RFR (M): 8078556: Runtime: implement ranges (optionally constraints) for those flags that have them missing

[Jiangli Zhou]

Hi Gerard,

> 
> 
>> I think it would be good to have definitions of
>> DEFAULT_SHARED_READ_WRITE_SIZE = *NOT_LP64(12*M) LP64_ONLY(16*M),* or as
>> constant values above in the file and have the ranges be min = default -
>> 1M and max = default + 1M or something like that.
> 
> I like the approach, but how about we widen up the ranges a bit like so:
> 
> #define DEFAULT_SHARED_READ_WRITE_SIZE  (NOT_LP64(12*M) LP64_ONLY(16*M))
> #define MIN_SHARED_READ_WRITE_SIZE      (DEFAULT_SHARED_READ_WRITE_SIZE/32)
> #define MAX_SHARED_READ_WRITE_SIZE      (DEFAULT_SHARED_READ_WRITE_SIZE*32)
> 
> #define DEFAULT_SHARED_READ_ONLY_SIZE   (NOT_LP64(12*M) LP64_ONLY(16*M))
> #define MIN_SHARED_READ_ONLY_SIZE       (DEFAULT_SHARED_READ_ONLY_SIZE/32)
> #define MAX_SHARED_READ_ONLY_SIZE       (DEFAULT_SHARED_READ_ONLY_SIZE*32)
> 
> #define DEFAULT_SHARED_MISC_DATA_SIZE   (NOT_LP64(2*M) LP64_ONLY(4*M))
> #define MIN_SHARED_MISC_DATA_SIZE       (DEFAULT_SHARED_MISC_DATA_SIZE/16)
> #define MAX_SHARED_MISC_DATA_SIZE       (DEFAULT_SHARED_MISC_DATA_SIZE*16)
> 
> #define DEFAULT_SHARED_MISC_CODE_SIZE   (120*K)
> #define MIN_SHARED_MISC_CODE_SIZE       (DEFAULT_SHARED_MISC_CODE_SIZE/8)
> #define MAX_SHARED_MISC_CODE_SIZE       (DEFAULT_SHARED_MISC_CODE_SIZE*8)
> 

I like the idea of well defined DEFAULT, MIN, and MAX values in a central place. The src/share/vm/memory/metaspaceShared.hpp defines the min values of the shared RO/RW space size. Please make sure the min values are not smaller that those. The Metaspace::global_initialize() (in src/share/vm/memory/metaspace.cpp) calculates the min shared_misc_data and shared_misc_code sizes based on vtable methods. It might not be a good idea to use a static value for those. For the max values of the shared space size, we don’t want to be too restrict as user can specify large number of classes for archiving. The resulting usage of the shared spaces are much larger than the default sizes.

Thanks,
Jiangli