OF_BYTES_USED)/1024/1024, 2) AS MB_CURRENTLY_USED
    FROM performance_schema.memory_summary_global_by_event_name 
    GROUP BY event_type
    HAVING MB_CURRENTLY_USED>0;

the result is this

"event_type"    "MB_CURRENTLY_USED"
"innodb"    "12.42"
"memory"    "6.11"
"myisam"    "0.04"
"mysys" "0.02"
"performance_schema"    "170.93"
"sql"   "141.86"

update:
I am using mysqltuner now
this is the result

     >>  MySQLTuner 1.7.2 - Major Hayden <major@mhtx.net>
 >>  Bug reports, feature requests, and downloads at http://mysqltuner.com/
 >>  Run with '--help' for additional options and output filtering

[--] Skipped version check for MySQLTuner script
[OK] Logged in using credentials from debian maintenance account.
[OK] Currently running supported MySQL version 5.7.24-0ubuntu0.18.04.1
[OK] Operating on 64-bit architecture

-------- Log file Recommendations ------------------------------------------------------------------
[--] Log file: /var/log/mysql/error.log(2K)
[OK] Log file /var/log/mysql/error.log exists
[OK] Log file /var/log/mysql/error.log is readable.
[OK] Log file /var/log/mysql/error.log is not empty
[OK] Log file /var/log/mysql/error.log is smaller than 32 Mb
[OK] /var/log/mysql/error.log doesn't contain any warning.
[!!] /var/log/mysql/error.log contains 15 error(s).
[--] 0 start(s) detected in /var/log/mysql/error.log
[--] 0 shutdown(s) detected in /var/log/mysql/error.log

-------- Storage Engine Statistics -----------------------------------------------------------------
[--] Status: +ARCHIVE +BLACKHOLE +CSV -FEDERATED +InnoDB +MEMORY +MRG_MYISAM +MyISAM +PERFORMANCE_SCHEMA
[--] Data in InnoDB tables: 5G (Tables: 2595)
[OK] Total fragmented tables: 0

-------- Security Recommendations ------------------------------------------------------------------
[OK] There are no anonymous accounts for any database users
[!!] User 'root@localhost' has no password set.
[--] Bug #80860 MySQL 5.7: Avoid testing password when validate_password is activated

-------- CVE Security Recommendations --------------------------------------------------------------
[OK] NO SECURITY CVE FOUND FOR YOUR VERSION

-------- Performance Metrics -----------------------------------------------------------------------
[--] Up for: 16h 38m 44s (1M q [22.915 qps], 1K conn, TX: 1G, RX: 152M)
[--] Reads / Writes: 61% / 39%
[--] Binary logging is disabled
[--] Physical Memory     : 15.3G
[--] Max MySQL memory    : 4.5G
[--] Other process memory: 331.1M
[--] Total buffers: 4.2G global + 1.1M per thread (251 max threads)
[--] P_S Max memory usage: 72B
[--] Galera GCache Max memory usage: 0B
[OK] Maximum reached memory usage: 4.3G (28.27% of installed RAM)
[OK] Maximum possible memory usage: 4.5G (29.36% of installed RAM)
[OK] Overall possible memory usage with other process is compatible with memory available
[OK] Slow queries: 0% (0/1M)
[OK] Highest usage of available connections: 39% (99/251)
[OK] Aborted connections: 0.06%  (1/1557)
[!!] Query cache may be disabled by default due to mutex contention.
[OK] Query cache efficiency: 90.3% (1M cached / 1M selects)
[OK] Query cache prunes per day: 0
[!!] Sorts requiring temporary tables: 26% (17K temp sorts / 67K sorts)
[!!] Joins performed without indexes: 12962
[OK] Temporary tables created on disk: 19% (27K on disk / 144K total)
[OK] Thread cache hit rate: 88% (172 created / 1K connections)
[!!] Table cache hit rate: 4% (2K open / 50K opened)
[OK] Open file limit used: 0% (20/5K)
[OK] Table locks acquired immediately: 100% (11K immediate / 11K locks)

-------- Performance schema ------------------------------------------------------------------------
[--] Memory used by P_S: 72B
[--] Sys schema is installed.

-------- ThreadPool Metrics ------------------------------------------------------------------------
[--] ThreadPool stat is disabled.

-------- MyISAM Metrics ----------------------------------------------------------------------------
[!!] Key buffer used: 19.2% (2M used / 10M cache)
[OK] Key buffer size / total MyISAM indexes: 10.0M/53.0K
[OK] Read Key buffer hit rate: 99.1% (1K cached / 15 reads)

-------- InnoDB Metrics ----------------------------------------------------------------------------
[--] InnoDB is enabled.
[--] InnoDB Thread Concurrency: 0
[OK] InnoDB File per table is activated
[!!] InnoDB buffer pool / data size: 4.0G/6.0G
[!!] Ratio InnoDB log file size / InnoDB Buffer pool size (12.5 %): 256.0M * 2/4.0G should be equal 25%
[!!] InnoDB buffer pool instances: 8
[--] Number of InnoDB Buffer Pool Chunk : 32 for 8 Buffer Pool Instance(s)
[OK] Innodb_buffer_pool_size aligned with Innodb_buffer_pool_chunk_size & Innodb_buffer_pool_instances
[OK] InnoDB Read buffer efficiency: 100.00% (10193882200 hits/ 10193933386 total)
[!!] InnoDB Write Log efficiency: 19.11% (9155 hits/ 47900 total)
[OK] InnoDB log waits: 0.00% (0 waits / 57055 writes)

-------- AriaDB Metrics ----------------------------------------------------------------------------
[--] AriaDB is disabled.

-------- TokuDB Metrics ----------------------------------------------------------------------------
[--] TokuDB is disabled.

-------- XtraDB Metrics ----------------------------------------------------------------------------
[--] XtraDB is disabled.

-------- RocksDB Metrics ---------------------------------------------------------------------------
[--] RocksDB is disabled.

-------- Spider Metrics ----------------------------------------------------------------------------
[--] Spider is disabled.

-------- Connect Metrics ---------------------------------------------------------------------------
[--] Connect is disabled.

-------- Galera Metrics ----------------------------------------------------------------------------
[--] Galera is disabled.

-------- Replication Metrics -----------------------------------------------------------------------
[--] Galera Synchronous replication: NO
[--] No replication slave(s) for this server.
[--] This is a standalone server.

-------- Recommendations ---------------------------------------------------------------------------
General recommendations:
    Control error line(s) into /var/log/mysql/error.log file
    Set up a Password for user with the following SQL statement ( SET PASSWORD FOR 'user'@'SpecificDNSorIp' = PASSWORD('secure_password'); )
    MySQL started within last 24 hours - recommendations may be inaccurate
    Adjust your join queries to always utilize indexes
    Increase table_open_cache gradually to avoid file descriptor limits
    Read this before increasing table_open_cache over 64: http://bit.ly/1mi7c4C
    Beware that open_files_limit (5000) variable
    should be greater than table_open_cache (2369)
Variables to adjust:
    query_cache_size (=0)
    query_cache_type (=0)
    sort_buffer_size (> 256K)
    read_rnd_buffer_size (> 256K)
    join_buffer_size (> 256.0K, or always use indexes with joins)
    table_open_cache (> 2369)
    innodb_buffer_pool_size (>= 5G) if possible.
    innodb_log_file_size * innodb_log_files_in_group should be equal to 1/4 of buffer pool size (=2G) if possible.
    innodb_buffer_pool_instances(=4)