Multiprocessor system with multiple concurrent modes of execution

Patent metadata

Field	Value
Publication number	US-9501333-B2
Application number	US-201314143783-A
Country	US
Kind code	B2
Filing date	Dec 30, 2013
Priority date	Jan 8, 2010
Publication date	Nov 22, 2016
Grant date	Nov 22, 2016

Abstract

A multiprocessor system supports multiple concurrent modes of speculative execution. Speculation identification numbers (IDs) are allocated to speculative threads from a pool of available numbers. The pool is divided into domains, with each domain being assigned to a mode of speculation. Modes of speculation include TM, TLS, and rollback. Allocation of the IDs is carried out with respect to a central state table and using hardware pointers. The IDs are used for writing different versions of speculative results in different ways of a set in a cache memory.

First claim

The invention claimed is:

1. A computer-implemented method for carrying out operations in a multiprocessor system, the method comprising:
recognizing by a processor of the multiprocessor system a need for speculative execution of a program thread running within the processor;
allocating at least one speculation identification (ID) number to the program thread running speculatively;
maintaining by the at least one processor, a directory based speculation control responsive to the speculation identification number;
counting by the at least one processor instances of use of the speculation identification number associated with the thread being active in the multiprocessor system; and
preventing by the at least one processor, the speculation identification number from being allocated to a new thread until the counting indicates no instances of use of that ID being active in the system, said operations further comprising:
counting instances of a group of the speculation IDs together;
allowing IDs of the group to become available for allocation responsive to the counting;
managing a pool of speculation IDs in accordance with a plurality of domains, such that IDs are allocated independently for each domain; and
allocating a mode of speculative execution to each domain.

2. The method of claim 1 , wherein the operations comprise: maintaining a central state table indicating a state of the speculation ID.

3. The method of claim 2 , wherein the state table indicates one of the following states for the speculation ID: available, committed, speculative, invalid.

4. The method of claim 1 , wherein the mode of speculative execution comprises one or more of transactional memory (TM), thread level speculation (TLS), and rollback.

5. The method of claim 1 , wherein the operations comprise implementing two distinct modes of speculation to be used concurrently.

6. The method of claim 5 , wherein at least two domains are allocated to respective different modes of speculative execution.

7. The method of claim 1 , wherein the managing and allocating are conducted within a cache memory of the system.

8. A multiprocessor system comprising
a plurality of processors, the processors running threads of program code in parallel in accordance with speculative execution; and
each processor of said plurality having a cache, each processor configured to:
recognize a need for speculative execution of a program thread running within the processor;
allocate at least one speculation identification number to the program thread executing speculatively;
maintain in the cache, a directory based speculation control responsive to the speculation identification number;
count instances of use of the speculation identification number being active in the multiprocessor system; and
prevent the speculation identification number from being allocated to a new thread until the counting indicates no instances of use of that ID being active in the system, said

processor further configured to perform operations comprising:
count instances of a group of the speculation IDs together; and
allow IDs of the group to become available for allocation responsive to the counting;
manage a pool of speculation IDs in accordance with a plurality of domains, such that IDs are allocated independently for each domain; and
allocate a mode of speculative execution to each domain.

9. The system of claim 8 , wherein the operations comprise:
maintaining a central state table indicating a state of the speculation ID.

10. The system of claim 9 , wherein the state table indicates one of the following states for the speculation ID: available, committed, speculative, invalid.

11. The system of claim 8 , wherein the mode of speculative execution comprises one or more of transactional memory (TM), thread level speculation (TLS), and rollback.

12. The system of claim 8 , wherein the operations comprise implementing two distinct modes of speculation to be used concurrently.

13. The system of claim 12 , wherein at least two domains are allocated to respective different modes of speculative execution.

14. The system of claim 8 , wherein the managing and allocating are conducted within a cache memory of the system.

Assignees

• IBM

Inventors

• Ahn Daniel
• Ceze Luis H
• Chen Dong Chen
• Gara Alan
• Heidelberger Philip
• Ohmacht Martin

Classifications

• G06F12/08

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

• G06F9/524 Primary

  Deadlock detection or avoidance · CPC title

• G06F12/0842 Primary

  for multiprocessing or multitasking · CPC title

• G06F12/084

  with a shared cache · CPC title