8290834: Improve potentially confusing documentation on collection of profiling information by TheShermanTanker · Pull Request #9598 · openjdk/jdk

TheShermanTanker · 2022-07-21T18:36:43Z

Documentation on the MethodData object incorrectly states that it is used when profiling in tiers 0 and 1, when it only does so for tier 0 (Interpreter) and tier 3, while tier 1 (Fully optimizing C1) does not collect any profile data at all. Additionally, the description for the different execution tiers is slightly confusing. This cleanup attempts to slightly better clarify how profiling is tied together between the Interpreter and C1, explain what MDO is an abbreviation for (MethodData object), and corrects the documentation for MethodData as well.

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Issue

JDK-8290834: Improve potentially confusing documentation on collection of profiling information

Reviewers

Tobias Hartmann (@TobiHartmann - Reviewer)
Vladimir Kozlov (@vnkozlov - Reviewer)
Dean Long (@dean-long - Reviewer)

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Update a local copy of the PR:
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$ git pull https://git.openjdk.org/jdk pull/9598/head

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$ git pr checkout 9598

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bridgekeeper · 2022-07-21T18:36:50Z

👋 Welcome back jwaters! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2022-07-21T18:42:39Z

@TheShermanTanker The following label will be automatically applied to this pull request:

hotspot

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 · 2022-07-21T18:46:40Z

Webrevs

src/hotspot/share/compiler/compilationPolicy.hpp

src/hotspot/share/oops/methodData.hpp

dean-long · 2022-07-22T01:14:47Z

/label hotspot-compiler

openjdk · 2022-07-22T01:15:13Z

@dean-long
The hotspot-compiler label was successfully added.

dean-long · 2022-07-22T08:51:55Z

C1 uses ciMethod::ensure_method_data(), which calls Method::build_interpreter_method_data(), to create an MDO if one wasn't already created by the interpreter. So the name build_interpreter_method_data() is a bit misleading, because C1 will use the same MDO as the interpreter.

I also found a comment in c1_globals.hpp about C1UpdateMethodData that mentions tier1. I think the comment should be changed to say tier3.

…o profile

openjdk · 2022-07-22T11:33:46Z

⚠️ @TheShermanTanker This pull request contains merges that bring in commits not present in the target repository. Since this is not a "merge style" pull request, these changes will be squashed when this pull request in integrated. If this is your intention, then please ignore this message. If you want to preserve the commit structure, you must change the title of this pull request to Merge <project>:<branch> where <project> is the name of another project in the OpenJDK organization (for example Merge jdk:master).

src/hotspot/share/compiler/compilationPolicy.hpp

vnkozlov · 2022-07-22T18:36:54Z

Please note. CI (compiler interface) and its API (ciMethod*) is used by JIT compilers C1 and C2 only during compilation.
Compilers (C1 and C2) can create MDO (through CI) if it is missed but they don't update data in it.
Only Interpreter and tier 3 (profiling) compiled code produced by C1 updates MDO. It does it directly without CI.

vnkozlov · 2022-07-22T18:39:49Z

@dean-long posted his comment before I finished my :)
But we are saying the same thing.

TheShermanTanker · 2022-07-23T07:56:43Z

Please note. CI (compiler interface) and its API (ciMethod*) is used by JIT compilers C1 and C2 only during compilation. Compilers (C1 and C2) can create MDO (through CI) if it is missed but they don't update data in it. Only Interpreter and tier 3 (profiling) compiled code produced by C1 updates MDO. It does it directly without CI.

Ah, my mistake. I'll fix the issue asap

mlbridge · 2022-07-24T12:22:54Z

Mailing list message from Kandu, Rahul on hotspot-compiler-dev:

-----Original Message-----
From: hotspot-compiler-dev <hotspot-compiler-dev-retn at openjdk.org> On Behalf Of Julian Waters
Sent: Saturday, July 23, 2022 7:00 AM
To: hotspot-dev at openjdk.org; hotspot-compiler-dev at openjdk.org
Subject: Re: RFR: 8290834: Improve potentially confusing documentation on collection of profiling information [v6]

On Fri, 22 Jul 2022 18:17:26 GMT, Dean Long <dlong at openjdk.org> wrote:

Julian Waters has updated the pull request incrementally with one additional commit since the last revision:

New changes

src/hotspot/share/compiler/compilationPolicy.hpp line 47:

45: * for the interpreter and ciMethod::ensure_method_data, ciMethod.cpp for C1), and interacts
46: * with C1 and C2 via the compiler interface. It is updated periodically as more profiling
47: * information is gathered, directly in the case of the interpreter and through ciMethodData

This is still a bit misleading. The information flow between MethodData and ciMethodData is one-way. Only MethodData are updated by the interpreter or generated code. ciMethodData is just a read-only snapshot used during compilation.

Revised

-------------

PR: https://git.openjdk.org/jdk/pull/9598

TobiHartmann

Looks good to me.

TobiHartmann · 2022-07-25T12:55:35Z

/reviewers 2

openjdk · 2022-07-25T12:57:08Z

@TheShermanTanker 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:

8290834: Improve potentially confusing documentation on collection of profiling information

Reviewed-by: thartmann, kvn, dlong

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 17 new commits pushed to the master branch:

7c3cfd1: 8290557: tools/jpackage/share/AddLauncherTest.java#id1 failed with "ERROR: Failed: Check icon file"
0ca74f5: 8289659: Refactor I/O stream copying to use InputStream.readAllBytes in X509CertPath
1e270ea: 8290780: AArch64: Crash in c2 nmethod running RunThese30M.java
b17269a: 8290959: Consistently use "grey" instead of "gray" in GC code
350808a: 8290459: Remove unused GCCause enums
d0c365a: 8170794: [macosx] Error when using setDesktopManager on a JDesktopPane on MacOS X with Look and Feel Aqua
80dc6ce: 8290730: compiler/vectorization/TestAutoVecIntMinMax.java failed with "IRViolationException: There were one or multiple IR rule failures."
228e8e9: 8290700: Optimize AArch64 nmethod entry barriers
852e71d: 8290870: NMT: Increase MallocSiteTable size and allocate it only when needed
0599a05: 8290900: Build failure with Clang 14+ due to function warning attribute
... and 7 more: https://git.openjdk.org/jdk/compare/7841e5cc387ba595f73f40b3a0d00d7e36df15ea...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.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@TobiHartmann, @vnkozlov, @dean-long) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

openjdk · 2022-07-25T12:57:33Z

@TobiHartmann
The total number of required reviews for this PR (including the jcheck configuration and the last /reviewers command) is now set to 2 (with at least 1 Reviewer, 1 Author).

vnkozlov

Good.

TheShermanTanker · 2022-07-25T17:27:31Z

Thanks all for the reviews!

TheShermanTanker · 2022-07-25T17:29:35Z

/integrate

openjdk · 2022-07-25T17:29:47Z

@TheShermanTanker
Your change (at version a6b7501) is now ready to be sponsored by a Committer.

openjdk · 2022-07-25T17:33:17Z

@TheShermanTanker
Your change (at version a6b7501) is now ready to be sponsored by a Committer.

dean-long · 2022-07-25T22:45:00Z

/sponsor

openjdk · 2022-07-25T22:46:30Z

Going to push as commit 0ca5cb1.
Since your change was applied there have been 17 commits pushed to the master branch:

7c3cfd1: 8290557: tools/jpackage/share/AddLauncherTest.java#id1 failed with "ERROR: Failed: Check icon file"
0ca74f5: 8289659: Refactor I/O stream copying to use InputStream.readAllBytes in X509CertPath
1e270ea: 8290780: AArch64: Crash in c2 nmethod running RunThese30M.java
b17269a: 8290959: Consistently use "grey" instead of "gray" in GC code
350808a: 8290459: Remove unused GCCause enums
d0c365a: 8170794: [macosx] Error when using setDesktopManager on a JDesktopPane on MacOS X with Look and Feel Aqua
80dc6ce: 8290730: compiler/vectorization/TestAutoVecIntMinMax.java failed with "IRViolationException: There were one or multiple IR rule failures."
228e8e9: 8290700: Optimize AArch64 nmethod entry barriers
852e71d: 8290870: NMT: Increase MallocSiteTable size and allocate it only when needed
0599a05: 8290900: Build failure with Clang 14+ due to function warning attribute
... and 7 more: https://git.openjdk.org/jdk/compare/7841e5cc387ba595f73f40b3a0d00d7e36df15ea...master

Your commit was automatically rebased without conflicts.

openjdk · 2022-07-25T22:46:48Z

@dean-long @TheShermanTanker Pushed as commit 0ca5cb1.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

Better clarify documentation

478ca61

openjdk bot changed the title ~~8290834~~ 8290834: Improve potentially confusing documentation on collection of profiling information Jul 21, 2022

openjdk bot added the rfr Pull request is ready for review label Jul 21, 2022

TheShermanTanker added 2 commits July 22, 2022 02:39

Minor comment cleanup

f116fd8

Update compilationPolicy.hpp

57d60a6

openjdk bot added the hotspot hotspot-dev@openjdk.org label Jul 21, 2022

dean-long reviewed Jul 22, 2022

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openjdk bot added the hotspot-compiler hotspot-compiler-dev@openjdk.org label Jul 22, 2022

Correct comment with respect to review

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TheShermanTanker added 2 commits July 22, 2022 19:30

Merge remote-tracking branch 'upstream/master' into profile

947aeaa

Merge branch 'profile' of https://github.com/TheShermanTanker/jdk int…

fba6dd2

…o profile

TheShermanTanker added 3 commits July 22, 2022 19:40

Rectify incorrect Tier 1 message for C1UpdateMethodData

f6dc352

Quick fix

bf83804

New changes

c48d67f

dean-long reviewed Jul 22, 2022

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Fixup

a6b7501

TobiHartmann approved these changes Jul 25, 2022

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openjdk bot added the ready Pull request is ready to be integrated label Jul 25, 2022

openjdk bot removed the ready Pull request is ready to be integrated label Jul 25, 2022

vnkozlov approved these changes Jul 25, 2022

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openjdk bot added the ready Pull request is ready to be integrated label Jul 25, 2022

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dean-long approved these changes Jul 25, 2022

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openjdk bot closed this Jul 25, 2022

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review sponsor Pull request is ready to be sponsored labels Jul 25, 2022

TheShermanTanker deleted the profile branch July 26, 2022 05:46

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