Region pattern-matching hardware prefetcher

Patent metadata

Field	Value
Publication number	US-12360907-B2
Application number	US-202217957795-A
Country	US
Kind code	B2
Filing date	Sep 30, 2022
Priority date	Sep 30, 2022
Publication date	Jul 15, 2025
Grant date	Jul 15, 2025

Abstract

A method for performing prefetching operations is disclosed. The method includes storing a recorded access pattern indicating a set of accesses for a region; in response to an access within the region, fetching the recorded access pattern; and performing prefetching based on the access pattern.

First claim

What is claimed is:

1. A method for performing prefetching operations, the method comprising:
in response to observing an access pattern to a first memory region, storing the access pattern as a recorded access pattern;
associating a region type with the recorded access pattern and associating the first memory region with the region type;
in response to observing a second access pattern in a second memory region, wherein the second access pattern has greater than zero and less than a threshold number of differences from the access pattern, associating the second memory region with the region type;
in response to an access within the first memory region, fetching the recorded access pattern for the region type, based on the associating of the first memory region with the region type; and
performing prefetching based on the access pattern.

2. The method of claim 1 , wherein associating the recorded access pattern with the region type includes selecting a hashing function that maps both a first memory region and a second memory region to the region type.

3. The method of claim 2 , wherein fetching the recorded access pattern is performed in response to identifying the region type based on a first region address of the first memory region.

4. The method of claim 2 , further comprising identifying the recorded access pattern based on a region type for the first memory region, the identifying comprising performing a lookup in a recorded pattern table that includes entries that map region types to recorded patterns.

5. The method of claim 1 , where performing prefetching based on the access pattern comprises prefetching region subdivisions specified by the access pattern.

6. The method of claim 1 , further comprising:
in response to a miss within the region, updating a pattern observation table based on the miss.

7. The method of claim 6 , wherein updating the pattern observation table includes, in response to no pattern observation existing for the region, generating a new pattern observation entry.

8. The method of claim 6 , wherein updating the pattern observation table includes setting an indication for a region subdivision associated with the miss, wherein the indication indicates that the region subdivision is to be prefetched.

9. The method of claim 6 , further comprising evicting a pattern observation entry to a recorded pattern table used for identifying the access pattern based on a region type of a first memory region.

10. The method of claim 1 , wherein the region type is associated with both a first memory region and a second memory region different than the first memory region.

11. A system for performing prefetching operations, the system comprising:
a memory; and
a prefetcher configured to:
in response to observing an access pattern to a first memory region, store the access pattern as a recorded access pattern;
associating a region type with the recorded access pattern and associating the first memory region with the region type;
in response to observing a second access pattern in a second memory region, wherein the second access pattern has greater than zero and less than a threshold number of differences from the access pattern, associate the second memory region with the region type;
in response to an access within the first memory region, fetch the recorded access pattern for the region type, based on the associating of the first memory region with the region type; and
performing prefetching into the memory based on the access pattern.

12. The system of claim 11 , wherein associating the recorded access pattern with the region type includes selecting a hashing function that maps both a first memory region and a second memory region to the region type.

13. The system of claim 12 , wherein fetching the recorded access pattern is performed in response to identifying the region type based on a first region address of the first memory region.

14. The system of claim 12 , further comprising identifying the recorded access pattern based on a region type for the first memory region, the identifying comprising performing a lookup in a recorded pattern table that includes entries that map region types to recorded patterns.

15. The system of claim 11 , where performing prefetching based on the access pattern comprises prefetching region subdivisions specified by the access pattern.

16. The system of claim 11 , wherein the prefetcher is further configured to:
in response to a miss within the region, update a pattern observation table based on the miss.

17. The system of claim 16 , wherein updating the pattern observation table includes, in response to no pattern observation existing for the region, generating a new pattern observation entry.

18. The system of claim 16 , wherein updating the pattern observation table includes setting an indication for a region subdivision associated with the miss, wherein the indication indicates that the region subdivision is to be prefetched.

19. The system of claim 16 , wherein the prefetcher is further configured to evict a pattern observation entry to a recorded pattern table used for identifying the access pattern based on a region type of a first memory region.

20. A system comprising:
a plurality of processing devices;
a cache configured to service requests for access to memory made by the plurality of processing devices; and
a prefetcher configured to:
in response to observing an access pattern to a first memory region, store the access pattern as a recorded access pattern;
associate a region type with the recorded access pattern and associate the first memory region with the region type;
in response to observing a second access pattern in a second memory region, wherein the second access pattern has greater than zero and less than a threshold number of differences from the access pattern, associate the second memory region with the region type;
in response to an access within the first memory region, fetch the recorded access pattern, based on the associating of the first memory region with the region type; and
performing prefetching into the cache based on the access pattern.

21. The system of claim 20 , wherein associating the recorded access pattern with the region type includes selecting a hashing function that maps both a first memory region and a second memory region to the region type.

Assignees

• Advanced Micro Devices Inc

Inventors

• Loh Gabriel H
• Scrbak Marko
• Arunkumar Akhil
• Kalamatianos John

Classifications

• G06F12/0877

  Cache access modes · CPC title

• G06F12/0811

  with multilevel cache hierarchies · CPC title

• G06F2212/502

  using adaptive policy · CPC title

• G06F12/0284

  Multiple user address space allocation, e.g. using different base addresses (interprocessor communication G06F15/163) · CPC title

• G06F2212/1008

  Correctness of operation, e.g. memory ordering · CPC title