[jira] [Commented] (OAK-2193) No garbage collection after reaching generation z

["Alex Parvulescu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/OAK-2193?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14171088#comment-14171088 ] 

Alex Parvulescu commented on OAK-2193:
--------------------------------------

we also have to take into consideration is GC is even practical after the 'z'th generation. 
at each cleanup we reclaim at least 1/4 of garbage, leaving max 3/4 of the file size: as 'z' is the 26th letter, so 3/4 raised to the 25th power is 0.00075 [0], leaving a file size that is at max 256mb x 0.00075 = 350k. 
is the extra effort worth it? :)

[0] http://www.wolframalpha.com/input/?i=0.75+to+the+25th+power

> No garbage collection after reaching generation z
> -------------------------------------------------
>
>                 Key: OAK-2193
>                 URL: https://issues.apache.org/jira/browse/OAK-2193
>             Project: Jackrabbit Oak
>          Issue Type: Bug
>          Components: core
>            Reporter: Michael Dürig
>            Assignee: Michael Dürig
>         Attachments: OAK-2193.patch
>
>
> Tar garbage collection generates new generation of tar files once it determines a given file contains garbage. New generations will have the next lower case letter from the alphabet appended to its file name. When the letter 'z' is reached, no further garbage collection is done. 
> I think we need to fix this as otherwise garbage collection just stops working arbitrarily. 



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