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https://issues.apache.org/jira/browse/LUCENE-4864?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13611309#comment-13611309
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Michael McCandless commented on LUCENE-4864:
--------------------------------------------
Linux, all wikipedia docs (wikimediumall), SimpleFSDir vs AsyncFSDir,
using 3 search threads:
{noformat}
Task QPS base StdDev QPS comp StdDev
Pct diff
Respell 29.43 (0.0%) 5.60 (0.0%)
-81.0% ( -80% - -80%)
AndHighLow 352.00 (0.0%) 68.00 (0.0%)
-80.7% ( -80% - -80%)
LowPhrase 15.94 (0.0%) 3.28 (0.0%)
-79.4% ( -79% - -79%)
Fuzzy2 40.14 (0.0%) 8.79 (0.0%)
-78.1% ( -78% - -78%)
Fuzzy1 39.92 (0.0%) 9.65 (0.0%)
-75.8% ( -75% - -75%)
LowSloppyPhrase 19.18 (0.0%) 5.17 (0.0%)
-73.0% ( -73% - -73%)
AndHighMed 62.82 (0.0%) 19.42 (0.0%)
-69.1% ( -69% - -69%)
Wildcard 22.52 (0.0%) 8.09 (0.0%)
-64.1% ( -64% - -64%)
HighPhrase 10.12 (0.0%) 3.72 (0.0%)
-63.2% ( -63% - -63%)
LowSpanNear 8.25 (0.0%) 3.29 (0.0%)
-60.1% ( -60% - -60%)
MedPhrase 115.26 (0.0%) 48.02 (0.0%)
-58.3% ( -58% - -58%)
MedTerm 74.15 (0.0%) 31.30 (0.0%)
-57.8% ( -57% - -57%)
MedSloppyPhrase 25.16 (0.0%) 11.35 (0.0%)
-54.9% ( -54% - -54%)
HighTerm 60.19 (0.0%) 27.50 (0.0%)
-54.3% ( -54% - -54%)
AndHighHigh 17.72 (0.0%) 8.75 (0.0%)
-50.6% ( -50% - -50%)
HighSpanNear 3.28 (0.0%) 1.69 (0.0%)
-48.3% ( -48% - -48%)
HighSloppyPhrase 0.76 (0.0%) 0.40 (0.0%)
-48.0% ( -48% - -48%)
MedSpanNear 29.04 (0.0%) 15.41 (0.0%)
-46.9% ( -46% - -46%)
OrHighLow 25.70 (0.0%) 13.96 (0.0%)
-45.7% ( -45% - -45%)
OrHighMed 27.11 (0.0%) 14.76 (0.0%)
-45.5% ( -45% - -45%)
OrHighHigh 15.32 (0.0%) 8.37 (0.0%)
-45.4% ( -45% - -45%)
IntNRQ 3.10 (0.0%) 1.78 (0.0%)
-42.5% ( -42% - -42%)
Prefix3 17.69 (0.0%) 10.26 (0.0%)
-42.0% ( -42% - -42%)
LowTerm 334.97 (0.0%) 211.06 (0.0%)
-37.0% ( -36% - -36%)
{noformat}
> Add AsyncFSDirectory to work around Windows issues with NIOFS (Lucene 5.0
> only)
> -------------------------------------------------------------------------------
>
> Key: LUCENE-4864
> URL: https://issues.apache.org/jira/browse/LUCENE-4864
> Project: Lucene - Core
> Issue Type: Improvement
> Components: core/store
> Affects Versions: 5.0
> Reporter: Michael Poindexter
> Attachments: LUCENE-4864.patch, LUCENE-4864.patch
>
>
> On LUCENE-4848 a new directory implementation was proposed that uses
> AsyncFileChannel to make a sync-less directory implementation (only needed
> for IndexInput). The problem on Windows is that positional reads are
> impossible without overlapping (async) I/O, so FileChannel in the JDK has to
> syncronize all reads, because they consist of an atomic seek and atomic read.
> AsyncFSDirectoty would not have this issue, but has to take care of thread
> management, because you need a separate thread to get notified when the read
> is done. This involves overhead, but might still be better than the
> synchronization.
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