Adaptive host memory buffer traffic control based on real time feedback
Boot code is loaded to the data storage device controller in a flexible manner by being able to receive chunks of the boot code from two separate locations, the host memory buffer (HMB) and the memory device, which may be a NAND device. Part of the boot code may be received from the HMB and another part of the boot code may be received from the memory device. If either the HMB or the memory device can deliver the chunks faster than the other, then the controller can receive the chunks from the faster location and periodically confirm the speed of delivery to ensure the boot code latency is optimized. The controller is configured to track an HMB turnaround latency and derive whether a next request should be sent to the HMB or the memory device when the data is present in both the HMB and the memory device.
1 . A data storage device, comprising:
a memory device; and
a controller coupled to the memory device, wherein the controller is configured to:
track a turnaround latency of another memory device, wherein the another memory device is external to the data storage device;
comparing the turnaround latency to a threshold latency to derive whether a next request should be sent to the another memory device or the memory device, wherein the threshold latency is based on:
an average latency of a number of previous read requests to the another memory device; or
a maximum latency of the number of previous read requests to the another memory device; and
send a next request to the another memory device or the memory device based on whether a same data is present in both the another memory device and the memory device.
2 . The data storage device of claim 1 , wherein the turnaround latency is an amount of time to read the same data from the another memory device.
3 . The data storage device of claim 1 , wherein the another memory device is a host memory buffer (HMB).
4 . The data storage device of claim 1 , wherein the controller is further configured to send the next request to the another memory device when the turnaround latency is less than the threshold latency.
5 . The data storage device of claim 1 , wherein the controller is further configured to send the next request to the memory device when the turnaround latency is greater than or equal to the threshold latency.
6 . The data storage device of claim 1 , wherein the sending further comprises setting an indication to either the another memory device or the memory device based on the comparing.
7 . The data storage device of claim 1 , wherein the controller is further configured to determine whether a read request address corresponding to the next request is present in the another memory device.