RFR: 8365053: Refresh hotspot precompiled.hpp with headers based on current frequency [v20]

[Aleksey Shipilev]

On Wed, 27 Aug 2025 18:06:30 GMT, Francesco Andreuzzi <duke at openjdk.org> wrote:

>> In this PR I propose to refresh the included headers in hotspot `precompiled.hpp`. The current set of precompiled headers was refreshed in 2018, 7 years ago. I repeated the same operations and measurements after refreshing the set of precompiled headers according to the current usage frequency.
>> 
>> These are the results I observed. Depending on the platform, the improvement is between 10 and 20% in terms of total work (user+sys). The results are in seconds.
>> 
>> 
>> linux-x64 GCC
>> master      real 81.39 user 3352.15 sys 287.49
>> JDK-8365053 real 81.94 user 3030.24 sys 295.82
>> 
>> linux-x64 Clang
>> master      real 43.44 user 2082.93 sys 130.70
>> JDK-8365053 real 38.44 user 1723.80 sys 117.68
>> 
>> linux-aarch64 GCC
>> master      real 1188.08 user 2015.22 sys 175.53
>> JDK-8365053 real 1019.85 user 1667.45 sys 171.86
>> 
>> linux-aarch64 clang
>> master      real 981.77 user 1645.05 sys 118.60
>> JDK-8365053 real 791.96 user 1262.92 sys 101.50
>
> Francesco Andreuzzi has updated the pull request incrementally with one additional commit since the last revision:
> 
>   fix absolute path

Marked as reviewed by shade (Reviewer).

I re-ran the script locally on my Mac, and I think it works without hitches now. There seems to be a tiny bit of variability for generated `precompiled.hpp`, since timing measurements are not exactly precise or consistent across build platforms. But IMO it is not worth diving deeper into.

The build times are still improving, as I tested earlier. 

So, great work all around here, folks. Kudos Francesco for trying multiple approaches and working out the great one! I think we are good to go. If we need any other changes, we can do them as follow-ups.

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PR Review: https://git.openjdk.org/jdk/pull/26681#pullrequestreview-3164025632
PR Comment: https://git.openjdk.org/jdk/pull/26681#issuecomment-3232687434