Method and System for Limiting Write Command Execution

• US 20160313944A1
• Filed: 10/14/2015
• Published: 10/27/2016
• Est. Priority Date: 04/22/2015
• Status: Active Grant

• Current Assignee: SanDisk Technologies LLC (Western Digital Corporation)
• Original Assignee: SanDisk Enterprise IP LLC (Western Digital Corporation)
• Inventors: Hodgdon, John G., Jones, Ryan R., Higgins, James M.
• Granted Patent: US 9,778,878 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0613 in relation to throughput
• CPC Class Codes: G06F 3/0647 Migration mechanisms
• CPC Class Codes: G06F 3/0652 Erasing, e.g. deleting, data cleaning, moving of data to a wastebasket
• 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]
• CPC Class Codes: G06F 3/0688 Non-volatile semiconductor memory arrays

Abstract

Methods, systems and/or devices are used for limiting write command execution in a storage device comprising a set of non-volatile memory devices. In one aspect, the method includes (1) accessing in a holding queue host-specified write commands specified by a host system, each of the host-specified write commands specifying a number of pages to be written to the set of non-volatile memory devices; (2) in accordance with a determination that throttling is enabled: (3) determining a limit number of pages for a current throttle period in accordance with a throttle rate, the throttle rate being a maximum write rate for executing host-specified write commands; and (4) during the current throttle period, moving from the holding queue to a pending queue, for execution by the set of non-volatile memory devices, host-specified write commands whose total specified number of pages does not exceed the limit number of pages.

Claims

1. A method of operation in a non-volatile memory system having a set of non-volatile memory devices, comprising:

accessing in a holding queue one or more host-specified write commands specified by a host system, each of the one or more host-specified write commands specifying a number of pages to be written to the set of non-volatile memory devices of the non-volatile memory system;

in accordance with a determination that throttling is enabled;

determining a limit number of pages for a current throttle period in accordance with a throttle rate, the throttle rate being a maximum write rate for executing host-specified write commands; and

during the current throttle period, moving from the holding queue to a pending queue, for execution by the set of non-volatile memory devices, host-specified write commands whose total specified number of pages does not exceed the limit number of pages.

2. The method of claim 1, including:

receiving the one or more host-specified write commands from the host system; and

placing the one or more host-specified write commands in the holding queue.

3. The method of claim 1, including:

in accordance with a determination that the total number of pages specified by the one or more host-specified write commands in the holding queue does not exceed the limit number of pages for the current throttle period, moving, during the current throttle period, all the host-specified write commands in the holding queue to the pending queue.

4. The method of claim 1, including:

for the current throttle period, updating the limit number of pages in accordance with the throttle rate.

5. The method of claim 1, including:

with respect to the current throttle period, adding to the limit number of pages a credit number of pages, determined in accordance with the throttle rate, and subtracting from the limit number of pages the total number of pages specified by the host-specified write commands moved to the pending queue during a corresponding throttle period.

6. The method of claim 1, including:

with respect to a future throttle period, determining a limit number of pages for the future throttle period in accordance with a limit number of pages for a throttle period prior to the future throttle period and a credit number of pages for the future throttle period, wherein the credit number of pages for the future throttle period is based on a throttle rate of the future throttle period; and

during the future throttle period, moving from the holding queue to the pending queue, for execution by the set of non-volatile memory devices, host-specified write commands whose total specified number of pages exceeds the credit number of pages for the future throttle period, but does not exceed the limit number of pages for the future throttle period.

7. The method of claim 1, further comprising,

with respect to each throttle period of a sequence of throttle periods after the current throttle period, in accordance with a determination that throttling is enabled:

determining an updated limit number of pages in accordance with the throttle rate; and

moving from the holding queue to the pending queue, for execution by the set of non-volatile memory devices, host-specified write commands whose total specified number of pages does not exceed the updated limit number of pages.

8. The method of claim 1, further comprising:

prior to a predefined event, disabling throttling;

in accordance with a determination that throttling is disabled;

moving host-specified write commands to the pending queue for execution; and

after the predefined event, enabling throttling.

9. The method of claim 1, further comprising:

at predefined times, in accordance with a determination to enable throttling after throttling has been disabled, determining an initial throttle rate in accordance with a write rate during a previous time period during which throttling was disabled; and

updating the throttle rate with respect to each throttle period of a sequence of throttle periods after throttling is enabled.

10. The method of claim 9, wherein updating the throttle rate comprises:

comparing a current erase rate of the non-volatile memory system with a current end-of-life (EOL) erase rate of the non-volatile memory system;

in accordance with a first comparison result from the comparing, reducing the throttle rate; and

in accordance with a second comparison result from the comparing, increasing the throttle rate.

11. The method of claim 10, further comprising:

after increasing the throttle rate, comparing the increased throttle rate with the current EOL erase rate of the non-volatile memory system to generate a third comparison result; and

in accordance with the third comparison result, suspending throttling until the first comparison result is satisfied.

12. The method of claim 11, further comprising:

after suspending throttling, comparing the current erase rate of the non-volatile memory system with the current EOL erase rate of the non-volatile memory system; and

resuming throttling in accordance with a predefined comparison result from comparing the current erase rate of the non-volatile memory system with the current EOL erase rate of the non-volatile memory system.

13. The method of claim 1, wherein:

the holding queue and the pending queue are logical queues; and

both the holding queue and the pending queue are part of a single physical queue.

14. The method of claim 1, wherein the holding queue and the pending queue are distinct physical queues.

15. The method of claim 1, wherein the non-volatile memory system includes one or more flash memory devices.

16. A non-volatile memory system, comprising:

a set of non-volatile memory devices; and

a storage controller having one or more processors configured to execute instructions in one or more programs, wherein the storage controller is configured to perform operations comprising;

accessing in a holding queue one or more host-specified write commands specified by a host system, each of the one or more host-specified write commands specifying a number of pages to be written to the set of non-volatile memory devices of the non-volatile memory system;

in accordance with a determination that throttling is enabled;

determining a limit number of pages for a current throttle period in accordance with a throttle rate, the throttle rate being a maximum write rate for executing host-specified write commands; and

moving, during the current throttle period, from the holding queue to a pending queue, for execution by the set of non-volatile memory devices, host-specified write commands whose total specified number of pages does not exceed the limit number of pages.

17. The non-volatile memory system of claim 16, wherein the storage controller includes a throttle module configured to determine whether throttling is enabled, and in accordance with a determination that throttling is enabled, determine the limit number of pages for the current throttle period.

18. The non-volatile memory system of claim 16, wherein the storage controller includes a throttle rate determine module configured to determine the throttle rate.

19. The non-volatile memory system of claim 16, wherein the storage controller includes a throttle rate update module configured to update the throttle rate.

20. The non-volatile memory system of claim 16, wherein the storage controller includes a limit page update module configured to update the limit number of pages.

21. The non-volatile memory system of claim 16, wherein the storage controller includes a write commands determine module to move, during the current throttle period, from the holding queue to a pending queue, for execution by the set of non-volatile memory devices, host-specified write commands whose total specified number of pages does not exceed the limit number of pages.

22. The non-volatile memory system of claim 16, wherein the storage controller is configured to perform operations comprising:

in accordance with a determination that the total number of pages specified by the one or more host-specified write commands in the holding queue does not exceed the limit number of pages for the current throttle period, moving, during the current throttle period, all the host-specified write commands in the holding queue to the pending queue.

23. A non-transitory computer readable storage medium, storing one or more programs configured for execution by one or more processors of a non-volatile memory system, the one or more programs including instructions for performing operations comprising:

accessing in a holding queue one or more host-specified write commands specified by a host system, each of the one or more host-specified write commands specifying a number of pages to be written to the set of non-volatile memory devices of the non-volatile memory system;

in accordance with a determination that throttling is enabled;

determining a limit number of pages for a current throttle period in accordance with a throttle rate, the throttle rate being a maximum write rate for executing host-specified write commands; and

moving, during the current throttle period, from the holding queue to a pending queue, for execution by the set of non-volatile memory devices, host-specified write commands whose total specified number of pages does not exceed the limit number of pages.

24. The non-transitory computer readable storage medium of claim 23, wherein the one or more programs include instructions for performing operations comprising:

in accordance with a determination that the total number of pages specified by the one or more host-specified write commands in the holding queue does not exceed the limit number of pages for the current throttle period, moving, during the current throttle period, all the host-specified write commands in the holding queue to the pending queue.