[jira] [Updated] (BEAM-11707) Optimize WindmillStateCache CPU usage

["Sam Whittle (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/BEAM-11707?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Sam Whittle updated BEAM-11707:
-------------------------------
    Resolution: Fixed
        Status: Resolved  (was: Open)

> Optimize WindmillStateCache CPU usage
> -------------------------------------
>
>                 Key: BEAM-11707
>                 URL: https://issues.apache.org/jira/browse/BEAM-11707
>             Project: Beam
>          Issue Type: Bug
>          Components: runner-dataflow
>            Reporter: Sam Whittle
>            Assignee: Sam Whittle
>            Priority: P2
>          Time Spent: 2h 50m
>  Remaining Estimate: 0h
>
> From profiling nexmark Query11 which has many unique tags per key, I observed that the WindmillStateCache cpu usage was 6% of CPU.
> The usage appears to be due to the invalidation set maintenance as well as many reads/inserts.
> The invalidation set is maintained so that if a key encounters an error processing or the cache token changes, we can invalidate all the entries for a key.  Currently this is done by removing all entries for the key from the cache.  Another alternative which appears much more CPU efficient is to instead leave the entries in the cache but make them unreachable.  This can be done by having a per-key object that uses object equality as part of the cache lookup.  Then to discard entries for the key, we start using a new per-key object.  Cleanup of per-key objects can be done with a weak reference map.
> Another cost to the cache is that objects are grouped by window so that they are kept/evicted all at once.  However currently when reading items into the cache, we fetch the window set and then lookup each tag in it.  This could be cached for the key to avoid multiple cache lookups. Similarly for putting objects we lookup and insert each tag separately and then update the cache to update the weight for the per-window set.  This could be done once after all updates for the window have been made.



--
This message was sent by Atlassian Jira
(v8.3.4#803005)