System and method for utilizing history information in a memory device
Systems and methods for controlling blocks in a memory device using a health indicator (such as the failed bit count) for the blocks are disclosed. However, the health indicator may exhibit noise, thereby resulting in an unreliable indicator of the health of the blocks in the memory device. In order to filter out the noise, a rolling average of the health indicator may be determined, and compared to the current health indicator. The comparison with the rolling average may indicate whether the current health indicator is an outlier, and thus should not be used. The health indicator may also be used to predict a future health indicator for different blocks in the memory device. Using the predicted future health indicator, the use of the blocks may be changed in order to more evenly wear the blocks.
1. A method comprising:
performing in a memory device:
accessing a plurality of health indicators for a first section of memory in the memory device, the health indicators indicative of usability of the first section of memory;
accessing a plurality of health indicators for a second section of memory in the memory device, the health indicators indicative of usability of the second section of memory;
accessing a predetermined number of future cycles of operation;
determining a predetermined future cycle of operation of the memory device, the predetermined future cycle of operation of the memory device comprising adding the predetermined number of future cycles of operation to a current cycle of operation of the memory device;
determining, based n the plurality of health indicators for the first section of memory, a forecast for the health indicator for the first section of memory at the predetermined future cycle of operation of the memory device;
determining, based on the plurality of health indicators for the second section of memory, a forecast for the health indicator for the second section of memory at the predetermined future cycle of operation of the memory device;
determining, based on the forecast for the health indicator for the first section and the forecast for the health indicator for the second section, whether to perform a write operation on the first section of memory or on the second section of memory;
responsive to determining to perform the write operation on the first section of memory, performing the write operation on the first section of memory in order for the first section of memory to be usable at least until the predetermined future cycle of operation; and
responsive to determining to perform the write operation on the second section of memory, performing the write operation on the second section of memory in order for the second section of memory to be usable at least until the predetermined future cycle of operation.
2. The method of claim 1 , wherein the first section of memory comprises a first block of memory; and
wherein the second section of memory comprises a second block of memory.
3. The method of claim 2 , wherein determining the forecast for the health indicator for the first section of memory at the future cycle of operation of the memory device comprises:
fitting a polynomial to the plurality of health indicators for the first section of memory; and
examining the polynomial to determine the forecast for the health indicator for the first section of memory at the predetermined future cycle of operation of the memory device.
4. The method of claim 1 , wherein the first section of memory comprises a first block;
wherein the second section of memory comprises a second block;
wherein determining whether to perform the operation on the first section of memory or the second section of memory comprises:
comparing the forecast for the health indicator of the first block with the forecast for the health indicator of the second block; and
determining, based on the comparison, whether to perform the operation on the first block or the second block.
5. A memory device comprising:
health indicator forecasting circuitry configured to:
access a predetermined number of future cycles of operation;
determine a predetermined future cycle of operation of the memory device, the predetermined future cycle of operation of the memory device comprising adding the predetermined number of future cycles of operation to a current cycle of operation of the memory device;
forecast a health indicator at the predetermined future cycle of operation of the memory device for respective sections of memory of the memory device, the health indicator indicative of usability of the respective section of memory;
a comparison circuitry configured to compare the forecasted health indicators for the respective sections;
a write determination circuitry configured to determine one or more of the respective sections of the memory to write to based on the comparison of the forecasted health indicators for the respective sections in order for the one or more sections of memory to be usable at least until the predetermined future cycle of operation; and
write circuitry configured to write to the one or more of the respective sections of memory based on the write determination circuitry.
6. The memory device of claim 5 , wherein the respective sections of memory comprises respective blocks of memory.
7. The memory device of claim 5 , wherein the health indicator forecasting circuitry is configured to fit a polynomial to a plurality of health indicators for each of the respective blocks of memory.
8. The memory device of claim 5 , wherein the health indicator forecasting circuitry is configured to forecast the health indicator for a first block and to forecast the health indicator for a second block; and
wherein the write determination circuitry is configured to modify use of one or both of the first block or the second block such that a difference between the health indicator for the first block and the health indicator for the second block is decreased.