Managing refresh operations for a memory device
Apparatus, systems, methods, and computer program products for managing refresh operations in memory devices are disclosed. An apparatus includes a memory device including a plurality of memory cells comprising an associated set of counters and a controller for the memory device. A controller is configured to randomly increment a counter associated with a memory cell in response to write disturbances for the memory cell. A controller is configured, in response to a counter being randomly incremented to a predetermined count, perform a refresh operation on a memory cell.
1. An apparatus comprising:
a controller for a memory device including a plurality of memory cells, the controller configured to:
in response to a write disturbance for a memory cell of the plurality of memory cells, randomly increment a first counter of a set of counters associated with the set of memory cells, the first counter associated with the memory cell, and
in response to the first counter being randomly incremented to a first predetermined count, perform a refresh operation on the memory cell.
2. The apparatus of claim 1 , wherein the controller, when randomly incrementing the first counter, is further configured to:
randomly generate a value in response to each write disturbance;
increment the first counter in response to the value being less than or equal to a probability value; and
maintain a current count in the first counter in response to the value being greater than the probability value.
3. The apparatus of claim 2 , wherein the value and the probability value are each values in the range of [0, 1).
4. The apparatus of claim 1 , wherein the first predetermined count is based on a size of the first counter.
5. The apparatus of claim 1 , wherein:
the plurality of memory cells are divided into sets of a plurality of memory cells; and
the controller is further configured to:
increment a second counter associated with a set of memory cells in response to a write disturbance for any memory cell in the set of memory cells, and
in response to the second counter being incremented to a second predetermined count, perform the refresh operation on each memory cell in the set of memory cells.
6. The apparatus of claim 5 , wherein the second predetermined count is based on a first size (b) of the second counter.
7. The apparatus of claim 6 , wherein:
the first size (b) of the second counter is less than or equal to a quantity (n) of write disturbances for a memory cell failure multiplied by a quantity (m) of memory cells in the set of memory cells (b≤n*m); and
the second predetermined count (c) is less than or equal to the first size (b) of the second counter (c≤b).
8. The apparatus of claim 6 , wherein the first predetermined count is based on a second size of the first counter.
9. The apparatus of claim 1 , wherein:
the memory device comprises one or more of a resistive random access memory (ReRAM) device, a magnetoresistive random access memory (MRAM) device, and a phase change memory (PCM) device; and
the refresh operation comprises one of a write-in-place operation and a copy forward operation.
10. A system comprising:
a storage class memory device including a plurality of sets of memory cells, each set of memory cells associated with a counter; and
a controller for the storage class memory device, the controller configured to:
increment a counter associated with a set of memory cells in response to a write disturbance for any memory cell in the set of memory cells, and
in response to the counter being incremented to a predetermined count, perform a refresh operation on each memory cell in the set of memory cells.
11. The system of claim 10 , wherein:
the first size (b) of the second counter is less than or equal to a quantity (n) of write disturbances for a memory cell failure multiplied by a quantity (m) of memory cells in the set of memory cells (b≤n*m); and
the second predetermined count (c) is less than or equal to the first size (b) of the second counter (c≤b).
12. The system of claim 10 , wherein the controller is further configured to:
perform wear-leveling operations to evenly distribute write operations among memory cells of each set of memory cells; and
utilize the counter in performing the wear-leveling operations.
13. The system of claim 10 , wherein:
the storage class memory device comprises one or more of a resistive random access memory (ReRAM) device, a magnetoresistive random access memory (MRAM) device, and a phase change memory (PCM) device; and
the refresh operation comprises one of a write-in-place operation and a copy forward operation.
14. An apparatus comprising:
means for randomly incrementing a first counter associated with a set of memory cells of a plurality of sets of memory cells of a write-in-place memory device in response to a write disturbance for the associated set of memory cells; and
means for performing a refresh operation on each memory cell in the set of memory cells in response to the first counter being randomly incremented to a first predetermined count.
15. The apparatus of claim 14 , wherein each set of memory cells comprises a single memory cell, the apparatus further comprising:
means for randomly generating a value in response to each write disturbance;
means for incrementing the first counter in response to the value being less than or equal to a probability value; and
means for maintaining a current count in the first counter in response to the value being greater than the probability value.
16. The apparatus of claim 14 , wherein the first predetermined count is based on a size of the first counter.
17. The apparatus of claim 14 , wherein:
each set of memory cells comprises a plurality of memory cells; and
the means for randomly incrementing the first counter comprises means for incrementing the first counter in response to a write disturbance for any memory cell in the set of memory cells.
18. The apparatus of claim 17 , further comprising:
a plurality of second counters associated with respective each memory cell of the plurality of memory cells;
means for randomly generating a value in response to the write disturbance;
means for incrementing a second counter associated with a memory cell for the write disturbance in response to the value being less than or equal to a probability value;
means for maintaining a current count in the second counter in response to the value being greater than the probability value; and
means for performing the refresh operation on the memory cell in response to the second counter being incremented to a second predetermined count.
19. The apparatus of claim 18 , wherein:
the first predetermined count is based on a first size of the first counter; and
the second predetermined count is based on a second size of the second counter.
20. The apparatus of claim 14 , wherein the write-in-place memory device comprises one or more of a resistive random access memory (ReRAM) device, a magnetoresistive random access memory (MRAM) device, and a phase change memory (PCM) device.