Instruction stream tracing of multi-threaded processors

• US 9,996,354 B2
• Filed: 01/09/2015
• Issued: 06/12/2018
• Est. Priority Date: 01/09/2015
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Eisen, Lee E., Heller, Lisa C., Huffer, Michael T., Schwarz, Eric M.
• Primary Examiner(s): Rivera, Anibal
• Application Number:
  US14/592,936
• Publication Number:
  US 20160203073A1
• Time in Patent Office: 1,250 Days
• CPC Class Codes: G06F 11/1405 at machine instruction level
• CPC Class Codes: G06F 11/3447 Performance evaluation by modeling
• CPC Class Codes: G06F 11/3612 by runtime analysis performance monitoring G06F11/3466
• CPC Class Codes: G06F 11/3636 by tracing the execution of the program
• CPC Class Codes: G06F 9/30123 according to context, e.g. thread buffers
• CPC Class Codes: G06F 9/30141 Implementation provisions of register files, e.g. ports
• CPC Class Codes: G06F 9/3851 from multiple instruction streams, e.g. multistreaming
• CPC Class Codes: G06F 9/4881 Scheduling strategies for dispatcher, e.g. round robin, multi-level priority queues
• CPC Class Codes: G06F 9/4887 involving deadlines, e.g. rate based, periodic

Abstract

A method and apparatus for tracing instruction streams for a multi-threaded processor are disclosed herein. In one embodiment, the apparatus includes a last thread register configured to store a thread index that indicates a last executed thread, a tracing memory configured to store, within each of a plurality of storage locations, state information corresponding to a dispatch cycle for a multi-threaded processor, and a tracing control module configured to provide the state information to the tracing memory. The state information includes instruction information and a previous thread index. The state information may also include a flip bit that is used to determine a current insertion point within the tracing memory. A corresponding method is also disclosed herein.

Claims

1. A method for real-time tracing of instruction streams for a multi-threaded processor, the method comprising:

providing a multi-threaded processor comprising a tracing memory, a last thread register, and a tracing memory address counter configured to provide an address to the tracing memory;

storing, within the last thread register for each dispatch cycle of the multi-threaded processor, a current thread index for use as a last executed thread index during a next dispatch cycle;

storing, within a tracing memory at a location indicated by the tracing memory address counter for each dispatch cycle of the multi-threaded processor, state information corresponding to a current thread, wherein the current thread corresponds to one or more instructions that are dispatched for the current thread by a dispatch unit during that dispatch cycle of the multi-threaded processor;

wherein the state information comprises the last executed thread index provided by the last thread register and instruction information corresponding to the one or more instructions that are dispatched for the current thread by the dispatch unit during that dispatch cycle; and

wherein storing the state information including the last executed thread index occurs in real-time concurrent with instruction execution in the multi-threaded processor to enable reconstruction of thread sequencing.

2. The method of claim 1, wherein the state information comprises a flip bit that is used to determine a current insertion point within the tracing memory.

3. The method of claim 1, further comprising reconstructing state information for one or more threads from the state information within the tracing memory.

4. The method of claim 1, wherein the instruction information corresponds to a group of instructions dispatched in the same cycle.

5. The method of claim 1, wherein the instruction information indicates an operation code.

6. The method of claim 5, wherein the operation code corresponds to one or more micro-operations.

7. The method of claim 1, wherein the state information comprises one or more of program counter information, an execution unit identifier, a register identifier, a group identifier, and a pipeline identifier.

8. The method of claim 1, wherein the tracing memory is partitioned into a plurality of partitions and wherein each partition of the plurality of partitions corresponds to a particular thread.

9. The method of claim 8, wherein the tracing memory is selectively partitioned into the plurality of partitions.

10. An apparatus for real-time tracing of instruction streams for a multi-threaded processor, the apparatus comprising:

a last thread register configured to store for each dispatch cycle of the multi-threaded processor, a current thread index for use as a last executed thread index during a next dispatch cycle;

a tracing memory address counter configured to provide an address to the tracing memory for each dispatch cycle of the multi-threaded processor;

a tracing memory configured to store, for each dispatch cycle of the multi-threaded processor, within a storage location indicated by the tracing memory address counter, state information corresponding to a current thread, wherein the current thread corresponds to one or more instructions that are dispatched for the current thread by a dispatch unit during that dispatch cycle for the multi-threaded processor;

a tracing control module configured to provide the state information to the tracing memory;

wherein the state information comprises the last executed thread index provided by the last thread register and instruction information corresponding to the one or more instructions that are dispatched for the current thread by the dispatch unit; and

wherein the state information including the last executed thread index is stored in the tracing memory in real-time concurrent with instruction execution in the multi-threaded processor to enable reconstruction of thread sequencing.

11. The apparatus of claim 10, wherein the state information comprises a flip bit that is used to determine a current insertion point within the tracing memory.

12. The apparatus of claim 10, wherein the state information comprises instruction information.

13. The apparatus of claim 12, wherein the instruction information corresponds to a group of instructions dispatched in the same cycle.

14. The apparatus of claim 12, wherein the instruction information indicates an operation code.

15. The apparatus of claim 14, wherein the operation code corresponds to one or more micro-operations.

16. The apparatus of claim 10, wherein the state information comprises one or more of program counter information, an execution unit identifier, a register identifier, a group identifier, and a pipeline identifier.

17. The apparatus of claim 10, wherein the tracing memory is partitioned into a plurality of partitions and wherein each partition of the plurality of partitions corresponds to a particular thread.

18. The apparatus of claim 17, wherein the tracing control module is configured to selectively partition the tracing memory into the plurality of partitions.

19. The apparatus of claim 10, further comprising at least one additional tracing memory address counter configured to provide an address to the tracing memory.