RFR: 8368465: [leyden] Improve precompiler method selection code [v3]

[Aleksey Shipilev]

On Tue, 2 Dec 2025 21:38:57 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> By "blocking" I mean that we have only one AOT compiler thread to load AP4.
>
> May be your change reduced number of AOT compiled nmethod in cache which allow faster processing.
> Please run with `-Xlog:aot+codecache+init=debug -XX:+CITime` for production run to see how many AOT nmethods in AOT cache and how many were loaded/used.

Actually... Now I see we generate, and thus use substantially A2 code! This also aligns with performance data: we have way fewer C1 compilations with this patch.


# ==== Baseline

Create:
  [4.593s][info][precompile] Precompilation for level 1 finished (94 successful out of 94 total)
  [4.604s][info][precompile] Precompilation for level 2 finished (131 successful out of 131 total)
  [4.814s][info][precompile] Precompilation for level 2 finished (1852 successful out of 1852 total)
  [6.035s][info][precompile] Precompilation for level 4 finished (1660 successful out of 1660 total)
  [4.589s][info][precompile] Precompilation for level 5 finished (1660 successful out of 1660 total)

Use:
  Tier1 {speed: 42838.159 bytes/s; standard:  0.014 s, 582 bytes, 135 methods; ...}
  Tier2 {speed: 210303.802 bytes/s; standard:  0.311 s, 63857 bytes, 817 methods; ...}
  Tier3 {speed: 134013.414 bytes/s; standard:  0.035 s, 4685 bytes, 245 methods; ...}
  Tier4 {speed: 69205.374 bytes/s; standard:  0.051 s, 3225 bytes, 13 methods; ...}
  AOT Code T1 {speed: 297580.645 bytes/s; standard:  0.001 s, 369 bytes, 94 methods; ...}
  AOT Code T2 {speed: 5654043.587 bytes/s; standard:  0.042 s, 237861 bytes, 1969 methods; ...}
  AOT Code T4 {speed: 25219362.296 bytes/s; standard:  0.029 s, 737408 bytes, 927 methods; ...}
  AOT Code T5 {speed: 30793594.418 bytes/s; standard:  0.048 s, 1474270 bytes, 1658 methods; ...}


# ==== Patched

Create:
  [3.984s][info][precompile] Precompilation for level 1 finished (311 successful out of 311 total)
  [4.382s][info][precompile] Precompilation for level 2 finished (2752 successful out of 2752 total)
  [4.383s][info][precompile] Precompilation for level 3 finished (0 successful out of 0 total)
  [5.392s][info][precompile] Precompilation for level 4 finished (1641 successful out of 1641 total)
  [3.972s][info][precompile] Precompilation for level 5 finished (1641 successful out of 1641 total)

Use:
  Tier1 {speed:  0.000 bytes/s; standard:  0.000 s, 0 bytes, 0 methods; ...
  Tier2 {speed: 579987.470 bytes/s; standard:  0.026 s, 15526 bytes, 44 methods; ...
  Tier3 {speed: 181499.273 bytes/s; standard:  0.026 s, 4761 bytes, 254 methods; ...
  Tier4 {speed: 77265.133 bytes/s; standard:  0.027 s, 2087 bytes, 12 methods; ...
  AOT Code T1 {speed: 432360.583 bytes/s; standard:  0.002 s, 942 bytes, 228 methods; ...
  AOT Code T2 {speed: 6664604.248 bytes/s; standard:  0.042 s, 281287 bytes, 2735 methods; ...
  AOT Code T4 {speed: 26296881.658 bytes/s; standard:  0.026 s, 682331 bytes, 924 methods; ...
  AOT Code T5 {speed: 33814172.284 bytes/s; standard:  0.042 s, 1430045 bytes, 1632 methods; ...


So I have changed something in selection code that takes on more A2 compiles, profitably.  Have not yet confirmed if preload order has any effect on top of that. Investigating...

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PR Review Comment: https://git.openjdk.org/leyden/pull/99#discussion_r2584978192