Loading classes with many methods is very expensive

[Jeremy Manson]

Just want to reiterate: that patch has a few bugs in it.  Don't review it
yet.  I'll probably follow up tomorrow.

Jeremy

On Mon, Oct 27, 2014 at 4:37 PM, Jeremy Manson <jeremymanson at google.com>
wrote:

> Jeremy has already filed a bug (8062116), and is just finishing up the
> patch (I jumped the gun a bit by attaching it to the bug - it has a few
> bugs in it).  I'll probably have something in reasonable shape to review
> tomorrow (I've submitted it internally, and I want to let it spend a day or
> so having our test infrastructure throw things at it).
>
> It's actually a JVMTI performance regression.  The data structure that is
> being used to store jmethodids isn't great.  I've refactored it a bit to
> improve its performance, but it should really be a closed hash table.
> There isn't a handy one in HS, so I just made it O(1) for writes.  It's
> still O(n) for reads, though, which is nasty.
>
> We can have the real conversation when I post the RFR, though.
>
> Jeremy
>
> On Mon, Oct 27, 2014 at 12:45 PM, Aleksey Shipilev <
> aleksey.shipilev at oracle.com> wrote:
>
>> On 27.10.2014 22:01, Martin Buchholz wrote:
>> > I'm having trouble keeping up with this thread I started, but I did
>> > update the test/benchmark
>> >
>> http://cr.openjdk.java.net/~martin/webrevs/openjdk9/Class.getMethods-benchmark/
>> > <
>> http://cr.openjdk.java.net/%7Emartin/webrevs/openjdk9/Class.getMethods-benchmark/
>> >
>> >
>> > I added a test *LoadAllClassesAndMethods *that does what its name says.
>> > Although originally written as just a benchmark,
>>
>> In our recent Nashorn classloading work, we did this benchmark:
>>  http://cr.openjdk.java.net/~shade/8053904/ClassLoaderBenchmark.java
>>
>> ...which, I think can be easily exploded to call getMethods() as well.
>>
>>
>> > Jeremy is independently working on yet another performance problem
>> > exposed by *LoadAllClassesAndMethods*
>>
>> Does Jeremy have a reportable outline? Submit the bug to make this
>> thread short :)
>>
>>
>> Thanks,
>> -Aleksey.
>>
>>
>>
>