RFR: 8241371: Refactor and consolidate package_from_name

[Ioi Lam]

Hi Claes,

This is a good optimization. Looks good to me. Here are some minor nits:

[1] ClassLoader::search_module_entries may be called twice by the same 
caller,
     I think it's better to compute the mod_entry in the caller, so you 
can avoid
     the pkg_entry lookup twice.

[2] For tracking the code changes, I think it's better to move your new 
version
     of InstanceKlass::package_from_name() to 
ClassLoader::package_from_name().

     I did a diff of the new version of 
InstanceKlass::package_from_name() and
     the old version of ClassLoader::package_from_name(), and I can see 
that the
     logic has not changed (the only changes are how we allocate the 
buffers).

     With the current patch, it's hard to see what has changed and 
difficult to
     validate its correctness.

     Also, it's better to rename the function to
     ClassLoader::package_from_class_name()

Thanks
- Ioi



On 3/22/20 2:22 PM, Claes Redestad wrote:
> Correct webrev: http://cr.openjdk.java.net/~redestad/8241371/open.00/
> Bug:            https://bugs.openjdk.java.net/browse/JDK-8241371
>
> On 2020-03-22 17:15, Claes Redestad wrote:
>> Hi,
>>
>> JDK-8153858 partially consolidated the logic shared between
>> InstanceKlass::package_from_name and ClassLoader::package_from_name.
>> Unfortunately it also caused an undetected regression in some paths due
>> need to copy from Symbol -> resource arrays and back again.
>>
>> By refactoring package_from_name into a single implementation which
>> operates on a Symbol* rather than a char* we can both simplify a bit
>> and regain some lost performance:
>>
>> Testing: tier1-5, verified a ~0.5% improvement on startup
>>
>> Thanks!
>>
>> /Claes