RFR(S): 8242848: Improve performance of InflaterOutputStream.write()

[Thomas Stüfe]

Hi Volker,

looks good now. Only a nit, really, but since this is pretty much binary
now (we either have the whole input or have it given to the inflater),
setting len=0 seems weird, maybe add a boolean like "inputFedToInflater"?
But I leave it up to you, this is just idle nitpicking. I am fine with the
current version.

Nice test :)

Thomas


On Fri, Apr 17, 2020 at 12:50 PM Volker Simonis <volker.simonis at gmail.com>
wrote:

> Thanks everybody for looking at this change!
>
> Please find an updated webrev (with a new test and micro-benchmark)
> and my answers to your comments below:
>
> http://cr.openjdk.java.net/~simonis/webrevs/2020/8242848.01/
>
> On Thu, Apr 16, 2020 at 6:40 AM Vyom Tiwari <vyommani at gmail.com> wrote:
> > Thanks for doing this, i think the below code change is not required .
> >
> > Please do let me know if i am not reading it correctly.
> >
> > if (inf.finished() || (len == 0)/* no more input */) {
> >
> > If you check the native code "inf.finished() will be true only of the
> corresponding native call inflate(strm, Z_PARTIAL_FLUSH) returns
> "Z_STREAM_END".
> >
> > After your code change  write may return even if finished() is not true.
>
> Yes, that's true, but that's what we must do if there's no more input
> available. Before my change this break on "len < 1" was in the "if
> (inf.needsInput())" branch.
>
> On Thu, Apr 16, 2020 at 8:22 AM Thomas Stüfe <thomas.stuefe at gmail.com>
> wrote:
> >  252                 // Check the decompressor
> >  253                 if (inf.finished() || (len == 0)/* no more input
> */) {
> >  254                     break;
> >  255                 }
> >
> > Not sure but I think this is wrong because now you bypass the followup
> handling of inf.needsDirectory.
> >
> > Inflater.inflate() returns 0 if either needsInput or needsDirectory. We
> have to ignore needsInput since we have no input anymore, but
> needsDirectory has to be handled, no?
>
> You're absolutely right Thomas. Thanks for catching this! I've moved
> the check for "needsDictionary" in front of the "finished() || len ==
> 0" check.
>
> Unfortunately there is not very good test coverage for zip with preset
> dictionaries (jtreg and submit repo passed without problems). So I
> added a new test for this use case to "
> test/jdk/java/util/zip/DeflateIn_InflateOut.java".
>
> On Thu, Apr 16, 2020 at 8:48 AM Thomas Stüfe <thomas.stuefe at gmail.com>
> wrote:
> >
> > As for increasing the buffer size, it makes sense but IMHO needs a CSR
> and a release note.
>
> I don't think so. This is an internal, implementation specific setting
> which has never been exposed or documented before so I don't see why
> we should document it now. But let's discuss this separately in the
> corresponding JBS issue (see below).
>
> On Thu, Apr 16, 2020 at 1:18 PM Claes Redestad
> <claes.redestad at oracle.com> wrote:
> >
> > Hi Volker,
> >
> > On 2020-04-15 19:48, Volker Simonis wrote:
> > > While doing this change, I've also realized that all the streams in
> > > java.util.zip (i.e. DeflaterInputStream, GZIPInputStream,
> > > GZIPOutputStream, InflaterInputStream, DeflaterOutputStream) use an
> > > internal byte buffer of 512 bytes by default. Looking at the benchmark
> > > attached to JDK-8242864, I think that increasing this default to a
> > > bigger size (e.g. 4096 bytes) will considerably speed up (up to 50%)
> > > read and write operations on these streams when they are created with
> > > the default buffer size. I think the value "512" is a legacy of old
> > > times when memory was more precious:)  so  I've opened "JDK-8242864:
> > > Increase the default, internal buffer size of the Streams in
> > > java.util.zip" to track that as as separate issue. Do you think it
> > > makes sense to increase that default value?
> >
> > Seems reasonable. 8192 seems to be the buffer size we've been converging
> > on elsewhere (see InputStream, BufferedInputStream, Files, ..). I also
>
> That seems reasonable. Alan commented on the JBS issue so we can
> continue the discussion there.
>
> > found an instance of 8096, which is either a typo or a clever
> > optimization to keep the array + array object header fit snugly within
> > 8Kb. You chose. :-)
> >
>
> I like how you try to be positive :)
>
> > >
> > > Thank you and best regards,
> > > Volker
> > >
> > > PS: do you think it makes sense to contribute the benchmark attached
> > > to JDK-8242864 to the code-tools/mh-jdk-microbenchmarks [1] project?
> > >
> > > [1]
> http://openjdk.java.net/projects/code-tools/jmh-jdk-microbenchmarks/
> >
> > I'd definitely welcome the micro as part of the patch under
> > test/micro/org/openjdk/bench/java/util/zip - additionally contributing
>
> I knew that "jmh-jdk-microbenchmarks" has been copied to the jdk repo
> but somehow I did found "jmh-jdk-microbenchmarks" before looking in
> the obvious place :)
>
> So I've added the benchmark to the patch now. There's one thing I'm
> not sure however. The benchmark requires a "big" (several 100k) with
> good compression ratio (e.g. a large text file). I've decided to use a
> big Java source file from "src.zip" but I'm not sure if "src.zip" is
> always available in the jdk images which are used to run the
> microbenchmarks. Do you think the test it is fine this way or do you
> have a better idea? I saw that "ZipFind" uses "microbenchmarks.jar"
> (i.e. the container of the test itself) but that file is already
> compressed so the compression rate won't be that good.
>
> Another thing I couldn't figure out is a good way to skip the
> benchmark when I realize that I can't load the expected file in the
> "@Setup" method. Do you now anything better than just throwing an
> exception?
>
> Thank you and best regards,
> Volker
>
> > to jmh-jdk-microbenchmarks could enable you to test the micro on 8 or
> > 11.
> >
> > /Claes
> >
>