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

[dholmes-ora]

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

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change requires CSR request JDK-8345956 to be approved

Issues

• JDK-8345955: Deprecate the UseOprofile flag with a view to removing the legacy oprofile support in the VM (Enhancement - P4)
• JDK-8345956: Deprecate the UseOprofile flag with a view to removing the legacy oprofile support in the VM (CSR)

Reviewers

• Ioi Lam (@iklam - Reviewer)
• Aleksey Shipilev (@shipilev - Reviewer)

Reviewing

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$ git checkout pull/22674

Update a local copy of the PR:
$ git checkout pull/22674
$ git pull https://git.openjdk.org/jdk.git pull/22674/head

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$ git pr checkout 22674

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[bridgekeeper]

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[openjdk]

@dholmes-ora This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

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

Reviewed-by: iklam, shade

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 29 new commits pushed to the master branch:

• ec219ae: 8346039: [BACKOUT] - [C1] LIR Operations with one input should be implemented as LIR_Op1
• 05c5678: 8345959: Make JVM_IsStaticallyLinked JVM_LEAF
• 64fad1c: 8345797: Update copyright year to 2024 for client-libs in files where it was missed
• ddf0461: 8345799: Update copyright year to 2024 for core-libs in files where it was missed
• cbab40b: 8345683: Remove special flags for files compiled for static libraries
• 08bdeed: 8345269: Fix -Wzero-as-null-pointer-constant warnings in ppc code
• e4a34e9: 8345616: Unnecessary Hashtable usage in javax.swing.text.html.parser.Element
• cce5808: 8345421: (bf) Create specific test for temporary direct buffers and the buffer size limit
• cf0e1aa: 8345335: Add excluded jdk_foreign tests to manual group
• 2c4567a: 8342651: Refactor array constant to use an array of jbyte
• ... and 19 more: https://git.openjdk.org/jdk/compare/c6317191e323e27cde61b5ed3c23d1a230053969...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[openjdk]

@dholmes-ora The following label will be automatically applied to this pull request:

• hotspot-runtime

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

[mlbridge]

Webrevs

• 00: Full (d969b1ad)

[iklam]

The UseOprofile flag is still used in linux_wrap_code(). Should we remove this function as well?

jdk/src/hotspot/os/linux/os_linux.cpp

Lines 2835 to 2865 in c631719

	void linux_wrap_code(char* base, size_t size) {
	static volatile jint cnt = 0;
	static_assert(sizeof(off_t) == 8, "Expected Large File Support in this file");
	if (!UseOprofile) {
	return;
	}
	char buf[PATH_MAX+1];
	int num = Atomic::add(&cnt, 1);
	snprintf(buf, sizeof(buf), "%s/hs-vm-%d-%d",
	os::get_temp_directory(), os::current_process_id(), num);
	unlink(buf);
	int fd = ::open(buf, O_CREAT | O_RDWR, S_IRWXU);
	if (fd != -1) {
	off_t rv = ::lseek(fd, size-2, SEEK_SET);
	if (rv != (off_t)-1) {
	if (::write(fd, "", 1) == 1) {
	mmap(base, size,
	PROT_READ|PROT_WRITE|PROT_EXEC,
	MAP_PRIVATE|MAP_FIXED|MAP_NORESERVE, fd, 0);
	}
	}
	::close(fd);
	unlink(buf);
	}
	}

[dholmes-ora]

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

[iklam]

LGTM

[dholmes-ora]

Thanks for the review @iklam !

[dholmes-ora]

Thanks for the review @shipilev !

/integrate

[openjdk]

Going to push as commit ceb4366.
Since your change was applied there have been 32 commits pushed to the master branch:

• 72c59de: 8345876: Update nativeAddAtIndex comment to match the code
• 75cfb64: 8310691: [REDO] [vectorapi] Refactor VectorShuffle implementation
• 4da6fd4: 8345423: Shenandoah: Parallelize concurrent cleanup
• ec219ae: 8346039: [BACKOUT] - [C1] LIR Operations with one input should be implemented as LIR_Op1
• 05c5678: 8345959: Make JVM_IsStaticallyLinked JVM_LEAF
• 64fad1c: 8345797: Update copyright year to 2024 for client-libs in files where it was missed
• ddf0461: 8345799: Update copyright year to 2024 for core-libs in files where it was missed
• cbab40b: 8345683: Remove special flags for files compiled for static libraries
• 08bdeed: 8345269: Fix -Wzero-as-null-pointer-constant warnings in ppc code
• e4a34e9: 8345616: Unnecessary Hashtable usage in javax.swing.text.html.parser.Element
• ... and 22 more: https://git.openjdk.org/jdk/compare/c6317191e323e27cde61b5ed3c23d1a230053969...master

Your commit was automatically rebased without conflicts.

[openjdk]

@dholmes-ora Pushed as commit ceb4366.

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