Host interleaved erase operations for flash memory controller

• US 9,400,749 B1
• Filed: 01/28/2016
• Issued: 07/26/2016
• Est. Priority Date: 01/28/2013
• Status: Active Grant

• Current Assignee: Radian Memory Systems, Inc.
• Original Assignee: Radian Memory Systems, LLC
• Inventors: Kuzmin, Andrey V., Jadon, Mike, Mathews, Richard M.
• Primary Examiner(s): Birkhimer, Christopher D
• Application Number:
  US15/009,275
• Time in Patent Office: 180 Days
• US Class Current: 1/1
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/2022 Flash memory
• CPC Class Codes: G06F 2212/7207 management of metadata or control data
• CPC Class Codes: G06F 2212/7208 Multiple device management, e.g. distributing data over multiple flash devices
• CPC Class Codes: G06F 2212/7211 Wear leveling
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]
• CPC Class Codes: G11C 16/102 External programming circuits, e.g. EPROM programmers; In-circuit programming or reprogramming; EPROM emulators

Abstract

This disclosure provides for host-controller cooperation in managing NAND flash memory. The controller maintains information for each erase unit which tracks memory usage. This information assists the host in making decisions about specific operations, for example, initiating garbage collection, space reclamation, wear leveling or other operations. For example, metadata can be provided to the host identifying whether each page of an erase unit has been released, and the host can specifically then command each of consolidation and erase using direct addressing. By redefining host-controller responsibilities in this manner, much of the overhead association with FTL functions can be substantially removed from the memory controller, with the host directly specifying physical addresses. This reduces performance unpredictability and overhead, thereby facilitating integration of solid state drives (SSDs) with other forms of storage. The disclosed techniques are especially useful for direct-attached and/or network-attached storage.

Claims

1. A flash memory controller integrated circuit to receive memory access requests from a host, and to control a flash memory die, the flash memory die comprising independently erasable units of memory cells and for each one of the independently erasable units, independently programmable units of memory cells, the flash memory controller integrated circuit comprising:

at least one host interface to receive the memory access requests from the host and to exchange data with the host in association with the memory access requests;

at least one memory interface to program the data into the flash memory die, and to read the data therefrom, in fulfillment of the memory access requests;

circuitry to control performance of the memory access requests via the at least one memory interface;

circuitry to track page release state of each of the independently programmable units in the flash memory die, and to track erase state for each of the independently erasable units in the flash memory die;

circuitry to unsolicitedly transmit to the host via the at least one host interface information identifying the need for a maintenance operation to erase one of the independently erasable units, where the corresponding erase state indicates an unerased condition of the one of the independently erasable units, and where the corresponding page release states indicate that there are no unreleased pages of data still stored in the one of the independently erasable units;

circuitry to receive from the host via the at least one host interface an erase command responsive to the information transmitted to the host identifying the need for the maintenance operation, the erase command being interleaved with the memory access requests from the host, the erase command to be performed to recycle the one of the independently erasable units where the corresponding erase state indicates the unerased condition and where the corresponding page release states indicate that there are no unreleased pages of data still stored in the one of the independently erasable units; and

circuitry to control via the memory interface erasure of the one of the independently erasable units responsive to the erase command;

wherein the flash memory controller integrated circuit is dependent on receipt of the erase command from the host for purposes of scheduling erase of the one of the independently erasable units.

2. The flash memory controller integrated circuit of claim 1, wherein the flash memory die is a first flash memory die and the flash memory controller integrated circuit is further to control a second flash memory die, wherein the second flash memory die also comprises independently erasable units of memory cells and for each one of the independently erasable units, independently programmable units of memory cells, and wherein:

the at least one memory interface is to program data into the first flash memory die via a first channel and into the second flash memory die via a second channel;

the circuitry to track is also to track page release state of each of the independently programmable units of memory cells in the second flash memory die, and is also to track erase state for each of the independently erasable units of memory cells in the second flash memory die;

the circuitry to unsolicitedly transmit to the host the information identifying the need for the maintenance operation is to unsolicitedly transmit to the host via the at least one host interface information identifying the need for a maintenance operation to erase one of the independently erasable units in the second flash memory die, where the corresponding erase state indicates an unerased condition of the one of the independently erasable units, and where the corresponding page release states indicate that there are no unreleased pages of data still stored in the one of the independently erasable units;

the flash memory controller integrated circuit is dependent on an erase command from the host for purposes of scheduling erase of any of the independently erasable units in the first flash memory die and is dependent on an erase command from the host for purposes of scheduling erase of any of the independently erasable units in the second flash memory die; and

the circuitry to control is operable to control performance of erasure of one of the independently erasable units in the first flash memory die which is concurrent with control of performance of memory access requests via the at least one memory interface in the second flash memory die.

3. The flash memory controller integrated circuit of claim 1, wherein the flash memory die is a first flash memory die and the flash memory controller integrated circuit is further to control a second flash memory die, wherein the second flash memory die also comprises independently erasable units of memory cells and for each one of the independently erasable units, independently programmable units of memory cells, and wherein:

the at least one memory interface is to program data into the first flash memory die via a first channel and into the second flash memory die via a second channel;

the circuitry to track is also to track page release state of each of the independently programmable units of memory cells in the second flash memory die, and is also to track erase state for each of the independently erasable units of memory cells in the second flash memory die;

the circuitry to unsolicitedly transmit to the host the information identifying the need for the maintenance operation is to unsolicitedly transmit to the host via the at least one host interface information identifying the need for a maintenance operation to erase one of the independently erasable units in the second flash memory die, where the corresponding erase state indicates an unerased condition of the one of the independently erasable units, and where the corresponding page release states indicate that there are no unreleased pages of data still stored in the one of the independently erasable units;

the flash memory controller integrated circuit is dependent on an erase command from the host for purposes of scheduling erase of any of the independently erasable units in the first flash memory die and is dependent on an erase command from the host for purposes of scheduling erase of any of the independently erasable units in the second flash memory die; and

the circuitry to control is operable to control performance of erasure of one of the independently erasable units in the first flash memory die which is concurrent with control of performance of erasure of one of the independently erasable units in the second flash memory die.

4. The flash memory controller integrated circuit of claim 1, wherein:

the flash memory controller integrated circuit further comprises

circuitry to identify, dependent on tracked page release state, one or more independently programmable units of memory cells of the flash memory die corresponding to a first one of the independently erasable units, where the identified one or more independently programmable units of memory cells have not been released,

circuitry to transmit to the host via the at least one host interface information identifying the need to relocate data from the identified one or more independently programmable units, and

circuitry to transfer, responsive to a data relocation command from the host received via the at least one host interface, the data from the identified one or more independently programmable units to a new independently erasable unit of memory cells;

upon such transfer the flash memory controller integrated circuit is to update tracked page release state corresponding to the identified one or more independently programmable units to indicate a released state for each such independently programmable unit;

the circuitry to unsolicitedly transmit is to transmit the information identifying the need for the maintenance operation responsive to the update of the tracked page release state; and

the flash memory controller integrated circuit is dependent on a data relocation command from the host for purposes of scheduling data relocation from each of the independently programmable units in the flash memory die.

5. The flash memory controller integrated circuit of claim 1, wherein:

the circuitry to unsolicitedly transmit is to transmit to the host an address corresponding to the one of the independently erasable units in the flash memory die;

the erase command from the host contains the address and is specific to the address, the erase command from the host being interleaved with the memory access requests;

the transmission of information identifying the need for the maintenance operation to the host, and the manner in which the erase command is interleaved with the memory access requests, dictate when the independently erasable unit die is to be erased.

6. The flash memory controller integrated circuit of claim 1, wherein:

the circuitry to unsolicitedly transmit is to transmit to the host an address within the flash memory die of the one of the independently erasable units;

the erase command specifies the address within the flash memory die; and

the circuitry to control the erasure is to control erasure of the one of the independently erasable units irrespective of whether other ones of the independently erasable units in the flash memory die which are not specified by address transmitted to the host are also in an unerased condition, with no unreleased pages of data.

7. The flash memory controller integrated circuit of claim 1, wherein:

the circuitry to unsolicitedly transmit is to transmit identification of independently erasable units in the flash memory die which are in an unerased condition, with no unreleased pages of data, including the one of the independently erasable units;

the erase command is specific to the one of the independently erasable units; and

the circuitry to control the erasure is to control erasure of each one of identified independently erasable units, each responsive to an associated, dedicated erase command.

8. The flash memory controller integrated circuit of claim 1, wherein:

the flash memory controller integrated circuit further

comprises circuitry to track data age for each independently programmable unit of memory cells in the flash memory die, for any data stored in the corresponding independently programmable unit of memory cells,

circuitry to identify one of the independently programmable units of memory cells in the flash memory die for which the tracked data age satisfies a threshold condition,

circuitry to transmit to the host via the at least one host interface an address corresponding to the identified one, and

circuitry to transfer, responsive to a data relocation command from the host received via the at least one host interface, the data from the identified one of the independently programmable units to a new independently programmable unit of memory cells; and

the flash memory controller integrated circuit is dependent on the data relocation command from the host for purposes of scheduling transfer of the data from the identified one.

9. The flash memory controller integrated circuit of claim 8, wherein the threshold condition is programmable by command received by the flash memory controller integrated circuit from the host via the at least one host interface.

17. The flash memory device of claim 1, wherein:

the flash memory controller integrated circuit further

comprises circuitry to track data age for each independently programmable unit of memory cells in the flash memory die, for any data stored in the corresponding independently programmable unit of memory cells,

circuitry to identify one of the independently programmable units of memory cells in the flash memory die for which the tracked data age satisfies a threshold condition,

circuitry to transmit to the host via the at least one host interface an address corresponding to the identified one, and

circuitry to transfer, responsive to a data relocation command from the host received via the at least one host interface, the data from the identified one of the independently programmable units to a new independently programmable unit of memory cells; and

the flash memory controller integrated circuit is dependent on the data relocation command from the host for purposes of scheduling transfer of the data from the identified one.

18. The flash memory device of claim 17, embodied as a solid state drive, wherein the threshold condition is programmable by command received by the flash memory controller integrated circuit from the host via the at least one host interface.

10. A flash memory device, comprising:

a flash memory die comprising independently erasable units of memory cells and, for each one of the independently erasable units, independently programmable units of memory cells; and

a flash memory controller integrated circuit to receive memory access requests from a host and to control the flash memory die, the flash memory controller integrated circuit comprising

at least one host interface to receive the memory access requests from the host and to exchange data with the host in association with the memory access requests,

at least one memory interface to program the data into the flash memory die, and to read the data therefrom, in fulfillment of the memory access requests,

circuitry to control performance of the memory access requests via the at least one memory interface,

circuitry to track page release state of each of the independently programmable units in the flash memory die, and to track erase state for each of the independently erasable units in the flash memory die,

circuitry to unsolicitedly transmit to the host via the at least one host interface information identifying the need for a maintenance operation to erase one of the independently erasable units, where the corresponding erase state indicates an unerased condition of the one of the independently erasable units, and where the corresponding page release states indicate that there are no unreleased pages of data still stored in the one of the independently erasable units,

circuitry to receive from the host via the at least one host interface an erase command responsive to the information transmitted to the host identifying the need for the maintenance operation, the erase command being interleaved with the memory access requests from the host, the erase command to be performed to recycle the one of the independently erasable units where the corresponding erase state indicates the unerased condition and where the corresponding page release states indicate that there are no unreleased pages of data still stored in the one of the independently erasable units, and

circuitry to control via the memory interface erasure of the one of the independently erasable units responsive to the erase command;

wherein the flash memory controller integrated circuit is dependent on receipt of the erase command from the host for purposes of scheduling erase of the one of the independently erasable units.

11. The flash memory device of claim 10, wherein:

the flash memory die is a first flash memory die;

the flash memory device further comprises a second flash memory die, the second flash memory die also comprising independently erasable units of memory cells and for each one of the independently erasable units, independently programmable units of memory cells;

the flash memory controller integrated circuit is further to control the second flash memory die;

the at least one memory interface is to program data into the first flash memory die via a first channel and into the second flash memory die via a second channel;

the circuitry to track is also to track page release state of each of the independently programmable units of memory cells in the second flash memory die, and is also to track erase state for each of the independently erasable units of memory cells in the second flash memory die;

the circuitry to unsolicitedly transmit to the host the information identifying the need for the maintenance operation is to unsolicitedly transmit to the host via the at least one host interface information identifying the need for a maintenance operation to erase one of the independently erasable units in the second flash memory die, where the corresponding erase state indicates an unerased condition of the one of the independently erasable units, and where the corresponding page release states indicate that there are no unreleased pages of data still stored in the one of the independently erasable units;

the flash memory controller integrated circuit is dependent on an erase command from the host for purposes of scheduling erase of any of the independently erasable units in the first flash memory die and is dependent on an erase command from the host for purposes of scheduling erase of any of the independently erasable units in the second flash memory die; and

the circuitry to control is operable to control performance of erasure of one of the independently erasable units in the first flash memory die which is concurrent with control of performance of memory access requests via the at least one memory interface in the second flash memory die.

12. The flash memory device of claim 10, wherein:

the flash memory die is a first flash memory die;

the flash memory device further comprises a second flash memory die, the second flash memory die also comprising independently erasable units of memory cells and for each one of the independently erasable units, independently programmable units of memory cells;

the flash memory controller integrated circuit is further to control the second flash memory die;

the at least one memory interface is to program data into the first flash memory die via a first channel and into the second flash memory die via a second channel;

the circuitry to track is also to track page release state of each of the independently programmable units of memory cells in the second flash memory die, and is also to track erase state for each of the independently erasable units of memory cells in the second flash memory die;

the circuitry to unsolicitedly transmit to the host the information identifying the need for the maintenance operation is to unsolicitedly transmit to the host via the at least one host interface information identifying the need for a maintenance operation to erase one of the independently erasable units in the second flash memory die, where the corresponding erase state indicates an unerased condition of the one of the independently erasable units, and where the corresponding page release states indicate that there are no unreleased pages of data still stored in the one of the independently erasable units;

the flash memory controller integrated circuit is dependent on an erase command from the host for purposes of scheduling erase of any of the independently erasable units in the first flash memory die and is dependent on an erase command from the host for purposes of scheduling erase of any of the independently erasable units in the second flash memory die; and

the circuitry to control is operable to control performance of erasure of one of the independently erasable units in the first flash memory die which is concurrent with control of performance of erasure of one of the independently erasable units in the second flash memory die.

13. The flash memory device of claim 10, wherein:

the flash memory controller integrated circuit further comprises

circuitry to identify, dependent on tracked page release state, one or more independently programmable units of memory cells of the flash memory die corresponding to a first one of the independently erasable units, where the identified one or more independently programmable units of memory cells have not been released,

circuitry to transmit to the host via the at least one host interface information identifying the need to relocate data from the identified one or more independently programmable units, and

circuitry to transfer, responsive to a data relocation command from the host received via the at least one host interface, the data from the identified one or more independently programmable units to a new independently erasable unit of memory cells;

upon such transfer the flash memory controller integrated circuit is to update tracked page release state corresponding to the identified one or more independently programmable units to indicate a released state for each such independently programmable unit;

the circuitry to unsolicitedly transmit is to transmit the information identifying the need for the maintenance operation responsive to the update of the tracked page release state; and

the flash memory controller integrated circuit is dependent on a data relocation command from the host for purposes of scheduling data relocation from each of the independently programmable units in the flash memory die.

14. The flash memory device of claim 10, wherein:

the circuitry to unsolicitedly transmit is to transmit to the host an address corresponding to the one of the independently erasable units in the flash memory die; and

the erase command from the host contains the address and is specific to the address.

15. The flash memory device of claim 10, wherein:

the circuitry to unsolicitedly transmit is to transmit to the host an address within the flash memory die of the one of the independently erasable units;

the erase command specifies the address within the flash memory die; and

the circuitry to control the erasure is to control erasure of the one of the independently erasable units irrespective of whether other ones of the independently erasable units in the flash memory die which are not specified by address transmitted to the host are also in an unerased condition, with no unreleased pages of data.

16. The flash memory device of claim 10, wherein:

the circuitry to unsolicitedly transmit is to transmit identification of independently erasable units in the flash memory die which are in an unerased condition, with no unreleased pages of data, including the one of the independently erasable units;

the erase command is specific to the one of the independently erasable units; and

the circuitry to control the erasure is to control erasure of each one of identified independently erasable units, each responsive to an associated, dedicated erase command.

19. A flash memory controller integrated circuit to receive memory access requests from a host, and to control a flash memory die, the flash memory die comprising independently erasable units of memory cells and for each one of the independently erasable units, independently programmable units of memory cells, the flash memory controller integrated circuit comprising:

at least one host interface to receive the memory access requests from the host and to exchange data with the host in association with the memory access requests;

at least one memory interface to program the data into the flash memory die, and to read the data therefrom, in fulfillment of the memory access requests;

circuitry to control performance of the memory access requests via the at least one memory interface;

circuitry to track page release state of each of the independently programmable units in the flash memory die, and to track erase state for each of the independently erasable units in the flash memory die;

circuitry to transmit to the host via the at least one host interface information identifying one of the independently erasable units which is in an unerased state and which has at least one corresponding independently programmable units having an unreleased page of data;

circuitry to receive from the host via the at least one host interface a data relocation command, the data relocation command to specify movement of the unreleased page of data from the one of the independently erasable units to a new independently erasable unit, and to update page release state for the independently programmable units corresponding to the one of the independently erasable units;

circuitry to unsolicitedly transmit to the host via the at least one host interface information identifying the need for a maintenance operation to erase the one of the independently erasable units following fulfillment of the data relocation command, provided the erase state indicates an unerased condition of the one of the independently erasable units, and provided the corresponding, tracked page release states indicate that there are no unreleased pages of data still stored in the one of the independently erasable units; and

circuitry to receive an erase command responsive to the information transmitted to the host identifying the need for the maintenance operation, the erase command being interleaved with the memory access requests from the host, the erase command to be performed to recycle the one of the independently erasable units, and to control via the memory interface erasure of the one of the independently erasable units responsive to the erase command;

wherein the flash memory controller integrated circuit is dependent on receipt of the data relocation command from the host for purposes of scheduling transfer of the unreleased page of data, and

wherein the flash memory controller integrated circuit is further dependent on receipt of the erase command from the host for purposes of scheduling erase of the one of the independently erasable units.

20. The flash memory controller integrated circuit of claim 19, wherein the flash memory die is a first flash memory die and the flash memory controller integrated circuit is further to control a second flash memory die, wherein the second flash memory die also comprises independently erasable units of memory cells and for each one of the independently erasable units, independently programmable units of memory cells, and wherein:

the at least one memory interface is to program data into the first flash memory die via a first channel and into the second flash memory die via a second channel;

the circuitry to track is also to track page release state of each of the independently programmable units of memory cells in the second flash memory die, and is also to track erase state for each of the independently erasable units of memory cells in the second flash memory die;

the circuitry to unsolicitedly transmit to the host the information identifying the need for the maintenance operation is to unsolicitedly transmit to the host via the at least one host interface information identifying the need for a maintenance operation to erase one of the independently erasable units in the second flash memory die, where the corresponding erase state indicates an unerased condition of the one of the independently erasable units, and where the corresponding page release states indicate that there are no unreleased pages of data still stored in the one of the independently erasable units;

the flash memory controller integrated circuit is dependent on an erase command from the host for purposes of scheduling erase of any of the independently erasable units in the first flash memory die and is dependent on an erase command from the host for purposes of scheduling erase of any of the independently erasable units in the second flash memory die; and

the circuitry to control is operable to control performance of erasure of one of the independently erasable units in the first flash memory die which is concurrent with control of performance of erasure of one of the independently erasable units in the second flash memory die.

21. The flash memory controller integrated circuit of claim 20, wherein the one of the independently erasable units is in the first flash memory die, wherein the new independently erasable unit is free to be in the second flash memory die, and wherein the flash memory controller integrated circuit is operable to fulfill the data relocation command by movement of the unreleased page of data to the second flash memory die.

22. The flash memory controller integrated circuit of claim 19, wherein:

the circuitry to unsolicitedly transmit is to transmit to the host an address corresponding to the one of the independently erasable units in the flash memory die;

the erase command from the host contains the address and is specific to the address; and

the data relocation command and the erase command are each interleaved by the host with the memory access requests, such that the transmission of information identifying the need for the data relocation operation to the host, and the manner in which the data relocation command is interleaved with the memory access requests, dictate when the unreleased page is transferred, such that the transmission of information identifying the need for the maintenance operation to the host, and the manner in which the erase command is interleaved with the memory access requests, dictate when the independently erasable unit die is erased.

23. The flash memory controller integrated circuit of claim 19, wherein:

the circuitry to unsolicitedly transmit is to transmit identification of independently erasable units in the flash memory die which are in an unerased condition, with no unreleased pages of data, including the one of the independently erasable units;

the erase command is specific to the one of the independently erasable units; and

the circuitry to control the erasure is to control erasure of each one of identified independently erasable units, each responsive to an associated, dedicated erase command.