Note: This bug is displayed in read-only format because the product is no longer active in Red Hat Bugzilla.

Bug 1096727

Summary: SingleFileStore can optimize space usage by coalescing adjacent free entry blocks
Product: [JBoss] JBoss Data Grid 6 Reporter: Dan Berindei <dberinde>
Component: InfinispanAssignee: Tristan Tarrant <ttarrant>
Status: CLOSED CURRENTRELEASE QA Contact: Martin Gencur <mgencur>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 6.2.0CC: afield, jdg-bugs
Target Milestone: ER2   
Target Release: 6.3.0   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2015-01-26 14:03:17 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description Dan Berindei 2014-05-12 10:48:12 UTC 
This issue is related to bug 1096726 (issue ISPN-3877).

Here we have a use case where the size of the entries gradually keeps on increasing and then finally those entries expire.
1. Smaller entries expire and new bigger entries start getting added
2. These new bigger entries will not fit into the free slots (entries) created due to the expiry of smaller entries.
3. Thus, these new bigger entries only get allocated at the end of the file resulting in growth of file size.

The optimization proposed is to:
1. Coalesce/Combine adjacent free entries during the periodic purge cycle to create bigger/larger free entries.
2. While allocating from an existing free entry, check if the size of the free entry is more than required for the new request being allocated. If yes, then, split the free entry into two free entries:
a. First part equal to the length being requested
This is returned as a part of the allocation activity.
b. Second part equal to the remainder of the space.
This added back as a free entry to the freeList.

Thus free space created due to expiry of smaller entries becomes available for consumption for the larger entries to some extent.
This reduces file size of the store.
Comment 2 Alan Field 2014-05-23 16:02:19 UTC 
Verified with JDG 6.3.0 ER5