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From Michael Dürig (JIRA) <j...@apache.org>
Subject [jira] [Created] (OAK-5278) Improved compaction estimator
Date Mon, 12 Dec 2016 15:49:58 GMT
Michael Dürig created OAK-5278:
----------------------------------

             Summary: Improved compaction estimator
                 Key: OAK-5278
                 URL: https://issues.apache.org/jira/browse/OAK-5278
             Project: Jackrabbit Oak
          Issue Type: Improvement
          Components: segment-tar
            Reporter: Michael Dürig
             Fix For: 1.8


OAK-4293 introduced a new approach for estimating whether we actually want to run or skip
a gc cycle. That approach is purely based on the absolute growth of the repository's on disk
footprint. 

I think this can be further refined as with the {{GCJournal}} we can effectively extrapolate
the amount of garbage at a given point in time given the history of previous gc cycles. E.g.
let {{S_n}} be the size of the repository and {{G_n}} the percentage of garbage right before
the {{n}}-th gc cycle. We can then linearly extrapolate the garbage {{G_n+1}} for the {{n+1}}-the
gc cycle along the repository sizes:

{code}
G_n+1 = G_n * (S_k+1 - S_k)/(S_k - S_k-1)
{code}




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