[jira] [Commented] (OAK-4281) Rework memory estimation for compaction

["Michael Dürig (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OAK-4281?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15280270#comment-15280270 ] 

Michael Dürig commented on OAK-4281:
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One good alternative where we could derive the delta value from is the node deduplication cache ({{RecordCache.DeduplicationCache}}): compaction [instantiates a new generation | https://github.com/apache/jackrabbit-oak/blob/0047f257c2aed16fc38a98f9d8e758991a70f6cd/oak-segment-tar/src/main/java/org/apache/jackrabbit/oak/segment/file/FileStore.java#L1066] of that cache. The memory requirements of the previous (that is, current) generation of this cache should be a good estimate of the extra memory required to run compaction. 

> Rework memory estimation for compaction
> ---------------------------------------
>
>                 Key: OAK-4281
>                 URL: https://issues.apache.org/jira/browse/OAK-4281
>             Project: Jackrabbit Oak
>          Issue Type: Task
>          Components: segment-tar
>            Reporter: Michael Dürig
>            Assignee: Alex Parvulescu
>              Labels: compaction, gc
>             Fix For: 1.6
>
>
> As a result of OAK-3348 we need to partially rework the memory estimation step done for deciding whether compaction can run or not. In {{oak-segment}} there was a {{delta}} value derived from the compaction map. As the latter is gone in {{oak-segment-next}} we need to decide whether there is another way to derive this delta or whether we want to drop it entirely. 



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