RFR: 8349713: [leyden] Memory map the cached code file [v2]
Aleksey Shipilev
shade at openjdk.org
Tue Feb 11 18:45:33 UTC 2025
On Mon, 10 Feb 2025 16:36:04 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 with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:
>
> - Merge branch 'premain' into JDK-8349713-mmap-sccache
> - Fix
Any other opinions about this? I would like to integrate this to reap some startup benefits :)
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PR Comment: https://git.openjdk.org/leyden/pull/34#issuecomment-2651695745
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