According to one embodiment, a memory system includes a buffer, a nonvolatile memory and a controller. The buffer is capable of storing packets up to a first upper limit number. The controller generates a packet related to access to the nonvolatile memory and stores the packet in the buffer. The controller classifies the packets into packets of a first type and packets of a second type. The number of packets of the second type allowed to be stored in the buffer is limited to a second upper limit number smaller than the first upper limit number. When the number of packets of the second type stored in the buffer is the second upper limit number or larger, the controller does not generate a second packet of the second type or does not store the second packet in the buffer.