Universal cache management system

Patent metadata

Field	Value
Publication number	US-11755481-B2
Application number	US-201816153610-A
Country	US
Kind code	B2
Filing date	Oct 5, 2018
Priority date	Feb 28, 2011
Publication date	Sep 12, 2023
Grant date	Sep 12, 2023

Abstract

Techniques for universal cache management are described. In an example embodiment, a plurality of caches are allocated, in volatile memory of a computing device, to a plurality of data-processing instances, where each one of the plurality of caches is exclusively allocated to a separate one of the plurality of data-processing instances. A common cache is allocated in the volatile memory of the computing device, where the common cache is shared by the plurality of data-processing instances. Each instance of the plurality of data-processing instances is configured to: identify a data block in the particular cache allocated to that instance, where the data block has not been changed since the data block was last persistently written to one or more storage devices; cause the data block to be stored in the common cache; and remove the data block from the particular cache. Data blocks in the common cache are maintained without being persistently written to the one or more storage devices.

First claim

What is claimed is:

1. A method comprising:
allocating, in a first random access memory (RAM) of a first computing device, a first cache exclusively to a first instance of two or more data-processing instances, wherein the first cache is configured to store copies of a first set of data blocks that are persistently stored on one or more storage devices, and wherein the allocating the first cache is performed, at least in part, by an operating system (OS) instance of the first computing devices;
allocating, in a second RAM of a second computing device, a second cache exclusively to a second instance of the two or more data-processing instances, wherein the second cache is configured to store copies of a second set of data blocks that are persistently stored on the one or more storage devices, and wherein the allocating the second cache is performed, at least in part, by an OS instance of the second computing device;
allocating at least a portion of a common cache in a third RAM of a third computing device;
the first instance performing:
identifying for eviction from the first cache a first data block at least because the first data block has not been changed since the first data block was last persistently written to the one or more storage devices;
in response to identifying for eviction from the first cache a first data block at least because the first data block has not been changed since the first data block was last persistently written to the one or more storage devices:
causing the first data block to be stored in the common cache, and
removing the first data block from the first cache;

the second instance performing:
identifying for eviction from the second cache a second data block at least because the second data block has not been changed since the second data block was last persistently written to the one or more storage devices:
in response to identifying for eviction from the second cache a second data block at least because the second data block has not been changed since the second data block was last persistently written to the one or more storage devices:
causing the second data block to be stored in the common cache, and
removing the second data block from the second cache;

maintaining data blocks, including the first data block and the second data block, in the common cache without persistently writing the data blocks to the one or more storage devices.

2. The method of claim 1 , wherein the two or more data-processing instances are two or more database instances that manage one or more databases that are stored on the one or more storage devices.

3. The method of claim 1 , further comprising:
in response to a first request for data from the first data block, the first instance retrieving the first data block from the common cache instead of the one or more storage devices, and storing the first data block back into the first cache; and
in response to a second request for data from the second data block, the second instance retrieving the second data block from the common cache instead of the one or more storage devices, and storing the second data block back into the second cache.

4. The method of claim 3 , wherein the first instance retrieving the first data block from the common cache includes sending a request for the first data block to the third computing device.

5. The method of claim 4 , further including:
maintaining a directory that maps block-identifying data of certain data blocks to the common cache, said certain data blocks being stored in the common cache;
before the first instance retrieving the first data block, said first instance uses the directory to determine the first data block is stored in said common cache.

6. The method of claim 1 , wherein said first RAM and said second RAM comprise volatile memory.

7. One or more non-transitory computer-readable media storing one or more sequences of one or more instructions which, when executed by one or more processors, cause:
allocating, in a first random access memory (RAM) of a first computing device, a first cache exclusively to a first instance of two or more data-processing instances, wherein the first cache is configured to store copies of a first set of data blocks that are persistently stored on one or more storage devices, and wherein the allocating the first cache is performed, at least in part, by an operating system (OS) instance of the first computing device;
allocating, in a second RAM of a second computing device, a second cache exclusively to a second instance of the two or more data-processing instances, wherein the second cache is configured to store copies of a second set of data blocks that are persistently stored on the one or more storage devices, and wherein the allocating the second cache is performed, at least in part, by an OS instance of the second computing device;
allocating at least a portion of a common cache in a third RAM of a third computing device;
the first instance performing:
identifying for eviction from the first cache a first data block at least because the first data block has not been changed since the first data block was last persistently written to the one or more storage devices;
in response to identifying for eviction from the first cache a first data block at least because the first data block has not been changed since the first data block was last persistently written to the one or more storage devices:
causing the first data block to be stored in the common cache, and removing the first data block from the first cache;

the second instance performing:
identifying for eviction from the second cache a second data block at least because the second data block has not been changed since the second data block was last persistently written to the one or more storage devices:
in response to identifying for eviction from the second cache a second data block at least because the second data block has not been changed since the second data block was last persistently written to the one or more storage devices:
causing the second data block to be stored in the common cache, and removing the second data block from the second cache;

maintaining data blocks, including the first data block and the second data block, in the common cache without persistently writing the data blocks to the one or more storage devices.

8. The one or more non-transitory computer-readable media of claim 7 , wherein the two or more data-processing instances are two or more database instances that manage one or more databases that are stored on the one or more storage devices.

9. The one or more non-transitory computer-readable media of claim 7 , wherein maintaining data blocks in the common cache comprises maintaining block-identifying data for each of the data blocks stored in the common cache.

10. The one or more non-transitory computer-readable media of claim 7 , wherein the one or more sequences of instructions include instructions that, when executed by said one or more processors, cause:
in response to a first request for data from the first data block, the first instance retrieving the first data block from the common cache instead of the one or more storage devices, and storing the first data block back into the first cache; and
in response to a second request for data from the second data block, the second instance retrieving the second data block from the common cache instead of the one or more storage devices, and storing the second data block back into the second cache.

11. The one or more non-transitory computer-readable media of claim 10 , wherein the first instance retrieving the first data block from the common cache includes sending a request f

Assignees

• Oracle Int Corp

Inventors

• Bagal Prasad V
• Long Rich

Classifications

• G06F12/0811 Primary

  with multilevel cache hierarchies · CPC title

• G06F16/24552

  Database cache management · CPC title

• G06F12/084

  with a shared cache · CPC title

• G06F12/0897

  with two or more cache hierarchy levels (with multilevel cache hierarchies G06F12/0811) · CPC title

• G06F2212/22

  Employing cache memory using specific memory technology · CPC title