Memory controller configured to transmit interrupt signal if volatile memory has no data corresponding to address requested from source

A memory system comprising:

• a nonvolatile memory configured to store data;
• a volatile memory configured to store a part of the data stored in the nonvolatile memory;
• and
• a controller configured to:
• in response to receiving, from a requester, a first request that includes an address,
• in a case where first data is not stored in the volatile memory, the first data corresponding to the address included in the first request,
• read the first data from the nonvolatile memory;
• store the read first data into the volatile memory;
• and
• upon the first data being stored into the volatile memory, send, to the requester, first information indicating that the first data has been stored into the volatile memory.