RFR: 8372701: Randomized profile counters [v2]

[Andrew Haley]

On Mon, 15 Dec 2025 11:13:27 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> To your example: indeed, there is no recourse in case when really-polymorphic site is accidentally looking monomorphic due to code behavior artifacts: e.g. no one came with rare type just yet. But IMO that does not mean we would be opening more performance trap-doors when some code _did_ come with the rare type, especially if it is easy to handle.

Thanks for this input, it helps a lot.

How cheap it is always to update type profile counters depends on how many threads are racily updating them. But it's easy to move type-profiling code from behind the random step to in front of it, so I'll make that change.

> The fact that some of your horses might have bolted, does not give you a good reason to open the barn door a bit wider

Agree totally in principle, but that analogy only works if the cost of closing the door is near-zero. It may well be so, we'll see.

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PR Comment: https://git.openjdk.org/jdk/pull/28541#issuecomment-3655712779