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From "Robert Muir (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-3178) Native MMapDir
Date Wed, 31 Aug 2011 18:28:10 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-3178?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13094754#comment-13094754
] 

Robert Muir commented on LUCENE-3178:
-------------------------------------

Here are the old benchmarks from such a technique, with no bounds checks (only asserts) and
unsafe, versus using a mappedbytebuffer
||Task||QPS base||StdDev base||QPS unsafemmap||StdDev unsafemmap||Pct diff||
|Fuzzy2|21.83|0.58|21.94|1.32|-7% - 9%|
|Respell|25.68|0.13|26.01|0.91|-2% - 5%|
|Fuzzy1|27.70|0.78|28.39|1.48|-5% - 10%|
|TermGroup1M|35.96|1.38|38.92|0.53|2% - 14%|
|PKLookup|41.56|1.05|46.04|1.82|3% - 18%|
|SloppyPhrase|7.06|0.26|7.93|0.43|2% - 22%|
|TermBGroup1M|29.09|1.57|32.70|0.70|4% - 21%|
|TermBGroup1M1P|32.13|1.94|36.86|0.44|6% - 23%|
|SpanNear|6.71|0.12|7.89|0.13|13% - 21%|
|Wildcard|37.62|3.83|44.39|1.41|3% - 35%|
|AndHighHigh|14.53|0.50|17.56|1.12|9% - 33%|
|Phrase|12.20|0.63|14.82|0.35|12% - 31%|
|OrHighHigh|11.77|0.79|14.31|0.26|11% - 32%|
|OrHighMed|11.49|0.75|14.02|0.26|12% - 32%|
|Prefix3|32.70|4.10|40.06|1.77|4% - 46%|
|Term|92.02|6.37|114.13|1.68|14% - 35%|
|AndHighMed|55.38|1.60|69.02|5.48|11% - 38%|
|IntNRQ|7.17|1.19|8.96|0.63|0% - 60%|


> Native MMapDir
> --------------
>
>                 Key: LUCENE-3178
>                 URL: https://issues.apache.org/jira/browse/LUCENE-3178
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: core/store
>            Reporter: Michael McCandless
>
> Spinoff from LUCENE-2793.
> Just like we will create native Dir impl (UnixDirectory) to pass the right OS level IO
flags depending on the IOContext, we could in theory do something similar with MMapDir.
> The problem is MMap is apparently quite hairy... and to pass the flags the native code
would need to invoke mmap (I think?), unlike UnixDir where the code "only" has to open the
file handle.

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