Hardware controlled instruction pre-fetching

Patent metadata

Field	Value
Publication number	US-10120713-B2
Application number	US-201615202160-A
Country	US
Kind code	B2
Filing date	Jul 5, 2016
Priority date	Jul 5, 2016
Publication date	Nov 6, 2018
Grant date	Nov 6, 2018

Abstract

A task control circuit maintains, in response to task event information, a task information queue that includes task information for a plurality of tasks. Based upon the task information in the task information queue, a future task switch condition is identified as corresponding to a task switch time for a particular task of the plurality of tasks. A load start time is determined for a set of instructions for the particular task. A pre-fetch request is generated to load the set of instructions for the particular task into the memory circuit. The pre-fetch request is forwarded to a hardware loader circuit. In response to the task switch time, a task event trigger is generated for the particular task. The hardware loader circuit is used to load, in response to the pre-fetch request, the set of instructions from a non-volatile memory into the memory circuit.

First claim

What is claimed is:

1. A system for loading and executing a plurality of tasks under the control of an operating system (OS), the system comprising:
a computer processor circuit configured to execute software instructions for the OS and the plurality of tasks;
a memory circuit configured to store the software instructions and coupled to the computer processor circuit to provide the software instructions to the computer processor circuit;
a hardware loader circuit coupled to the memory circuit and configured to load software instructions into the memory circuit; and
a task control circuit coupled to the computer processor circuit and the memory circuit and configured to:
maintain, in response to task event information, a task information queue that includes task information for the plurality of tasks;
identify, based upon the task information in the task information queue, a future task switch condition corresponding to a task switch time for a particular task of the plurality of tasks;
determine, based upon the task information and the task switch time, a load start time for a set of instructions for the particular task by being further configured to:
determine a load anticipation time for the particular task as a function of a size of the set of instructions and access time for a non-volatile memory circuit configured to store the set of instructions, and
subtract the load anticipation time from the task switch time to result in the load start time;

generate, in response to the load start time, a pre-fetch request to load the set of instructions for the particular task into the memory circuit; and
forward the pre-fetch request to the hardware loader circuit.

2. The system of claim 1 , wherein the OS is designed to maintain a set of task information in the memory circuit and wherein at least some of the task information in the task information queue is a copy of the task information maintained by the OS.

3. The system of claim 2 , wherein the task information queue contains additional data not present in the set of task information maintained by the OS.

4. The system of claim 2 , wherein the task control circuit is configured to maintain consistency between the task information queue and the task information maintained by the OS by being further configured to implement at least one of:
directly access the memory circuit and the task information maintained by the OS; and
invoke software code within the OS to access the memory circuit and the task information maintained by the OS.

5. The system of claim 1 , wherein the task control circuit is further configured to generate, in response to the task switch time, a task event trigger for the particular task, wherein the task event trigger for the particular task includes at least one of a generated interrupt and a set register value for a register accessible by the computer processor circuit.

6. The system of claim 1 , wherein the hardware loader circuit is configured to serialize load requests for the pre-fetch request by generating a series of individual load requests for the set of instructions.

7. The system of claim 1 , wherein the task control circuit is configured to generate multiple pre-fetch requests each containing a respective and different subset of the set of instructions.

8. The system of claim 1 , wherein the task control circuit is configured to identify the future task switch condition by determining that a priority for the particular task is higher than a priority for other tasks in the task information queue.

9. The system of claim 1 , wherein the task control circuit is configured to identify the future task switch condition by identifying an expiration time for a time slice; and determining that the particular task is assigned to a subsequent time slice.

10. The system of claim 1 wherein the OS is a real time OS; the computer processor circuit is located on an integrated circuit (IC) die and wherein the hardware loader circuit is configured to retrieve the set of instructions from a non-volatile memory circuit is a programmable read-only memory and external to the IC die.

11. The system of claim 10 , wherein the task information queue includes task entries that specify a start address location and an end address location for the set of instructions in the non-volatile memory circuit.

12. A method for use with a computer processor circuit configured to execute software instructions stored in a memory circuit and for an operating system (OS) and a plurality of tasks under control of the OS, the method comprising:
performing, by a task control circuit coupled to the computer processor circuit and the memory circuit:
maintaining, in response to task event information, a task information queue that includes task information for the plurality of tasks;
identifying, based upon the task information in the task information queue, a future task switch condition corresponding to a task switch time for a particular task of the plurality of tasks;
determining, based upon the task information and the task switch time, a load start time for a set of instructions for the particular task by:
determining a load anticipation time for the particular task as a function of a size of the set of instructions and access time for a non-volatile memory circuit configured to store the set of instructions, and
subtracting the load anticipation time from the task switch time to result in the load start time;

generating, in response to the load start time, a pre-fetch request to load the set of instructions for the particular task into the memory circuit;
forwarding the pre-fetch request to a hardware loader circuit; and
generating, in response to the task switch time, a task event trigger for the particular task; and
using the hardware loader circuit to load, in response to the pre-fetch request, the set of instructions from a non-volatile memory into the memory circuit.

13. The method of claim 12 , further comprising, maintaining, by the OS, a set of task information in the memory circuit and wherein at least some of the task information in the task information queue is a copy of the task information maintained by the OS.

14. The method of claim 13 , wherein the task information queue contains additional data not present in the set of task information maintained by the OS.

15. The method of claim 13 , further comprising using the task control circuit to maintain consistency between the task information queue and the task information maintained by the OS by at least one of:
directly accessing the memory circuit and the task information maintained by the OS; and
invoking software code within the OS to access the memory circuit and the task information maintained by the OS.

16. The method of claim 12 , wherein the generating the task event trigger for the particular task includes at least one of: generating an interrupt and setting of a register value that is accessible by the computer processor circuit.

17. The method of claim 12 , further comprising using the hardware loader circuit to serialize load requests for the pre-fetch request by generating a series of individual load requests for the set of instructions.

18. The method of claim 12 , further comprising using the task control circuit to generate multiple pre-fetch requests each containing a respective and different subset of the set of instructions.

19. The method of claim 12 , further comprising using the task control circuit to identify the future task switch condition by determining that a priority for the par

Assignees

• Freescale Semiconductor Inc
• Nxp Usa Inc

Inventors

• Rohleder Michael
• Singer Stefan
• Gerster Jochen

Classifications

• G06F9/4806

  Task transfer initiation or dispatching · CPC title

• G06F12/08

  in hierarchically structured memory systems, e.g. virtual memory systems · CPC title

• G06F9/4843

  by program, e.g. task dispatcher, supervisor, operating system · CPC title

• G06F9/48

  Program initiating; Program switching, e.g. by interrupt · CPC title

• G06F9/461

  Saving or restoring of program or task context · CPC title