RFR: 8344068: Windows x86-64: Out of CodeBuffer space when generating final stubs

[Andrew Haley]

On Tue, 3 Dec 2024 18:48:38 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> Scratch that. I see call stack in the bug report. It is indeed final stubs for upcall stub when ZGC is enabled.
>> Should we increase ZGC_ONLY(+20000) value instead?
>
> ZGC save/restores XMM registers regardless OS: [x86/gc/z/zBarrierSetAssembler_x86.cpp#L70](https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/x86/gc/z/zBarrierSetAssembler_x86.cpp#L70)

I spent a while reading the dumps of final stubs. I can account for 10k additional for XMM stubs in final on Windows. This takes it to the edge.

It may well be that this is really a ZGC thing, but with ZGC on Linux we get nowhere near the limit. I think there is about 20k difference between Linux and Windows with ZGC enabled. I can't account for all of it, though.

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PR Review Comment: https://git.openjdk.org/jdk/pull/22516#discussion_r1871450927