RFR: 8345955: Deprecate the UseOprofile flag with a view to removing the legacy oprofile support in the VM

[David Holmes]

On Wed, 11 Dec 2024 00:46:50 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> Please review this simple change to deprecate the `UseOprofile` flag in JDK 25, with a view to obsoleting it in JDK 26.
>> 
>> The VM has supported the Linux OProfile profiler since 2005, however to work properly with OProfile's Linux kernel module (ref lookup_dcookie()), the VM has to change the way compiled code memory is mapped. That is done under the control of the UseOprofile flag (default false). Since 2012 OProfile has not needed the kernel module, and it was removed from the kernel in 2021. Consequently this special code and the UseOprofile flag are not needed.
>> 
>> Could I also get a Reviewer for the CSR request please.
>> 
>> Testing: tiers 1-3 (sanity)
>> 
>> Thanks
>
> The `UseOprofile` flag is still used in linux_wrap_code(). Should we remove this function as well?
> 
> https://github.com/openjdk/jdk/blob/c6317191e323e27cde61b5ed3c23d1a230053969/src/hotspot/os/linux/os_linux.cpp#L2835-L2865

@iklam at this stage we are only deprecating the flag to prepare for the code removal in JDK 26.

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PR Comment: https://git.openjdk.org/jdk/pull/22674#issuecomment-2533365853