[jira] [Updated] (IGNITE-5875) Implement memory metric that will signal about uneven distribution of pages between segments of durable memory

["Vladimir Ozerov (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IGNITE-5875?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Vladimir Ozerov updated IGNITE-5875:
------------------------------------
    Fix Version/s:     (was: 2.3)

> Implement memory metric that will signal about uneven distribution of pages between segments of durable memory
> --------------------------------------------------------------------------------------------------------------
>
>                 Key: IGNITE-5875
>                 URL: https://issues.apache.org/jira/browse/IGNITE-5875
>             Project: Ignite
>          Issue Type: Improvement
>          Components: persistence
>    Affects Versions: 2.1
>            Reporter: Ivan Rakov
>
> When persistence is enabled, we split memory policy into K equal segments (K = concurrency level). We calculate hash of pageId to determine segment where page will be stored.
> Pages eviction to disk starts when segment is full. If hash function is bad enough, one segment can overflow when there are lots of free space, and evictions can start too early. We want to be able to distinguish such situations. 
> Proposed name for metrics: pageHashFunctionScore
> Proposed formula: difference between maximum and minimum percentage of segment fill



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