RFR: 8171855: Move package name transformations during module bootstrap into native code

[Lois Foltan]

On 1/5/2017 11:47 AM, Claes Redestad wrote:
> Hi,
>
> after a round of review comments I've now reworked this to do the
> transformations in the JNI layer rather than inside the VM, with
> similar - if not better - results.
>
> Webrevs:
> http://cr.openjdk.java.net/~redestad/8171855/hotspot.03/
> http://cr.openjdk.java.net/~redestad/8171855/jdk.03/
>
> Testing: RBT run in progress, all runtime/modules tests pass locally

Hi Claes,

Thank you for reworking this.  I think it looks good.  A couple of 
comments in hotspot/src/share/vm/classfile/modules.cpp

modules.cpp/Modules::define_module()
   line #278, I think it is important for the VM to validate the 
packages and num_packages parameters.
     An IllegalArgumentException should be thrown if:
     - num_packages is not >= 0
     - if packages == NULL, then num_packages should be equal to 0,
       this will protect against erroneously entering the for loop at 
line #292 based solely on num_packages
   line #291 - Ideally, if num_packages is 0, there is no sense in 
allocating pkg_list

Thanks,
Lois

>
> Thanks!
>
> /Claes
>
> On 01/02/2017 07:27 PM, Claes Redestad wrote:
>> Hi,
>>
>> during jigsaw bootstrap, package names - represented in external form,
>> "java.lang" - are transformed into VM internal form, "java/lang",
>> before calling into the VM.
>>
>> This, however, can effectively be moved into the VM, which removes the
>> need to generate a lot of short-lived strings during bootstrap and heat
>> up various String.replace-related methods.  This has a noticeable impact
>> on startup metrics.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8171855
>>
>