[jira] [Assigned] (FLINK-12699) Reduce CPU consumption when snapshot/restore the spilled key-group

["Yu Li (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-12699?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Yu Li reassigned FLINK-12699:
-----------------------------

    Assignee: PengFei Li  (was: Yu Li)

> Reduce CPU consumption when snapshot/restore the spilled key-group
> ------------------------------------------------------------------
>
>                 Key: FLINK-12699
>                 URL: https://issues.apache.org/jira/browse/FLINK-12699
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Runtime / State Backends
>            Reporter: Yu Li
>            Assignee: PengFei Li
>            Priority: Major
>
> We need to prevent the unnecessary de/serialization when snapshotting/restoring the spilled state key-group. To achieve this, we need to:
> 1. Add meta information for {{HeapKeyedStatebackend}} checkpoint on DFS, separating the on-heap and on-disk part
> 2. Write the off-heap bytes directly to DFS when checkpointing and mark it as on-disk
> 3. Directly write the bytes onto disk when restoring the data back from DFS, if it's marked as on-disk
> Notice that we cannot directly use file copy since we use mmap meanwhile support copy-on-write.



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