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From "Thomas Steinmaurer (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-13929) BTree$Builder / io.netty.util.Recycler$Stack leaking memory
Date Wed, 04 Oct 2017 06:12:00 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-13929?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16190865#comment-16190865
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Thomas Steinmaurer commented on CASSANDRA-13929:
------------------------------------------------

Ok, if this sort of caching is entirely only useful during streaming, this somehow explains
why I do not see any difference between the nodes here, cause they process regular business
and no repair, bootstrapping etc, thus I can't comment on the performance gain with the cache
(possibly this has been tested in CASSANDRA-9766 anyway).

If the cache is useful for streaming, it still would definitely make sense IMHO, to make the
max capacity configurable via a system property, cassandra.yaml or whatever place is preferred
here, cause ~ 1,8G heap usage for this sort of cache at -XmX8G does not make sense.

> BTree$Builder / io.netty.util.Recycler$Stack leaking memory
> -----------------------------------------------------------
>
>                 Key: CASSANDRA-13929
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-13929
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>            Reporter: Thomas Steinmaurer
>         Attachments: cassandra_3.11.0_min_memory_utilization.jpg, cassandra_3.11.1_mat_dominator_classes_FIXED.png,
cassandra_3.11.1_mat_dominator_classes.png, cassandra_3.11.1_snapshot_heaputilization.png
>
>
> Different to CASSANDRA-13754, there seems to be another memory leak in 3.11.0+ in BTree$Builder
/ io.netty.util.Recycler$Stack.
> * heap utilization increase after upgrading to 3.11.0 => cassandra_3.11.0_min_memory_utilization.jpg
> * No difference after upgrading to 3.11.1 (snapshot build) => cassandra_3.11.1_snapshot_heaputilization.png;
thus most likely after fixing CASSANDRA-13754, more visible now
> * MAT shows io.netty.util.Recycler$Stack as top contributing class => cassandra_3.11.1_mat_dominator_classes.png
> * With -Xmx8G (CMS) and our load pattern, we have to do a rolling restart after ~ 72
hours
> Verified the following fix, namely explicitly unreferencing the _recycleHandle_ member
(making it non-final). In _org.apache.cassandra.utils.btree.BTree.Builder.recycle()_
> {code}
>         public void recycle()
>         {
>             if (recycleHandle != null)
>             {
>                 this.cleanup();
>                 builderRecycler.recycle(this, recycleHandle);
>                 recycleHandle = null; // ADDED
>             }
>         }
> {code}
> Patched a single node in our loadtest cluster with this change and after ~ 10 hours uptime,
no sign of the previously offending class in MAT anymore => cassandra_3.11.1_mat_dominator_classes_FIXED.png
> Can' say if this has any other side effects etc., but I doubt.



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