**Reported in Launchpad by yejr last update 09-11-2017 14:38:09

When i enable performance_schema and thread pool, Percona Server 5.7 will memory leak, and then lead to be oom-killed.
Although i upgrade the version from 5.7.17-11 to 5.7.18-16 this problem still happens.

My settiongs:
innodb_buffer_pool_size = 128M
innodb_buffer_pool_instances = 1
...
performance_schema = 1
performance_schema_instrument = '%=on'
...
thread_handling = "pool-of-threads"
thread_pool_max_threads = 10
thread_pool_size = 2
thread_pool_oversubscribe = 2
thread_pool_stall_limit = 100
extra_port = 3307

the memory of mysqld process will grow from 173MB to 903MB within 20min.

ps -ef | grep mysqld
> 925624 ./bin/mysqld --defaults-file=/etc/my.cnf-5.7

mysql -e "select event_name,SUM_NUMBER_OF_BYTES_ALLOC from memory_summary_global_by_event_name order by SUM_NUMBER_OF_BYTES_ALLOC desc LIMIT 10;" performance_schema
event_name SUM_NUMBER_OF_BYTES_ALLOC
memory/innodb/mem0mem 17933218707
memory/memory/HP_PTRS 3030236768
memory/sql/thd::main_mem_root 1078226976
memory/sql/Filesort_buffer::sort_keys 538117200
memory/sql/String::value 454065560
memory/sql/TABLE 425176683
memory/mysys/IO_CACHE 261595752
memory/mysys/MY_DIR 237420552
memory/performance_schema/events_statements_summary_by_thread_by_event_name 162555904
memory/innodb/buf_buf_pool 139722752

mysql -e "select thread_id, event_name, SUM_NUMBER_OF_BYTES_ALLOC from memory_summary_by_thread_by_event_name order by SUM_NUMBER_OF_BYTES_ALLOC desc limit 20" performance_schema
>>
thread_id event_name SUM_NUMBER_OF_BYTES_ALLOC
1 memory/innodb/buf_buf_pool 139722752
1 memory/sql/THD::Session_tracker 34062822
1 memory/sql/thd::main_mem_root 32576208
1 memory/sql/NET::buff 32148279
2206 memory/innodb/mem0mem 26965020
2518 memory/innodb/mem0mem 26963324
1988 memory/innodb/mem0mem 26938940
3775 memory/innodb/mem0mem 26938940
2692 memory/innodb/mem0mem 26853572
328 memory/innodb/mem0mem 26827964
104 memory/innodb/mem0mem 26102225
1920 memory/innodb/mem0mem 21829092
1 memory/sql/XID 19924544
1 memory/innodb/log0log 16865840
1 memory/sql/THD::transactions::mem_root 16217728
1209 memory/innodb/mem0mem 14509563
1 memory/innodb/hash0hash 11613000
1988 memory/sql/Filesort_buffer::sort_keys 9087712
2518 memory/sql/Filesort_buffer::sort_keys 9087712
2206 memory/sql/Filesort_buffer::sort_keys 9087712