Synchronization of metadata in a multi-threaded system

• US 9,589,039 B2
• Filed: 12/13/2012
• Issued: 03/07/2017
• Est. Priority Date: 12/13/2012
• Status: Active Grant

• Current Assignee: Sybase Incorporated (SAP SE)
• Original Assignee: Sybase Incorporated (SAP SE)
• Inventors: Pathak, Amit, Kelkar, Aditya, Rathod, Paresh
• Primary Examiner(s): ASPINWALL, EVAN S
• Application Number:
  US13/713,212
• Publication Number:
  US 20140172790A1
• Time in Patent Office: 1,545 Days
• Field of Search: 707/613, 707/638, 707/704, 707/610
• US Class Current: 1/1
• CPC Class Codes: G06F 16/27 Replication, distribution or synchronisation of data between databases or within a distributed database system; Distributed database system architectures therefor

Abstract

Synchronization of metadata structures in a multi-threaded system includes receiving, by a first thread of a processing device, a request for a metadata structure located in a first cache associated with an object, obtaining, by the first thread of the processing device, a synchronization mechanism associated with the first cache, holding, by the first thread of the processing device, the metadata structure associated with the object, receiving, by a second thread of the processing device, a request for the metadata structure in a second cache associated with the object, obtaining, by the second thread of the processing device, a synchronization mechanism associated with the second cache and informing the second thread of the processing device that the metadata structure associated with the object is not available.

Claims

1. A method, comprising:

receiving, by a first thread of a processing device, a request for a metadata structure located in a first cache associated with an object;

accessing, by the first thread of the processing device, the first cache based upon a state of a synchronization mechanism associated with the first cache;

comparing, by the first thread of the processing device, wherein comparing comprises;

performing a comparison of the metadata structure to a value associated with the metadata structure, and

holding, by the first thread of the processing device, the metadata structure associated with the object;

operating, by the first thread of the processing device, on the metadata structure based upon the comparison of the metadata structure to the value;

receiving, by a second thread of the processing device, a request for the metadata structure in a second cache associated with the object;

accessing, by the second thread of the processing device, the second cache based upon a state of a synchronization mechanism associated with the second cache; and

operating, by the second thread of the processing device, on the metadata structure after the first thread ceases holding the requested metadata structure.

2. The method of claim 1, further comprising:

reserving, by the first thread of the processing device, the metadata structure associated with the object.

3. The method of claim 1, further comprising:

unreserving, by the first thread of the processing device, the metadata structure associated with the object.

4. The method of claim 1, further comprising:

upholding, by the first thread of the processing device, the metadata structure associated with the object.

5. The method of claim 1, wherein the request for the metadata structure in a second cache associated with the object further comprises a request to evict the metadata structure associated with the object.

6. The method of claim 5, further comprising:

selecting, by the second thread of the processing device, a metadata structure in the second cache not associated with the object to be evicted.

7. The method of claim 6, further comprising:

allocating, by the second thread of the processing device, a new metadata structure based on memory previously used by the metadata structure in the second cache not associated with the object;

initializing, by the second thread of the processing device, a new metadata structure using the memory previously used by the metadata structure in the second cache not associated with the object;

accessing, by the second thread of the processing device, a third cache based upon a state of a synchronization mechanism associated with the third cache;

storing the new metadata structure in the third cache and releasing the synchronization mechanism associated with the third cache; and

accessing, by the second thread of the processing device, the second cache based upon the state of the synchronization mechanism associated with the second cache, storing the new metadata structure in the second cache and releasing the synchronization mechanism associated with the second cache.

8. The method of claim 1, further comprising

accessing, by the first thread of the processing device, a pool based upon a state of a synchronization mechanism associated with the pool;

initializing, by the first thread of the processing device, a new metadata structure in the pool; and

storing the initialized new metadata in the first cache and the second cache.

9. The method of claim 1, further comprising:

traversing, by the first thread of the processing device, a set of metadata structures stored in the first cache to identify a metadata structure associated with the object; and

traversing, by the second thread of the processing device, a set of metadata structures stored in the second cache to identify a metadata structure associated with the object.

10. The method of claim 1, further comprising:

holding, by the second thread of the processing device, the requested metadata structure associated with the object when the first thread ceases holding the requested metadata structure.

11. The method of claim 1, wherein the value associated with the metadata structure comprises a set value of the metadata structure.

12. The method of claim 1, wherein holding, by the first thread of the processing device, the metadata structure associated with the object limits operations performed on the metadata structure to the first thread of the processing device.

13. A system having a multi-threaded processing device sharing a metadata cache, comprising:

a plurality of object local caches configured to store metadata structures;

a global cache configured to store copies of each of the metadata structures;

a first thread of the processing device configured to;

receive a request for a metadata structure located in a first local cache associated with an object;

access the first local cache based upon a state of a synchronization mechanism associated with the first local cache;

compare the metadata structure, wherein comparing the metadata structure comprises;

performing a comparison of the metadata structure to a value associated with the metadata structure, and

holding the metadata structure associated with the object; and

operate on the metadata structure based upon the comparison of the metadata structure to the value; and

a second thread of the processing device configured to;

receive a request for the metadata structure in the global cache associated with the object;

access the global cache based upon a state of a synchronization mechanism associated with the global cache; and

operate on the metadata structure after the first thread ceases holding the requested metadata structure.

14. The system of claim 13, the first thread of the processing device further configured to reserve the metadata structure associated with the object and located in the first object local cache.

15. The system of claim 13, the first thread of the processing device further configured to unreserve the metadata structure associated with the object and located in the first object local cache.

16. The system of claim 13, the first thread of the processing device further configured to unhold the metadata structure associated with the object and located in the first object local cache.

17. The system of claim 13, wherein the request for the metadata structure associated with the object and located in the global cache further comprises a request to evict the metadata structure associated with the object.

18. The system of claim 17, the second thread of the processing device further configured to select a metadata structure not associated with the object and located in the global cache to be evicted.

19. The system of claim 18, the second thread of the processing device further configured to allocate a new metadata structure based on memory previously used by the metadata structure not associated with the object, initialize a new metadata structure using the memory previously used by the metadata structure not associated with the object, access a second object local cache based upon a state of a synchronization mechanism associated with the second object local cache, store the new metadata structure in the second object local cache and release the synchronization mechanism associated with the second object local cache, and access the second cache based upon the state of the synchronization mechanism associated with the global cache, store the new metadata structure in the global cache and release the synchronization mechanism associated with the global cache.

20. The system having a multi-threaded processing device sharing a metadata cache, of claim 13, further comprising:

a first thread of the processing device further configured to;

traverse a set of metadata structures stored in the first local cache to identify a metadata structure associated with the object; and

a second thread of the processing device further configured to;

traverse a set of metadata structures stored in the global cache to identify a metadata structure associated with the object.

21. The system having a multi-threaded processing device sharing a metadata cache, of claim 13, further comprising:

a second thread of the processing device further configured to;

hold the requested metadata structure associated with the object when the first thread ceases holding the requested metadata structure.

22. The system of claim 13, wherein the value associated with the metadata structure comprises a set value of the metadata structure.

23. The system of claim 13, wherein holding, the metadata structure associated with the object limits operations performed on the metadata structure to the first thread of the processing device.

24. A non-transitory computer-readable medium having instructions stored thereon, the instructions causing at least one computing device to perform operations, the operations comprising:

receiving, by a first thread of a processing device, a request for a metadata structure located in a first cache associated with an object;

accessing, by the first thread of the processing device, the first cache based upon a state of a synchronization mechanism associated with the first cache;

comparing, by the first thread of the processing device, wherein comparing comprises;

performing a comparison of the metadata structure to a value associated with the metadata structure, and

holding, by the first thread of the processing device, the metadata structure associated with the object;

operating, by the first thread of the processing device, on the metadata structure based upon the comparison of the metadata structure to the value;

receiving, by a second thread of the processing device, a request for the metadata structure in a second cache associated with the object;

accessing, by the second thread of the processing device, the second cache based upon a state of a synchronization mechanism associated with the second cache; and

operating, by the second thread of the processing device, on the metadata structure after the first thread ceases holding the requested metadata structure.

25. The non-transitory computer-readable medium of claim 24, wherein the request for the metadata structure in a second cache associated with the object further comprises a request to evict the metadata structure associated with the object.

26. The non-transitory computer-readable medium of claim 25, the operations further comprising:

selecting, by the second thread of the processing device, a metadata structure in the second cache not associated with the object to be evicted.

27. The non-transitory computer-readable medium of claim 26, the operations further comprising:

allocating, by the second thread of the processing device, a new metadata structure based on memory previously used by the metadata structure in the second cache not associated with the object;

initializing, by the second thread of the processing device, a new metadata structure using the memory previously used by the metadata structure in the second cache not associated with the object;

accessing, by the second thread of the processing device, a third cache based upon a state of a synchronization mechanism associated with the third cache, storing the new metadata structure in the third cache and releasing the synchronization mechanism associated with the third cache; and

accessing, by the second thread of the processing device, the second cache based upon a state of the synchronization mechanism associated with the second cache, storing the new metadata structure in the second cache and releasing the synchronization mechanism associated with the second cache.

28. The non-transitory computer-readable medium of claim 24, the operations further comprising:

accessing, by the first thread of the processing device, a pool based upon a state of a synchronization mechanism associated with the pool;

initializing, by the first thread of the processing device, a new metadata structure in the pool; and

storing the initialized new metadata in the first cache and the second cache.

29. The non-transitory computer-readable medium of claim 24, the operations further comprising:

traversing, by the first thread of the processing device, a set of metadata structures stored in the first cache to identify a metadata structure associated with the object; and

traversing, by the second thread of the processing device, a set of metadata structures stored in the second cache to identify a metadata structure associated with the object.

30. The non-transitory computer-readable medium of claim 24, the operations further comprising:

holding, by the second thread of the processing device, the requested metadata structure associated with the object when the first thread ceases holding the requested metadata structure.

31. The non-transitory computer-readable medium of claim 24, wherein the value associated with the metadata structure comprises a set value of the metadata structure.

32. The non-transitory computer-readable medium of claim 24, wherein holding, by the first thread of the processing device, the metadata structure associated with the object limits operations performed on the metadata structure to the first thread of the processing device.