Thanks for running more tests, Michael.
It is encouraging that you saw a similar performance between 9.3 and 9.4. I
will also run more tests with different parameters.
On Tue, Sep 13, 2022 at 9:30 AM Michael Sokolov <msoko...@gmail.com> wrote:
> As a follow-up, I ran a test using the same parameters as above, only
> changing M=200 to M=16. This did result in a single segment in both
> cases (9.3, 9.4) and the performance was pretty similar; within noise
> I think. The main difference I saw was that the 9.3 index was written
> using CFS:
>
> 9.4:
> recall latency nDoc fanout maxConn beamWidth visited index ms
> 0.755 1.36 1000000 100 16 100 200 891402 1.00
> post-filter
> -rw-r--r-- 1 sokolovm amazon 382M Sep 13 13:06
> _0_Lucene94HnswVectorsFormat_0.vec
> -rw-r--r-- 1 sokolovm amazon 262K Sep 13 13:06
> _0_Lucene94HnswVectorsFormat_0.vem
> -rw-r--r-- 1 sokolovm amazon 131M Sep 13 13:06
> _0_Lucene94HnswVectorsFormat_0.vex
>
> 9.3:
> recall latency nDoc fanout maxConn beamWidth visited index ms
> 0.775 1.34 1000000 100 16 100 4033 977043
> rw-r--r-- 1 sokolovm amazon 297 Sep 13 13:26 _0.cfe
> -rw-r--r-- 1 sokolovm amazon 516M Sep 13 13:26 _0.cfs
> -rw-r--r-- 1 sokolovm amazon 340 Sep 13 13:26 _0.si
>
> On Tue, Sep 13, 2022 at 8:50 AM Michael Sokolov <msoko...@gmail.com>
> wrote:
> >
> > I ran another test. I thought I had increased the RAM buffer size to
> > 8G and heap to 16G. However I still see two segments in the index that
> > was created. And looking at the infostream I see:
> >
> > dir=MMapDirectory@
> /local/home/sokolovm/workspace/knn-perf/glove-100-angular.hdf5-train-200-200.index
> > lockFactory=org\
> > .apache.lucene.store.NativeFSLockFactory@4466af20
> > index=
> > version=9.4.0
> > analyzer=org.apache.lucene.analysis.standard.StandardAnalyzer
> > ramBufferSizeMB=8000.0
> > maxBufferedDocs=-1
> > ...
> > perThreadHardLimitMB=1945
> > ...
> > DWPT 0 [2022-09-13T02:42:53.329404950Z; main]: flush postings as
> > segment _6 numDocs=555373
> > IW 0 [2022-09-13T02:42:53.330671171Z; main]: 0 msec to write norms
> > IW 0 [2022-09-13T02:42:53.331113184Z; main]: 0 msec to write docValues
> > IW 0 [2022-09-13T02:42:53.331320146Z; main]: 0 msec to write points
> > IW 0 [2022-09-13T02:42:56.424195657Z; main]: 3092 msec to write vectors
> > IW 0 [2022-09-13T02:42:56.429239944Z; main]: 4 msec to finish stored
> fields
> > IW 0 [2022-09-13T02:42:56.429593512Z; main]: 0 msec to write postings
> > and finish vectors
> > IW 0 [2022-09-13T02:42:56.430309031Z; main]: 0 msec to write fieldInfos
> > DWPT 0 [2022-09-13T02:42:56.431721622Z; main]: new segment has 0 deleted
> docs
> > DWPT 0 [2022-09-13T02:42:56.431921144Z; main]: new segment has 0
> > soft-deleted docs
> > DWPT 0 [2022-09-13T02:42:56.435738086Z; main]: new segment has no
> > vectors; no norms; no docValues; no prox; freqs
> > DWPT 0 [2022-09-13T02:42:56.435952356Z; main]:
> > flushedFiles=[_6_Lucene94HnswVectorsFormat_0.vec, _6.fdm, _6.fdt, _6_\
> > Lucene94HnswVectorsFormat_0.vem, _6.fnm, _6.fdx,
> > _6_Lucene94HnswVectorsFormat_0.vex]
> > DWPT 0 [2022-09-13T02:42:56.436121861Z; main]: flushed codec=Lucene94
> > DWPT 0 [2022-09-13T02:42:56.437691468Z; main]: flushed: segment=_6
> > ramUsed=1,945.002 MB newFlushedSize=1,065.701 MB \
> > docs/MB=521.134
> >
> > so I think it's this perThreadHardLimit that is triggering the
> > flushes? TBH this isn't something I had seen before; but the docs say:
> >
> > /**
> > * Expert: Sets the maximum memory consumption per thread triggering
> > a forced flush if exceeded. A
> > * {@link DocumentsWriterPerThread} is forcefully flushed once it
> > exceeds this limit even if the
> > * {@link #getRAMBufferSizeMB()} has not been exceeded. This is a
> > safety limit to prevent a {@link
> > * DocumentsWriterPerThread} from address space exhaustion due to
> > its internal 32 bit signed
> > * integer based memory addressing. The given value must be less
> > that 2GB (2048MB)
> > *
> > * @see #DEFAULT_RAM_PER_THREAD_HARD_LIMIT_MB
> > */
> >
> > On Mon, Sep 12, 2022 at 6:28 PM Michael Sokolov <msoko...@gmail.com>
> wrote:
> > >
> > > Hi Mayya, thanks for persisting - I think we need to wrestle this to
> > > the ground for sure. In the test I ran, RAM buffer was the default
> > > checked in, which is weirdly: 1994MB. I did not specifically set heap
> > > size. I used maxConn/M=200. I'll try with larger buffer to see if I
> > > can get 9.4 to produce a single segment for the same test settings. I
> > > see you used a much smaller M (16), which should have produced quite
> > > small graphs, and I agree, should have been a single segment. Were you
> > > able to verify the number of segments?
> > >
> > > Agree that decrease in recall is not expected when more segments are
> produced.
> > >
> > > On Mon, Sep 12, 2022 at 1:51 PM Mayya Sharipova
> > > <mayya.sharip...@elastic.co.invalid> wrote:
> > > >
> > > > Hello Michael,
> > > > Thanks for checking.
> > > > Sorry for bringing this up again.
> > > > First of all, I am ok with proceeding with the Lucene 9.4 release
> and leaving the performance investigations for later.
> > > >
> > > > I am interested in what's the maxConn/M value you used for your
> tests? What was the heap memory and the size of the RAM buffer for indexing?
> > > > Usually, when we have multiple segments, recall should increase, not
> decrease. But I agree that with multiple segments we can see a big drop in
> QPS.
> > > >
> > > > Here is my investigation with detailed output of the performance
> difference between 9.3 and 9.4 releases. In my tests I used a large
> indexing buffer (2Gb) and large heap (5Gb) to end up with a single segment
> for both 9.3 and 9.4 tests, but still see a big drop in QPS in 9.4.
> > > >
> > > > Thank you.
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > On Fri, Sep 9, 2022 at 12:21 PM Alan Woodward <romseyg...@gmail.com>
> wrote:
> > > >>
> > > >> Done. Thanks!
> > > >>
> > > >> > On 9 Sep 2022, at 16:32, Michael Sokolov <msoko...@gmail.com>
> wrote:
> > > >> >
> > > >> > Hi Alan - I checked out the interval queries patch; seems pretty
> safe,
> > > >> > please go ahead and port to 9.4. Thanks!
> > > >> >
> > > >> > Mike
> > > >> >
> > > >> > On Fri, Sep 9, 2022 at 10:41 AM Alan Woodward <
> romseyg...@gmail.com> wrote:
> > > >> >>
> > > >> >> Hi Mike,
> > > >> >>
> > > >> >> I’ve opened https://github.com/apache/lucene/pull/11760 as a
> small bug fix PR for a problem with interval queries. Am I OK to port this
> to the 9.4 branch?
> > > >> >>
> > > >> >> Thanks, Alan
> > > >> >>
> > > >> >> On 2 Sep 2022, at 20:42, Michael Sokolov <msoko...@gmail.com>
> wrote:
> > > >> >>
> > > >> >> NOTICE:
> > > >> >>
> > > >> >> Branch branch_9_4 has been cut and versions updated to 9.5 on
> stable branch.
> > > >> >>
> > > >> >> Please observe the normal rules:
> > > >> >>
> > > >> >> * No new features may be committed to the branch.
> > > >> >> * Documentation patches, build patches and serious bug fixes may
> be
> > > >> >> committed to the branch. However, you should submit all patches
> you
> > > >> >> want to commit to Jira first to give others the chance to review
> > > >> >> and possibly vote against the patch. Keep in mind that it is our
> > > >> >> main intention to keep the branch as stable as possible.
> > > >> >> * All patches that are intended for the branch should first be
> committed
> > > >> >> to the unstable branch, merged into the stable branch, and then
> into
> > > >> >> the current release branch.
> > > >> >> * Normal unstable and stable branch development may continue as
> usual.
> > > >> >> However, if you plan to commit a big change to the unstable
> branch
> > > >> >> while the branch feature freeze is in effect, think twice: can't
> the
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> > > >> >> may become more difficult.
> > > >> >> * Only Jira issues with Fix version 9.4 and priority "Blocker"
> will delay
> > > >> >> a release candidate build.
> > > >> >>
> > > >> >>
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