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https://issues.apache.org/jira/browse/LUCENE-2324?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12981895#action_12981895
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Jason Rutherglen commented on LUCENE-2324:
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Also, why are we always (well, likely) assigning the DWPT to a different thread
state if tryLock returns false? If there's a lot of contention (eg, far more
incoming threads than DWPTs), then won't the thread assignation code become a
hotspot?
In ThreadAffinityDocumentsWriterThreadPool.clearThreadBindings(ThreadState
perThread) we're actually clearing the entire map. When this's called in
IW.flush (which is unsynced on IW), if there are multiple concurrent flushes,
then perhaps a single DWPT is in use by multiple threads. To safeguard against
this and perhaps more easily add an assertion, maybe we should lock on the DWPT
rather than ThreadState?
> Per thread DocumentsWriters that write their own private segments
> -----------------------------------------------------------------
>
> Key: LUCENE-2324
> URL: https://issues.apache.org/jira/browse/LUCENE-2324
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Index
> Reporter: Michael Busch
> Assignee: Michael Busch
> Priority: Minor
> Fix For: Realtime Branch
>
> Attachments: LUCENE-2324-SMALL.patch, LUCENE-2324-SMALL.patch,
> LUCENE-2324-SMALL.patch, LUCENE-2324-SMALL.patch, LUCENE-2324-SMALL.patch,
> lucene-2324.patch, lucene-2324.patch, LUCENE-2324.patch, test.out, test.out,
> test.out
>
>
> See LUCENE-2293 for motivation and more details.
> I'm copying here Mike's summary he posted on 2293:
> Change the approach for how we buffer in RAM to a more isolated
> approach, whereby IW has N fully independent RAM segments
> in-process and when a doc needs to be indexed it's added to one of
> them. Each segment would also write its own doc stores and
> "normal" segment merging (not the inefficient merge we now do on
> flush) would merge them. This should be a good simplification in
> the chain (eg maybe we can remove the *PerThread classes). The
> segments can flush independently, letting us make much better
> concurrent use of IO & CPU.
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