Memory allocation buffer for reduction of heap fragmentation

• US 9,128,949 B2
• Filed: 01/18/2013
• Issued: 09/08/2015
• Est. Priority Date: 01/18/2012
• Status: Active Grant

• Current Assignee: Cloudera Incorporated
• Original Assignee: Cloudera Incorporated
• Inventors: Lipcon, Todd
• Primary Examiner(s): MORRISON, JAY A
• Application Number:
  US13/745,461
• Publication Number:
  US 20130185337A1
• Time in Patent Office: 963 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G06F 12/0808 with cache invalidating means G06F12/0815 takes precedence
• CPC Class Codes: G06F 12/12 Replacement control
• CPC Class Codes: G06F 12/128 adapted to multidimensional cache systems, e.g. set-associative, multicache, multiset or multilevel
• CPC Class Codes: G06F 16/1727 Details of free space management performed by the file system saving storage space on storage systems G06F3/0608; management of blocks in storage devices G06F3/064
• CPC Class Codes: G06F 2212/1044 Space efficiency improvement
• CPC Class Codes: G06F 3/0611 in relation to response time
• CPC Class Codes: G06F 3/0631 by allocating resources to storage systems
• CPC Class Codes: G06F 3/0644 Management of space entities, e.g. partitions, extents, pools
• CPC Class Codes: G06F 3/0652 Erasing, e.g. deleting, data cleaning, moving of data to a wastebasket
• CPC Class Codes: G06F 3/067 Distributed or networked storage systems, e.g. storage area networks [SAN], network attached storage [NAS]
• CPC Class Codes: G06F 3/0683 Plurality of storage devices
• CPC Class Codes: H04L 67/1097 for distributed storage of data in networks, e.g. transport arrangements for network file system [NFS], storage area networks [SAN] or network attached storage [NAS]

Abstract

Systems and methods of a memory allocation buffer to reduce heap fragmentation. In one embodiment, the memory allocation buffer structures a memory arena dedicated to a target region that is one of a plurality of regions in a server in a database cluster such as an HBase cluster. The memory area has a chunk size (e.g., 2 MB) and an offset pointer. Data objects in write requests targeted to the region are received and inserted to the memory arena at a location specified by the offset pointer. When the memory arena is filled, a new one is allocated. When a MemStore of the target region is flushed, the entire memory arenas for the target region are freed up. This reduces heap fragmentation that is responsible for long and/or frequent garbage collection pauses.

Claims

1. A method for reducing overall delays caused by garbage collection processes due to memory fragmentation in a region server hosting a plurality of regions for a distributed database system, the region server maintaining a heap in the region server'"'"'s memory, the method comprising:

implementing, at the region server, an in-memory store for each region, wherein the in-memory store for each region is to hod data to be written until the data reaches a predetermined size and flush the data to a storage when the predetermined size is reached;

receiving a write request from a client, wherein the write request includes a target region and an data object for insertion into the target region;

creating, in the heap, a memory arena dedicated to the target region by allocating one space of a select size in the heap; and

storing the data object in a space in the memory arena at a location that is continued from a previous location such that, when an in-memory store for the target region flushes the data it holds, the space freed from the memory arena dedicated to the target region is contiguous.

2. The method of claim 1, further comprising:

storing the object at a location specified by an offset pointer in the allocated space; and

incrementing the offset pointer by the length of the object stored.

3. The method of claim 2, wherein reservation of storage in the allocated space proceeds without the use of mutual exclusion locks.

4. The method of claim 2, wherein an atomic compare-and-swap (CAS) instruction increments the offset pointer without other coordination between processors.

5. The method of claim 2, wherein the distributed database system is a HBase cluster.

6. The method of claim 5, wherein the target region is one of a plurality of regions hosted on a region server in the HBase cluster.

7. The method of claim 6, wherein a memory arena for each of the plurality of regions including the target region is periodically flushed when usage of the memory arena exceeds or reaches a threshold.

8. The method of claim 7, wherein when the memory arena is flushed, memory fragmentation is reduced.

9. The method of claim 1, wherein the structuring is performed by a local allocation buffer to keep objects from a plurality of regions including the target region from intermingling in memory.

10. The method of claim 2, further comprising:

receiving a new object for insertion into the target region;

determining that there is insufficient or no free space in the memory arena;

structuring a new memory arena dedicated to the target region;

allocating space for the new object from the new memory arena;

storing the new object at a location specified by an offset pointer that is set to zero in the allocated space; and

incrementing the offset pointer by the length of the new object.

11. The method of claim 1, wherein each memory arena has a size of or near 0.5 MB, 1 MB, 2 MB, 4 MB, or 8 MB.

12. A non-transitory machine-readable storage medium including executable instructions, which when executed by a processor, cause the processor to:

implement, at a server hosting a plurality of regions for a distributed database system and maintaining a heap in the server'"'"'s memory, an in-memory store for each region, wherein the in-memory store for each region is to hold data to be written until the data reaches a predetermined size and to flush the data to a storage when the predetermined size is reached;

receive a write request from a client, wherein the write request includes a target region and an data object for insertion into the target region;

create, in the heap, a memory arena dedicated to the target region by allocating one space of a select size in the heap; and

store the data object in a space in the memory arena at a location that is continued from a previous location such that, when an in-memory store for the target region flushes the data it holds, the space freed from the memory arena dedicated to the target region is contiguous.

13. The medium of claim 12, wherein the server is one of a plurality of server in a distributed HBase cluster.

14. A server hosting a plurality of regions for a distributed database system, the server maintaining a heap in a memory of the server, the server'"'"'s memory including instructions which, upon executed by a processor of the server, instruct the server to perform:

implementing, at the server, an in-memory store for each region, wherein the in-memory store for each region is to hold data to be written until the data reaches a predetermined size and to flush the data to a storage when the predetermined size is reached;

receiving a write request from a client, wherein the write request includes a target region and an data object for insertion into the target region;

creating, in the heap, a memory arena dedicated to the target region by allocating one space of a select size in the heap; and

storing the data object in a space in the memory arena at a location that is continued from a previous location such that, when an in-memory store for the target region flushes the data it holds, the space freed from the memory arena dedicated to the target region is contiguous.

15. A method for reducing overall delays caused by garbage collection processes due to memory fragmentation in a region server hosting a plurality of regions for a distributed database system, the region server maintaining a heap in the region server'"'"'s memory, the method comprising:

implementing, at the region server, an in-memory store for each region, wherein the in-memory store for each region is to hold data to be written until the data reaches a predetermined size and to flush the data to a storage when the predetermined size is reached;

receiving a write request from a client, wherein the write request includes a target region and an data object for insertion into the target region;

locating, in the heap, a memory arena dedicated to the target region;

determining that the memory arena has enough space for the data object; and

storing the data object in a space in the memory arena at a location that is continued from a previous location such that, when an in-memory store for the target region flushes the data it holds, the space freed from the memory arena dedicated to the target region is contiguous.

16. A non-transitory machine-readable storage medium including executable instructions, which when executed by a processor, cause the processor to:

implement, at a server hosting a plurality of regions for a distributed database system, an in-memory store for each region, wherein the in-memory store for each region is to hold data to be written until the data reaches a predetermined size and to flush the data to a storage when the predetermined size is reached;

receive a write request from a client, wherein the write request includes a target region and an data object for insertion into the target region;

locate, in a heap maintained in the server'"'"'s memory, a memory arena dedicated to the target region;

determine that the memory arena has enough space for the data object; and

store the data object in a space in the memory arena at a location that is continued from a previous location such that, when an in-memory store for the target region flushes the data it holds, the space freed from the memory arena dedicated to the target region is contiguous.

17. A server hosting a plurality of regions for a distributed database system, the server maintaining a heap in a memory of the server, the server'"'"'s memory including instructions which, upon executed by a processor of the server, instruct the server to perform:

implementing, at the server, an in-memory store for each region, wherein the in-memory store for each region is to hold data to be written until the data reaches a predetermined size and to flush the data to a storage when the predetermined size is reached;

receiving a write request from a client, wherein the write request includes a target region and an data object for insertion into the target region;

locating, in the heap, a memory arena dedicated to the target region;

determining that the memory arena has enough space for the data object; and

storing the data object in a space in the memory arena at a location that is continued from a previous location such that, when an in-memory store for the target region flushes the data it holds, the space freed from the memory arena dedicated to the target region is contiguous.