Dynamic response shaping for command aging
View Patent ↗The present invention provides a method, apparatus and article of manufacture for selecting commands to execute from a command queue in a data storage device. The present invention reduces maximum service times under random queued workloads by executing the oldest command in the queue at a constant and predetermined rate. This yields a minimal yet predictable performance penalty, while significantly reducing maximum service times.
1. A method for selecting commands for execution in a data storage device, the method comprising the steps of:
queuing one or more commands for the data storage device; and
selecting a next command for execution from the queued commands, wherein the oldest queued command is periodically selected as the next command at a constant, predetermined rate.
2. The method of claim 1 , wherein the oldest queued command is periodically selected as the next command every 1 of N times, wherein N is at least 2.
3. The method of claim 1 , wherein the oldest queued command is periodically selected as the next command only if the age of the oldest queued command exceeds a predetermined minimum age threshold value.
4. The method of claim 3 , wherein the minimum age threshold value is specified in a mode page byte within the data storage device.
5. A method for selecting commands for execution in a data storage device, the method comprising the steps of:
queuing one or more commands for the data storage device;
creating a group of one or more old commands selected from the queued commands; and
selecting a next command for execution from the queued commands, wherein one of the group of old commands is periodically selected as the next command at a constant, predetermined rate.
6. The method of claim 5 , wherein the step of creating a group of one or more old commands selected from the queued commands includes the steps of:
determining an age of the oldest queued command; and
selecting all commands that are within a predetermined delta age from the age of the oldest queued command.
7. The method of claim 5 , wherein the predetermined delta age is stored in a mode page byte within the data storage device.
8. The method of claim 5 , wherein the periodic selection of one of the group of old commands is made to minimize command execution time.
9. The method of claim 5 , wherein the periodic selection of one of the group of old commands is made only if the age of the selected command exceeds a predetermined minimum age threshold value.
10. The method of claim 9 , wherein the minimum age threshold value is specified in a mode page byte within the data storage device.
11. A data storage device, comprising:
one or more stacked disks; and
a controller for queuing one or more commands for the one or more stacked disks, and for selecting a next command for execution from the queued commands;
wherein the oldest queued command is periodically selected as the next command at a constant, predetermined rate.
12. The data storage device of claim 11 , wherein the oldest queued command is periodically selected as the next command every 1 of N times, wherein N is at least 2.
13. The data storage device of claim 11 , wherein the oldest queued command is periodically selected as the next command only if the oldest queued command exceeds a predetermined minimum age threshold value.
14. The data storage device of claim 11 , wherein the minimum age threshold value is specified in a mode page byte within the data storage device.
15. An article of manufacture embodying logic for selecting commands for execution in a data storage device, comprising:
queuing one or more commands for the data storage device; and
selecting a next command for execution from the queued commands, wherein the oldest queued command is periodically selected as the next command at a constant, predetermined rate.
16. The article of manufacture of claim 15 , wherein the oldest queued command is selected as the next command every 1 of N times, wherein N is at least 2.
17. The article of manufacture of claim 15 , wherein the oldest queued command is periodically selected as the next command only if the age of the oldest queued command exceeds a predetermined minimum age threshold value.
18. The article of manufacture of claim 17 , wherein the minimum age threshold value is specified in a mode page byte within the data storage device.