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Type:
Improvement
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Status: Resolved
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Priority:
Major
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Resolution: Fixed
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Affects Version/s: 3.1, 4.0-ALPHA
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Fix Version/s: None
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Component/s: core/store
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Labels:None
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Lucene Fields:New, Patch Available
MMapDirectory has some performance problems:
- When the file is larger than Integer.MAX_VALUE, we use MultiMMapIndexInput,
which does a lot of unnecessary bounds-checks for its buffer-switching etc.
Instead, like MMapIndexInput, it should rely upon the contract of these operations
in ByteBuffer (which will do a bounds check always and throw BufferUnderflowException).
Our 'buffer' is so large (Integer.MAX_VALUE) that its rare this happens and doing
our own bounds checks just slows things down. - the readInt()/readLong()/readShort() are slow and should just defer to ByteBuffer.readInt(), etc
This isn't very important since we don't much use these, but I think there's no reason
users (e.g. codec writers) should have to readBytes() + wrap as bytebuffer + get an
IntBuffer view when readInt() can be almost as fast...