5.7.16_10.57 Memory leak or bad config

In CentOS 7 operating system, I use Percona XtradB 5.7.16_10.57. DB size 63 gb, innodb table structure. Server consists of 48 GHz CPU, 80 gb memory and 300 gb ssd disk.
The problem is that continuous memory is decreasing by 2 bytes every minute, so memory usage is increasing. is this a problem?