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From "Earwin Burrfoot (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-2324) Per thread DocumentsWriters that write their own private segments
Date Mon, 15 Mar 2010 17:05:27 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-2324?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12845408#action_12845408
] 

Earwin Burrfoot commented on LUCENE-2324:
-----------------------------------------

> Seems ilke it's 8 bytes
Object header is two words, so that's 16bytes for 64bit arch. (probably 12 for 64bit+CompressedOops?)

Also, GC time is (roughly) linear in number of objects on heap, so replacing single huge array
of objects with few huge primitive arrays for their fields does miracles to your GC delays.

> 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: 3.1
>
>
> 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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