RFR: 8339573: Update CodeCacheSegmentSize and CodeEntryAlignment for ARM [v3]

[Boris Ulasevich]

On Tue, 8 Oct 2024 15:11:03 GMT, Evgeny Astigeevich <eastigeevich at openjdk.org> wrote:

> Could you share more data?

This is a simple native benchmark: https://cr.openjdk.org/~bulasevich/AlignBench.cpp

The program tests the performance of code starting from different alignments 
using a generated block of code that primarily consists of NOP (no operation)
and RET (return from subroutine) instructions.

In this experiment (though it may not be meaningful for real-world scenarios) 
on G2 execution time increases with misalignment from the 64-byte boundary, with the 
best performance at exact 64-byte alignment and slower times as the offset grows.

align_64+0: 391.457ms 391.157ms 391.481ms
align_64+4: 392.245ms 392.057ms 391.792ms
align_64+8: 392.154ms 392.962ms 392.65ms
align_64+12: 393.485ms 393.307ms 393.658ms
align_64+16: 394.434ms 394.679ms 394.284ms
align_64+20: 395.681ms 395.709ms 394.843ms
align_64+24: 395.799ms 396.396ms 395.977ms
align_64+28: 397.379ms 397.278ms 397.359ms
align_64+32: 397.677ms 397.82ms 397.95ms
align_64+36: 399.08ms 398.88ms 399.075ms
align_64+40: 399.829ms 400.118ms 399.981ms
align_64+44: 400.916ms 400.747ms 401.241ms
align_64+48: 401.736ms 401.831ms 402.54ms
align_64+52: 402.705ms 402.569ms 402.446ms
align_64+56: 403.718ms 403.822ms 403.535ms
align_64+60: 404.722ms 404.824ms 404.726ms
align_64+64: 390.852ms 390.669ms 391.051ms

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PR Review Comment: https://git.openjdk.org/jdk/pull/20864#discussion_r1792534735