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From "Michael McCandless (JIRA)" <>
Subject [jira] Commented: (LUCENE-888) Improve indexing performance by increasing internal buffer sizes
Date Thu, 24 May 2007 17:55:17 GMT


Michael McCandless commented on LUCENE-888:

> > I wonder if we should just add a ctor to BufferedIndexInput that takes
> > the bufferSize? This would avoid the surprising API caveat you
> > describe above. The problem is, then all classes (SegmentTermDocs,
> > SegmentTermPositions, FieldsReader, etc.) that open an IndexInput
> > would also have to have ctors to change buffer sizes. Even if we do
> > setBufferSize instead of new ctor we have some cases (eg at least
> > SegmentTermEnum) where bytes are read during construction so it's too
> > late for caller to then change buffer size. Hmmm. Not clear how to
> > do this cleanly...
> Yeah I was thinking about the ctor approach as well. Actually 
> BufferedIndexInput does not have a public ctor so far, it's created by 
> using Directory.openInput(String fileName). And to add a new ctor would 
> mean an API change, so subclasses wouldn't compile anymore without 
> changes. 

Actually, it does have a default public constructor right?  Ie if we add

  public BufferedIndexInput()
  public BufferedIndexInput(int bufferSize)

then I think we don't break API backwards compatibility?

> After a clone however, we would still have to cast to
> BufferedIndexInput before setBufferSize() can be called.

I plan to add "private int bufferSize" to BufferedIndexInput,
defaulting to BUFFER_SIZE.  I think then it would just work w/ your
LUCENE-430 patch because your patch sets the clone's buffer to null
and then when the clone allocates its buffer it will be length
bufferSize.  I think?

> Improve indexing performance by increasing internal buffer sizes
> ----------------------------------------------------------------
>                 Key: LUCENE-888
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>    Affects Versions: 2.1
>            Reporter: Michael McCandless
>         Assigned To: Michael McCandless
>            Priority: Minor
> In working on LUCENE-843, I noticed that two buffer sizes have a
> substantial impact on overall indexing performance.
> First is BufferedIndexOutput.BUFFER_SIZE (also used by
> BufferedIndexInput).  Second is CompoundFileWriter's buffer used to
> actually build the compound file.  Both are now 1 KB (1024 bytes).
> I ran the same indexing test I'm using for LUCENE-843.  I'm indexing
> ~5,500 byte plain text docs derived from the Europarl corpus
> (English).  I index 200,000 docs with compound file enabled and term
> vector positions & offsets stored plus stored fields.  I flush
> documents at 16 MB RAM usage, and I set maxBufferedDocs carefully to
> not hit LUCENE-845.  The resulting index is 1.7 GB.  The index is not
> optimized in the end and I left mergeFactor @ 10.
> I ran the tests on a quad-core OS X 10 machine with 4-drive RAID 0 IO
> system.
> At 1 KB (current Lucene trunk) it takes 622 sec to build the index; if
> I increase both buffers to 8 KB it takes 554 sec to build the index,
> which is an 11% overall gain!
> I will run more tests to see if there is a natural knee in the curve
> (buffer size above which we don't really gain much more performance).
> I'm guessing we should leave BufferedIndexInput's default BUFFER_SIZE
> at 1024, at least for now.  During searching there can be quite a few
> of this class instantiated, and likely a larger buffer size for the
> freq/prox streams could actually hurt search performance for those
> searches that use skipping.
> The CompoundFileWriter buffer is created only briefly, so I think we
> can use a fairly large (32 KB?) buffer there.  And there should not be
> too many BufferedIndexOutputs alive at once so I think a large-ish
> buffer (16 KB?) should be OK.

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