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https://issues.apache.org/jira/browse/LUCENE-888?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12499018
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Michael McCandless commented on LUCENE-888:
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OK I ran two sets of tests. First is only on Mac OS X to see how
performance changes with buffer sizes. Second was also on Debian
Linux & Windows XP Pro.
The performance gains are 10-18% faster overall.
FIRST TEST
I increased buffer sizes, separately, for each of BufferedIndexInput,
BufferedIndexOutput and CompoundFileWriter. Each test is run once on
Mac OS X:
BufferedIndexInput
1 K 622 sec (current trunk)
4 K 607 sec
8 K 606 sec
16 K 598 sec
32 K 606 sec
64 K 589 sec
128 K 601 sec
CompoundFileWriter
1 K 622 sec (current trunk)
4 K 599 sec
8 K 591 sec
16 K 578 sec
32 K 583 sec
64 K 580 sec
BufferedIndexOutput
1 K 622 sec (current trunk)
4 K 588 sec
8 K 576 sec
16 K 551 sec
32 K 566 sec
64 K 555 sec
128 K 543 sec
256 K 534 sec
512 K 564 sec
Comments:
* The results are fairly noisy, but, performance does generally get
better w/ larger buffers.
* BufferedIndexOutput seems specifically to like very large output
buffers; the other two seem to have less but still significant
effect.
Given this I picked 16 K buffer for BufferedIndexOutput, 16 K buffer
for CompoundFileWriter and 4 K buffer for BufferedIndexInput. I think
we would get faster performance for a larger buffer for
BufferedIndexInput, but, even when merging there are quite a few of
these created (mergeFactor * N where N = number of separate index
files).
Then, I re-tested the baseline (trunk) & these buffer sizes across
platforms (below):
SECOND TEST
Baseline (trunk) = 1 K buffers for all 3. New = 16 K for
BufferedIndexOutput, 16 K for CompoundFileWriter and 4 K for
BufferedIndexInput.
I ran each test 4 times & took the best time:
Quad core Mac OS X on 4-drive RAID 0
baseline 622 sec
new 527 sec
-> 15% faster
Dual core Debian Linux (2.6.18 kernel) on 6 drive RAID 5
baseline 708 sec
new 635 sec
-> 10% faster
Windows XP Pro laptop, single drive
baseline 1604 sec
new 1308 sec
-> 18% faster
Net/net it's between 10-18% performance gain overall. It is
interesting that the system with the "weakest" IO system (one drive on
Windows XP vs RAID 0/5 on the others) has the best gains.
> Improve indexing performance by increasing internal buffer sizes
> ----------------------------------------------------------------
>
> Key: LUCENE-888
> URL: https://issues.apache.org/jira/browse/LUCENE-888
> 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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