Device and Method for Scheduling Commands in a Solid State Drive to Reduce Peak Power Consumption Levels

• US 20170090802A1
• Filed: 09/30/2015
• Published: 03/30/2017
• Est. Priority Date: 09/30/2015
• Status: Active Grant

• Current Assignee: Kioxia Corporation
• Original Assignee: OCZ Storage Solutions Incorporated (Toshiba Corporation)
• Inventors: Margetts, Julien, Calder, Gary James
• Granted Patent: US 10,120,817 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 1/3275 Power saving in memory, e.g. RAM, cache
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 13/1689 Synchronisation and timing concerns synchronisation on a memory bus G06F13/4234
• CPC Class Codes: G06F 3/0625 Power saving in storage systems
• 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: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

The current consumed by flash memory devices on the channels of a solid-state drive (SSD) device will be in the form of a time varying waveform, characterized mainly by the types of commands being processed, and are often in the form of periods of constant levels interspersed with very short high current peaks or spikes. When multiple commands are being processed, significant high current peak demands and current surges can occur. The invention described herein is a device and method for scheduling commands to be processed in order to reduce the size of peak current demands and current surges. According to one embodiment of the invention, the device and method for scheduling a command uses look-up tables to determine the time to initiate the processing of the command by the flash memory devices.

Claims

1. A solid-state storage device comprising:

a processor;

an I/O interface configured to allow communication between the processor and a host computer system, wherein the processor is configured to receive an instruction from the host computer system via the I/O interface;

a controller unit connected to the processor, the controller unit further connected to one or more memory bus channels, wherein each memory bus channel is connected to one or more flash memory devices, the controller unit configured to initiate a processing of a command issued by the processor to a flash memory device in response to the processor receiving the instruction from the host device, the controller unit further configured to assign a timestamp to the command; and

a non-transitory storage memory connected to the controller unit, the storage memory storing a look-up table having one or more rows containing time regions when the command can be processed, each time region have a type identifier and a start time and an end time,

wherein the controller unit is further configured to evaluate a time difference between a timestamp of a command to be initiated and processed and a timestamp of a command previously initiated and being processed, and to retrieve the row of the look-up table indexed by the time difference, and if the time difference is found within any time region of a row of the look-up table having a type identifier of a first type, immediately initiating the processing of the command, and if the time difference is found within any time region of a row of the look-up table having a type identifier of a second type, initiating processing of the command at the end time of the time region with the second type identifier.

2. The solid-state storage device of claim 1, wherein the storage memory stores a plurality of look-up tables.

3. The solid-state storage device of claim 2, wherein the controller is configured to select a look-up table from the plurality of look-up tables based upon a type of the command to be initiated for processing and a type of the command previously initiated and being processed, or a maximum allowed peak current value.

4. The solid-state storage device of claim 2, wherein the controller is configured to index at least two look-up tables using the evaluated time difference.

5. The solid-state storage device of claim 4, wherein the controller is configured to use a time the first look-up table permits initiation of the processing as the time to be used to index the second look-up table.

6. The solid-state storage device of claim 1, wherein the look-up table is constructed such that the type identifier of the time regions are of the first type if a peak current consumed by the one or more flash memory devices by processing the command to be initiated and the command previously initiated is below a maximum allowed peak current value, and of the second type if the peak current consumed by the one or more flash memory devices by processing the command to be initiated and the command previously initiated will be above the maximum allowed peak current value.

7. The solid-state storage device of claim 1, wherein the look-up table is updated in real-time with adjustment values based on real time measurements of a current consumed by the one or more flash memory devices according to a type of command issued to the flash memory devices.

8. The solid-state storage device of claim 1, wherein the look-up table is updated in real-time with adjustment values based on an ambient temperature.

9. The solid-state storage device of claim 1, wherein the look-up table is updated in real-time with adjustment values based on an age of the flash memory devices.

10. The solid-state storage device of claim 1, wherein the look-up table is updated in real-time with adjustment values based on a number of program and erase cycles performed by the flash memory devices.

11. A method for scheduling the processing of commands on a solid-state drive comprising:

assigning a timestamp to a command to be processed on the solid state drive,

calculating a time difference between the timestamp of the command to be processed and a timestamp of a command previously processed;

indexing a look-up table using the time difference where the look-up table contains one or more rows containing time regions when the command to be processed can be processed, each time region having a type identifier and a start time and an end time;

initiating processing of the command to be processed immediately if the time difference is found to be within a time region having a type identifier of a first type; and

initiating processing of the command to be processed at the end time of a time region if the time difference is found to be within the time region having a type identifier of the second type.

12. The method in claim 11, further comprising indexing a plurality of look-up tables.

13. The method in claim 12, further comprising selecting a look-up table from the plurality of look-up tables, the selection based upon a type of command to be processed and a type of command previously processed, or a maximum allowed peak current value.

14. The method in claim 12, further comprising indexing a second look-up table using a time a first look-up table permits initiating processing of the command.

15. The method in claim 11, wherein the time regions of the look-up table have the type identifier of the first type if a peak current consumed by one or more flash memory devices processing the command to be processed and the command previously processed is below a maximum allowed peak current value, and having the second type if the peak current consumed by the flash memory devices by processing the command to be processed and the command previously processed is above the maximum allowed peak current value.

16. The method in claim 15, further comprising updating the look-up table in real-time with adjustment values based on real-time measurements of the current consumed by the flash memory devices according to a type of command issued to the flash memory devices.

17. The method in claim 15, further comprising updating the look-up table in real-time with adjustment values based on an ambient temperature.

18. The method in claim 15, further comprising updating the look up-table in real-time with adjustment values based on an age of the flash memory devices.

19. The method in claim 15, further comprising updating the look-up table in real-time with adjustment values based on a number of program and erase cycles performed by the flash memory devices.