RFR: 8369283: Improve trace logs in safepoint machinery [v6]

[Aleksey Shipilev]

On Wed, 8 Oct 2025 05:44:23 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Aleksey Shipilev has updated the pull request incrementally with two additional commits since the last revision:
>> 
>>  - Put polling exception tracing back with minor reformat
>>  - Touchups
>
> src/hotspot/share/runtime/sharedRuntime.cpp line 683:
> 
>> 681:                        INTPTR_FORMAT ", stub =" INTPTR_FORMAT,
>> 682:                        at_poll_return ? "return" : "loop",
>> 683:                        (intptr_t)pc, (intptr_t)stub);
> 
> Again this seems useful for debugging.

Yes, that makes sense. I initially swatted it away as noise, but it is also a useful debugging/profiling breadcrumb. I put it back, but polished the message a bit, so it fits the whole logging more appropriately. Like this:


[762208335ns] Waiting for 10 threads to block
[762218525ns] Polling page exception: thread = 0x000076b7e458a400, pc = 0x000076b7d3d47167 (loop), stub = 0x000076b7d37851e0
[762220869ns] Polling page exception: thread = 0x000076b7e45810b0, pc = 0x000076b7d3d46de9 (loop), stub = 0x000076b7d37851e0
[762220969ns] Polling page exception: thread = 0x000076b7e4587470, pc = 0x000076b7d3d46de9 (loop), stub = 0x000076b7d37851e0
[762221240ns] Polling page exception: thread = 0x000076b7e45860c0, pc = 0x000076b7d3d46de9 (loop), stub = 0x000076b7d37851e0
[762229325ns] Blocking thread 0x000076b7e458a400
[762229466ns] Blocking thread 0x000076b7e45860c0
[762230628ns] Polling page exception: thread = 0x000076b7e458b8d0, pc = 0x000076b7d3d47167 (loop), stub = 0x000076b7d37851e0
[762220859ns] Polling page exception: thread = 0x000076b7e4584d20, pc = 0x000076b7d3d46de9 (loop), stub = 0x000076b7d37851e0
[762232441ns] Polling page exception: thread = 0x000076b7e457fe30, pc = 0x000076b7d3d46de9 (loop), stub = 0x000076b7d37851e0
[762233403ns] Blocking thread 0x000076b7e45810b0
[762236649ns] Blocking thread 0x000076b7e458b8d0
[762237561ns] Blocking thread 0x000076b7e4587470

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PR Review Comment: https://git.openjdk.org/jdk/pull/27673#discussion_r2413042577