The growing up ram issue is an expected behaviour of Redis at first data load, after restarts, writing the data to disk (snapshot process). Redis tends to allocate memory as much as it can unless you don't use "maxmemory" option at your conf file.
It allocates memory but not release immediately. Sometimes it takes hours, I saw such cases.
Well known fact about Redis is that, it can allocate memory up to twice size of the dataset it keeps.
I suggest you to wait couple of hours without any restart (Redis can work in this time, get/set operations etc.) and keep watching the memory.
Please check that too
Redis will not always free up (return) memory to the OS when keys are
removed. This is not something special about Redis, but it is how most
malloc() implementations work. For example if you fill an instance
with 5GB worth of data, and then remove the equivalent of 2GB of data,
the Resident Set Size (also known as the RSS, which is the number of
memory pages consumed by the process) will probably still be around
5GB, even if Redis will claim that the user memory is around 3GB. This
happens because the underlying allocator can't easily release the
memory. For example often most of the removed keys were allocated in
the same pages as the other keys that still exist.
