SYSTEM AND METHOD FOR LOCALITY DETECTION TO IDENTIFY READ OR WRITE STREAMS IN A MEMORY DEVICE

• US 20180314421A1
• Filed: 04/26/2017
• Published: 11/01/2018
• Est. Priority Date: 04/26/2017
• Status: Active Grant

• Current Assignee: Sandisk Technologies Incorporated (Western Digital Corporation)
• Original Assignee: Western Digital Technologies Incorporated (Western Digital Corporation)
• Inventors: Linkovsky, Vitali, Benisty, Shay, Guthrie, William, Virani, Scheheresade
• Granted Patent: US 10,564,853 B2
• Time in Patent Office: Days
• CPC Class Codes: G06F 13/4282 on a serial bus, e.g. I2C bus, SPI bus on daisy chain buses G06F13/4247
• CPC Class Codes: G06F 2213/0026 PCI express
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]

Abstract

Systems and methods for determining locality of an incoming command relative to previously identified write or read streams is disclosed. NVM Express (NVMe) implements a paired submission queue and completion queue mechanism, with host software on the host device placing commands into multiple submission queues. The memory device fetches the commands from the multiple submission queues, which results in the incoming commands being interspersed. In order to determine whether the incoming commands should be assigned to previously identified read or write streams, the locality of the incoming commands relative to the previously identified read or write streams is analyzed. One example of locality is proximity in address space. In response to determining locality, the incoming commands are assigned to the various streams.

Claims

1. A method comprising:

accessing an identified read stream, the identified read stream comprising one or more read commands and an address range, the address range determined based on addresses in the one or more read commands received in a memory device;

accessing an incoming command;

reviewing an address of the incoming command, wherein the address of the incoming command is not contiguous with the address range of the identified read stream;

analyzing proximity of the address of the incoming command with part or all of the address range of the identified read stream;

determining, based on the analysis of proximity, whether the incoming command is associated with the identified read stream; and

performing at least one access to non-volatile memory in the memory device based on the identified read stream.

2. The method of claim 1, wherein the incoming command comprises the address and a size of the incoming command;

wherein an address range for the incoming command is defined by the address and the size of the incoming command; and

wherein analyzing proximity of the incoming command with part or all of the address range in the identified read stream comprises analyzing proximity of the address range for the incoming command with part or all of the address range in the identified read stream.

3. The method of claim 2, wherein the proximity is based on an amount of data to read in at least one of the commands in the identified read stream.

4. The method of claim 3, wherein the identified read stream comprises a plurality of commands;

wherein a last command comprises the command last associated with the identified read stream; and

wherein the last command includes the amount of data to read.

5. The method of claim 2, wherein the proximity comprises a predetermined minimum proximity or a predetermined maximum proximity.

6. The method of claim 2, wherein the address range of the identified read stream is defined by a lower address and an upper address;

further comprising determining an address gap;

wherein analyzing proximity comprises;

determining an extended address range of the identified address stream, the extended address range being determined by extending the lower address by the address gap and by extending the upper address by the address gap; and

determining whether the address range of the incoming command at least partly overlaps with the extended address range of the identified address stream,

wherein determining, based on the analysis of proximity, whether the incoming command is associated with the identified read stream comprises;

in response to determining that the address range of the incoming command at least partly overlaps with the extended address range of the identified address stream, determining the incoming command is associated with the identified read stream; and

in response to determining that the address range of the incoming command does not at least partly overlap with the extended address range of the identified address stream, determining the incoming command is not associated with the identified read stream.

7. The method of claim 6, wherein the address gap is determined based on a predetermined minimum address gap, a predetermined maximum address gap, and a length of a command most recently associated with the identified read stream.

8. The method of claim 1, wherein performing at least one access to non-volatile memory in the memory device based on the identified read stream comprises performing a read look ahead in the non-volatile memory based on the identified read stream.

9. The method of claim 8, further comprising determining a direction of the identified read stream;

and

wherein the read look ahead is performed using the direction of the identified read stream.

10. The method of claim 9, wherein the address range of the identified read stream is defined by a lower address and an upper address;

wherein the direction of the identified read stream comprises a lower address direction and an upper address direction, the lower address direction including addresses less than the lower address, the upper address direction including addresses greater than the upper address; and

wherein determining the direction of the identified read stream comprises determining whether additional commands not yet associated with the identified read stream include addresses in the lower address direction or addresses in the upper address direction.

11. A non-volatile memory device comprising:

a non-volatile memory having a plurality of memory cells;

a communication interface configured to communicate with a host device; and

a controller in communication with the non-volatile memory and the communication interface, the controller configured to;

identify a write command stream, the write command stream including an address range;

receive a non-write command via the communication interface;

determine whether the non-write command is associated with the write command stream; and

in response to determining that the non-write command is associated with the write command stream, perform a speculative access of the non-volatile memory using part or all of the address range of the write command stream.

12. The non-volatile memory device of claim 11, wherein the non-write command comprises a read command.

13. The non-volatile memory device of claim 12, wherein the read command comprises a read address;

and

wherein the controller is configured to determine whether the read command is associated with the write command by determining whether the read address is within the address range of the write command stream.

14. The non-volatile memory device of claim 13, wherein the speculative access of the non-volatile memory comprises a read look ahead operation.

15. The non-volatile memory device of claim 14, wherein the controller is configured to perform the read look ahead operation in response to analyzing a single read command.

16. A non-volatile memory device comprising:

a non-volatile memory having a plurality of memory cells;

a communication interface configured to communicate with a host device; and

a controller in communication with the non-volatile memory and the communication interface, the controller configured to;

access an identified read stream, the identified read stream comprising an address range and one or more read commands from the host device, the address range defined by a lower address and an upper address for the one or more read commands received in a memory device;

determine whether additional commands not yet associated with the identified read stream include addresses in a lower address direction or addresses in an upper address direction, the lower address direction including addresses less than the lower address, the upper address direction including addresses greater than the upper address; and

performing a read look ahead of the non-volatile memory based, at least in part, on whether the identified read stream has addresses in the lower address direction or the upper address direction.

17. The non-volatile memory device of claim 16, wherein the identified read stream comprises a plurality of commands;

wherein a first command comprises the command first associated with the identified read stream;

wherein a last command comprises the command last associated with the identified read stream; and

wherein determining whether additional commands not yet associated with the identified read stream include addresses in the lower address direction or addresses in the upper address direction comprises comparing an address associated with the last command with an address associated with the first command.

18. A method comprising:

accessing an identified read stream, the identified read stream comprising one or more read commands and an address range, the address range determined based on addresses in the one or more read commands received in a memory device;

accessing an incoming command;

comparing an address of the incoming command with the address range of the identified read stream;

determining, based on the comparison, whether the incoming command is associated with the identified read stream; and

in response to determining that the incoming command is associated with the identified read stream, executing the incoming command by performing at least one operation on a volatile memory in the memory device without performing the at least one operation on a non-volatile memory in the memory device.

19. The method of claim 18, wherein the command comprises a write command;

and

wherein the at least one operation comprises saving data associated with the write command in the volatile memory, with saving of the data to the non-volatile memory deferred in an expectation that the data will be written again.

20. The method of claim 18, wherein the command comprises a read command;

and

wherein the at least one operation comprises reading data associated with the read command from the volatile memory without reading the data from the non-volatile memory.

21. A non-volatile memory device comprising:

a non-volatile memory having a plurality of memory cells;

a communication interface configured to communicate with a host device; and

means for accessing an identified read stream, the identified read stream comprising one or more read commands and an address range, the address range determined based on addresses in the one or more read commands received in a memory device;

means for accessing an incoming command received via the communication interface;

means for reviewing an address of the incoming command, wherein the address of the incoming command is not contiguous with the address range of the identified read stream;

means for analyzing proximity of the address of the incoming command with part or all of the address range of the identified read stream;

means for determining, based on the analysis of proximity, whether the incoming command is associated with the identified read stream; and

means for performing at least one access to the non-volatile memory based on the identified read stream.

22. The non-volatile memory device of claim 21, wherein the incoming command comprises the address and a size of the incoming command;

wherein an address range for the incoming command is defined by the address and the size of the incoming command; and

wherein the means for analyzing proximity of the incoming command with part or all of the address range in the identified read stream comprises means for analyzing proximity of the address range for the incoming command with part or all of the address range in the identified read stream.

23. The non-volatile memory device of claim 22, wherein the proximity is based on an amount of data to read in at least one of the commands in the identified read stream.