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From Arvind Kalyan <>
Subject Lucene 4 single segment performance improvement tips?
Date Wed, 05 Mar 2014 09:18:07 GMT
Hi folks,

We are currently using Lucene 4.5 and we are hitting some bottlenecks and
appreciate some input from the community.

This particular index (the disk size for which is about 10GB) is guaranteed
to not have any updates, so we made it a single segment index by doing a
forceMerge(1). The index is guaranteed to be in-memory as well: we use the
MMapDirectory and the whole thing is mlocked after load. So there is no
disk I/O.

Our runtime/search use-case is very simple: run filters to select all docs
that match some conditions specified in a filter query (we do not use
Lucene scoring) and return the first 100 docs that match (this is an

On a machine with nothing else running, we are unable to move the needle on
CPU utilization to serve higher QPS. We see that most of the time is spent
in BlockTreeTermsReader.FieldReader.iterator() when we run profiling tools
to see where time is being spent. The CPU usage doesn't cross 30% (we have
multiple threads one per each client connected over a Jetty connection all
taken from a bounded thread-pool). We tried the usual suspects like
tweaking size of the threadpool, changing some jvm parameters like newsize,
heapsize, using cms for old gen, parnew for newgen, etc.

Does anyone here any pointers or general suggestions on how we can get good
performance out of Lucene 4.x? Specifically IndexSearcher performance
improvements for large, single-segment, atomicreaders.

I'll share more specifics if necessary but I'd like to hear from folks here
what your experience has been and what you did to speed up your
IndexSearchers to improve throughput *and/or* latency.


Arvind Kalyan

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