[teiid-issues] [JBoss JIRA] (TEIID-2404) Expose buffermanager monitoring properties

[Steven Hawkins (JIRA)]

    [ https://issues.jboss.org/browse/TEIID-2404?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12756193#comment-12756193 ] 

Steven Hawkins commented on TEIID-2404:
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4) maxReserveBytes is a working measure of how much space is left over out of the initial maxReserveKB setting after accounting for soft memory references (which aren't counted toward the activeBatchBytes) and batch overhead.

So the "Amount of Memory" we believe to be in use by the buffermanager object hard/soft references (not including the memory buffer / disk) is:
activBatchBytes + (initial maxReserveBytes) - maxReserveBytes

However we would need to add a reference to the initial maxReserveBytes setting to compute this.

reserveBatchBytes is the amount of available space (out of the initial maxReserveKB) to be reserved by running plans.  This value can drop below zero as plans can force memory reservations beyond the max.  So the "amount of memory that plans have requested" is:
(initial maxReserveBytes) - reserveBatchBytes 

The object/batches represented by reserveBatchBytes may (potentially as a weak or soft reference) or may not be held by the buffermanager.

> I do not think I understand what it means by "BufferFrontedCacheStore concurrent bits set X block size."

There are ConcurrentBitSet's that track the blocks of memory in use.  There's one for blocks and one for inodes (which is mostly negligible).  So the amount of the memory buffer currently in use would be:
blocksInUse.getBitsSet() * BLOCK_SIZE 

where the memory block size is currently fixed at 8KB.

                
> Expose buffermanager monitoring properties
> ------------------------------------------
>
>                 Key: TEIID-2404
>                 URL: https://issues.jboss.org/browse/TEIID-2404
>             Project: Teiid
>          Issue Type: Feature Request
>          Components: Server
>    Affects Versions: 8.3
>            Reporter: Steven Hawkins
>            Assignee: Ramesh Reddy
>             Fix For: 8.3
>
>
> We should expose:
> BufferServiceImpl.getUserBufferSpace - the number of megs currently used by the buffermanager disk storage.
> A rough total of the memory buffer space used can be added, which would be from the BufferFrontedCacheStore concurrent bits set X block size.
> Also the BufferManagerImpl could report the total estimate of objects held in memory.

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