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From "Aleksey Shipilev" <aleksey.shipi...@gmail.com>
Subject Re: [classlib][pack200] Decoupling I/O and processing for unpacking scenario
Date Fri, 18 Jul 2008 19:30:19 GMT
Andrew,

I forgot to discuss three things:

1. The order of segments is not preserved in MT (multithreaded)
version. Should we care about that?

2. MT version exposes GC problems since there are no more room for
separate GC thread like it was in ST (single-threaded). Can you print
-verbose:gc for your tests and see how much time spent in GC? Parallel
GC should help too. Larger heap should also help.

3. I had tested MT version on single 50 Mb .pack file, and I don't
know the performance profile for smaller files. What are the sizes for
your case?

Thanks,
Aleksey.

On Fri, Jul 18, 2008 at 9:20 PM, Andrew Cornwall
<andrew.pack200@gmail.com> wrote:
> I've been playing with HEAD + HARMONY-5916 + HARMONY-5918 on a dual-core
> machine (which is probably what the majority will have at least for now). On
> my 467-file test case, it takes 57 seconds (vs 38 for the nonthreaded
> version).
>
> It also looks as if it's doing something funny with resources (and possibly
> even some .class files). I see many more differences in output classes than
> I see with the nonthreaded version. (This may be a difference in output
> order of the JAR file: my diff tool is pretty limited).
>
> On Fri, Jul 18, 2008 at 8:46 AM, Sian January <sianjanuary@googlemail.com>
> wrote:
>
>> According to the spec, "The value #archive_size is either zero or declares
>> the number of bytes in the archive segment, starting immediately after
>> #archive_size_lo and before #archive_next_count and ending with the last
>> band, the *file_bits band. (That is, a non-zero size includes the size of
>> #archive_next_count, *file_bits, and everything in between.) "
>>
>> So you'll need to minus a few bytes for the values you've already read from
>> the second half of the header.
>>
>>
>> On 18/07/2008, Aleksey Shipilev <aleksey.shipilev@gmail.com> wrote:
>> >
>> > Sian,
>> >
>> > On Fri, Jul 18, 2008 at 5:29 PM, Sian January
>> > <sianjanuary@googlemail.com> wrote:
>> > >> Awesome! Am I understanding correctly: this value determines the size
>> > >> of segment? If yes, can you point me how to access this value? Is
>> > >> there API in current implementation?
>> > > Yes - use SegmentHeader.getArchiveSize()
>> >
>> > Does spec cover any alignment/padding constraints for segments?
>> > What exactly archive size specify?
>> >
>> > I'm doing this one [1]:
>> > 1. Reading the header of segment (moved from readSegment).
>> > 2. Check the field value, then either
>> > 3a. Read the segment into byte array and wrap it with BAIS, then
>> > read from BAIS
>> > 3b. Read the segment from global input stream
>> >
>> > I can only read first segment, second fails to read with the "bad
>> > header" exception.
>> >
>> > Thanks,
>> > Aleksey.
>> >
>> > [1]
>> >    void unpackRead(InputStream in) throws IOException, Pack200Exception {
>> >        if (!in.markSupported())
>> >            in = new BufferedInputStream(in);
>> >
>> >        header = new SegmentHeader(this);
>> >        header.read(in);
>> >
>> >        int size = (int)header.getArchiveSize();
>> >
>> >        if (size != 0) {
>> >            byte[] data = new byte[size];
>> >            in.read(data);
>> >            bin = new ByteArrayInputStream(data);
>> >
>> >            readSegment(bin);
>> >        } else {
>> >            readSegment(in);
>> >        }
>> >    }
>> >
>>
>>
>>
>> --
>> Unless stated otherwise above:
>> IBM United Kingdom Limited - Registered in England and Wales with number
>> 741598.
>> Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
>>
>

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