RFR: 8349713: [leyden] Memory map the cached code file [v4]

[duke]

On Wed, 12 Feb 2025 15:15:01 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> It is visible in profiles for lots of applications that reading the SC cache file at startup costs significantly. On JavacBenchApp example, loading ~25M code requires about 30ms. This is ~1 GB/sec, so it is I/O limited.
>> 
>> We should really mmap the SC cache file to alleviate these costs. Let the actual SC readers (separate threads) to eat the cost of reading from the backing file. 
>> 
>> I was not entirely sure COW for file mappings works correctly on Windows, so I excepted that one.
>> 
>> Additional testing:
>>  - [x] Linux x86_64 server fastdebug, `runtime/cds`
>
> Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Revert "Remove flag, allow all platforms, remove C-heap load"
>   
>   This reverts commit 2f884d8e961eb9ddfe13655a50b7c9edc9758e83.

@shipilev 
Your change (at version f2364f27bc46a497aeccfe6f3e15a4431e18f9bd) is now ready to be sponsored by a Committer.

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PR Comment: https://git.openjdk.org/leyden/pull/34#issuecomment-2654233412