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https://issues.apache.org/jira/browse/JENA-801?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14210093#comment-14210093
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Simon Helsen commented on JENA-801:
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Bala, when running in memory mapped I/O, you need to *reduce* the Java heap
because allocations will happen in the native heap of the app (which is
controlled by the OS and outside the -Xmx). If there isn't enough native heap,
you will run into an OOME as well and it may not be immediately apparent from
the exception that the OOME was caused by native heap exhaustion.
> When the server is under load, many queries are piling up and seems to be in
> some kind of dead lock.
> ----------------------------------------------------------------------------------------------------
>
> Key: JENA-801
> URL: https://issues.apache.org/jira/browse/JENA-801
> Project: Apache Jena
> Issue Type: Bug
> Components: TDB
> Affects Versions: TDB 0.9.4, Jena 2.11.2
> Reporter: Bala Kolla
> Attachments:
> ThreadLocksInBlockMgrJournalAfterGuavaCacheInNodeTable.htm,
> TracesWithManyItersOfBlockMgrJournal_Valid_Method.txt,
> TracesWithManyItersOfBlockMgrJournal_getRead_Method.txt,
> WAITDataReportShowingTheLockContention.zip,
> WAITDataReportShowingTheLockContentionWithoutQueryFilter.zip
>
>
> We were testing our server with repositories of varied sizes and in almost
> all the cases when the server peaks its capacity (of maximum number of users
> it can support), It seems like the queries are piling up because of the lock
> contention in NodeTableCache.
> Here are some details about the repository..
> size of indices on disk - 150GB
> type of hard disk used - SSD and HDD with high RAM (seeing the same result in
> both the cases)
> OS - Linux
> Details on the user load;
> We are trying to simulate a very active user load where all the users are
> executing many usecases that would result in many queries and updates on TDB.
> I would like to know what are the possible solutions to work around and avoid
> this situation. I am thinking of the following, please let me know if there
> is any other way to work around this bottleneck.
> Control the updates to the triple store so that we only do it when there are
> not many queries pending. We would have to experiment how this impact the
> usecases..
> Is there any other way to make this lock contention go away? Can we have
> multiple instances of this cache? For example many (90%) of our queries are
> executed with a query scope (per project). So, can we have a separate
> NodeTable cache for each query scope (project in our case) and one for
> global?
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