RFR(S) 8240205: Avoid PackageEntry lookup when loading shared classes

Calvin Cheung calvin.cheung at oracle.com
Fri Apr 3 17:23:27 UTC 2020

Hi Lois,

Thanks for your review!

On 4/3/20 9:46 AM, Lois Foltan wrote:
> On 4/2/2020 8:58 PM, Calvin Cheung wrote:
>> RFE: https://bugs.openjdk.java.net/browse/JDK-8240205
>> webrev: http://cr.openjdk.java.net/~ccheung/jdk15/8240205/webrev.00/
>> During loading of a shared class from a CDS archive, the PackageEntry 
>> is being looked up in several places within the same call stack. This 
>> RFE is to do the PackageEntry lookup at one place and then pass it 
>> along to the subsequently called functions which need it.
>> Perf improvement on loading approx. 2000 classes on linux:
>> instr delta = -17930620 -0.6155%
>> time delta = -6.311 ms -0.7516%
>> Passed tiers1 - 4 testing.
>> thanks,
>> Calvin
> Hi Calvin,
> This looks good & promising on the numbers!  I have a slight concern 
> that you've introduced yet another "get package entry from name" sort 
> of function in SystemDictionaryShared. classfile/modules.cpp already 
> contains a static method get_package_entry_by_name() but it operates 
> on a package name not a class name.  Please consider moving 
> SystemDictionaryShared::get_package_entry_from_class_name into 
> ClassLoader near ClassLoader::get_package_from_class_name().  That 
> seems like a more consistent place to add it that various areas of the 
> JVM can take advantage of.

The SystemDictionaryShared::get_package_entry_from_class_name function 
is currently being used only within the SharedDictionaryShared class. 
That's why it was declared private and I think that's the right place 
for it.

There also another SystemDictionaryShared::get_package_entry() which 
operates on a package name and is very similar to the one in 
ClassLoader. I can file another RFE to consolidate those 2 functions.



> Thanks,
> Lois

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