RFR: 8245024: Simplify and eagerly initialize StringConcatFactory

[Claes Redestad]

On 2020-05-14 17:05, Jim Laskey wrote:
> Will this have an effect on JDK-8218173 
> <https://bugs.openjdk.java.net/browse/JDK-8218173> ?

Interesting that you ask, since this cleanup was extracted from an
attempted fix for 8218173.

_Potentially_ this helps. But it won't fix it.

Ensuring SCF.class is initialized reduces risk that we'll hit certain
OOMEs when going into the BSM in a constrained environment, but doesn't
eliminate the corner case in 8218173 entirely.

Initializing the strategy up front might solve more of the issues
in 8218173, but it's a slippery slope and it'd regress startup (likely
adds ~5ms to startup due the MH lookups). As I was looking at an eager
initialization I ran into weird bootstrapping issues, too, so I've
backed away from trying to solve 8218173.

/Claes

> 
>> On May 14, 2020, at 11:39 AM, Claes Redestad 
>> <claes.redestad at oracle.com <mailto:claes.redestad at oracle.com>> wrote:
>>
>> Hi,
>>
>> JDK-8155090 added some measures to StringConcatFactory to prevent
>> certain bootstrapping issues. I think we should consider eagerly
>> initializing the StringConcatFactory base class during bootstrap
>> instead.
>>
>> Doing so will add a tiny bit of class loading overhead to bootstrap
>> (which of course will be amortized on first use of SCF) but still this
>> would also be a good opportunity to clean up a little.
>>
>> One straightforward means to do so is to move the CACHE, DUMPER and
>> CACHE_ENABLE fields to BytecodeStringBuilderStrategy, since it's the
>> only place where they are used (the MethodHandle based strategies don't
>> manually spin classes and rely on LF sharing to de-duplicate shared
>> components).
>>
>> Webrev: http://cr.openjdk.java.net/~redestad/8245024/open.00/
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8245024
>>
>> This reduces initialization overhead and simplifices bootstraps for the
>> default case, while still passing relevant test cases such as test/jdk
>> /java/lang/String/concat/WithSecurityManager.java for all strategies.
>>
>> Testing: tier1-2
>>
>> Thanks!
>>
>> /Claes
>