RFR(s): 8231630: Optimize boot loader with no bootclasspath append entry

[Jiangli Zhou]

Thanks, Claes!

Best regards,
Jiangli

On Sat, Oct 5, 2019 at 2:18 PM Claes Redestad <claes.redestad at oracle.com> wrote:
>
> Hi Jiangli,
>
> this looks good to me!
>
> Thanks!
>
> /Claes
>
> On 2019-10-05 22:28, Jiangli Zhou wrote:
> > Please review the following small optimization for boot loader.
> >
> > webrev: http://cr.openjdk.java.net/~jiangli/8231630/webrev.00/
> > RFE: https://bugs.openjdk.java.net/browse/JDK-8231630
> >
> > During classloading, the boot loader in the delegation path calls
> > SystemDictionary::load_instance_class to load a requested class. After
> > the module system is initialized, the VM checks if the requested
> > class' package is in a module defined to the boot loader. If the class
> > is either in the unnamed package or unnamed module, or in a module not
> > defined to the boot loader, the VM only searches the bootloader's
> > append entry (or entries). As a simple optimization, if there is no
> > boot append entry, we can immediately return NULL in that case without
> > any additional work. This particular call path is heavily exercised in
> > some microbenchmarks, such as Dacapo 'pmd'. The improvement is mostly
> > within noise level and may be un-noticeable for real world
> > applications, but does show a ~3% difference with 'pmd' in
> > Before/After comparison. As 'pmd' results can be noisy, the comparison
> > is done with a large number of benchmark runs.
> >
> > Testing with submit-repo tests.
> >
> > Best regards,
> > Jiangli
> >