8266891: Provide a switch to force the class space to a specific location #3969

tstuefe · 2021-05-11T08:52:55Z

To test compressed Klass pointer encoding and other metaspace interna, it would be nice to be able to force location of the class space to a specific location. This would help with analysis of problems like JDK-8261552 or JDK-8265705 - errors in Klass* encoding/decoding which managed to stay unnoticed for an astonishingly long time.

For simplicity, it would be sufficient to only have this ability if CDS is disabled (Xshare=off), since CCS allocation is tied to CDS location otherwise and that would be more diffictult to disentangle.

Progress

Change must not contain extraneous whitespace
Commit message must refer to an issue
Change must be properly reviewed

Issue

JDK-8266891: Provide a switch to force the class space to a specific location

Reviewers

Ioi Lam (@iklam - Reviewer) ⚠️ Review applies to 532a728
Coleen Phillimore (@coleenp - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk pull/3969/head:pull/3969
$ git checkout pull/3969

Update a local copy of the PR:
$ git checkout pull/3969
$ git pull https://git.openjdk.java.net/jdk pull/3969/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 3969

View PR using the GUI difftool:
$ git pr show -t 3969

Using diff file

Download this PR as a diff file:
https://git.openjdk.java.net/jdk/pull/3969.diff

bridgekeeper · 2021-05-11T08:53:51Z

👋 Welcome back stuefe! 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 · 2021-05-11T08:56:21Z

@tstuefe 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 · 2021-05-11T11:48:12Z

Webrevs

01: Full - Incremental (2d962a24)
00: Full (532a7287)

iklam

LGTM

openjdk · 2021-05-15T03:08:34Z

@tstuefe 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:

8266891: Provide a switch to force the class space to a specific location

Reviewed-by: iklam, coleenp

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 445 new commits pushed to the master branch:

159cb6f: 8268083: JDK-8267706 breaks bin/idea.sh on a Mac
8158b82: 8268327: Upstream: 8268169: The system lookup can not find stdio functions such as printf on Windows 10
6843576: 8268227: java/foreign/TestUpcall.java still times out
2717fcb: 8232948: javac -h should mangle the overload argument signature
89da202: 8266159: macOS ARM + Metal pipeline shows artifacts on Swing Menu with Java L&F
61ab4b9: 8267564: JDK-8252971 causes SPECjbb2015 socket exceptions on Windows when MKS is installed
00c88f7: 8266918: merge_stack in check_code.c add NULL check
8105478: 8268165: AsyncLogging will crash if rotate() fails
fd91b2a: 8265440: IGV: make node selection more visible
81bad59: 8257774: G1: Trigger collect when free region count drops below threshold to prevent evacuation failures
... and 435 more: https://git.openjdk.java.net/jdk/compare/ff77ca8bd41ece778cf6f1af6dd1b7a7dfc50eab...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.

coleenp

This seems good. Small comment. Were you going to add a test or did you want this to test manually?

coleenp · 2021-05-27T00:44:09Z

src/hotspot/share/memory/metaspace.cpp

+    // the given address. This is a debug-only feature aiding tests. Due to the ASLR lottery
+    // this may fail, in which case the VM will exit after printing an appropiate message.
+    // Tests using this switch should cope with that.
+    if (!FLAG_IS_DEFAULT(CompressedClassSpaceBaseAddress) && CompressedClassSpaceBaseAddress != 0) {


Don't you just have to test if CompressedClassSpaceBaseAddress != 0 , since that's the default if not set?

Makes sense, I'll change that.

tstuefe · 2021-06-08T12:12:37Z

This seems good. Small comment. Were you going to add a test or did you want this to test manually?

Thank you Coleen. I'll add a test in a follow up RFE.

coleenp

This update looks good. Could you do a paranoid short test run (or have you done?) before integrating? Thanks!
Never mind, I see the git build actions were successful.

tstuefe · 2021-06-09T04:04:35Z

This update looks good. Could you do a paranoid short test run (or have you done?) before integrating? Thanks!
Never mind, I see the git build actions were successful.

Thank you Coleen!

/integrate

openjdk · 2021-06-09T04:06:10Z

@tstuefe Since your change was applied there have been 460 commits pushed to the master branch:

2cc1977: 8268424: JFR tests fail due to GC cause 'G1 Preventive Collection' not in the valid causes after JDK-8257774
58a59e3: 8240997: Remove more "hack" word in security codes
1c3932f: 8264766: ClassCastException during template compilation (Variable cannot be cast to Param)
f6f82c3: 8266421: Deadlock in Sound System
bcaa2cb: 8264144: Add handling of "--about-url" CLI parameter for RPM/DEB packages
ae16052: 8268088: Clarify Method::clear_jmethod_ids() related comments in ClassLoaderData::~ClassLoaderData()
5ad4a91: 8268127: Shenandoah: Heap size may be too small for region to align to large page size
7a37816: 8264866: Remove unneeded WorkArounds.isAutomaticModule
51e8201: 8267764: jpackage cannot handle window screensaver files when EXE renamed as SCR
f9b593d: 8266748: Move modifiers code to Signatures.java
... and 450 more: https://git.openjdk.java.net/jdk/compare/ff77ca8bd41ece778cf6f1af6dd1b7a7dfc50eab...master

Your commit was automatically rebased without conflicts.

Pushed as commit c9dbc4f.

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

start

532a728

openjdk bot added the hotspot-runtime hotspot-runtime-dev@openjdk.org label May 11, 2021

tstuefe marked this pull request as ready for review May 11, 2021 11:42

openjdk bot added the rfr Pull request is ready for review label May 11, 2021

iklam approved these changes May 15, 2021

View reviewed changes

openjdk bot added the ready Pull request is ready to be integrated label May 15, 2021

coleenp approved these changes May 27, 2021

View reviewed changes

Feedback Coleen

2d962a2

coleenp approved these changes Jun 8, 2021

View reviewed changes

openjdk bot closed this Jun 9, 2021

openjdk bot added integrated Pull request has been integrated and removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Jun 9, 2021

tstuefe deleted the JDK-8266891-Provider-a-switch-to-force-the-class-space-to-a-specific-location branch June 29, 2021 05:34

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

8266891: Provide a switch to force the class space to a specific location #3969

8266891: Provide a switch to force the class space to a specific location #3969

tstuefe commented May 11, 2021 •

edited by openjdk bot

Loading

bridgekeeper bot commented May 11, 2021

openjdk bot commented May 11, 2021

mlbridge bot commented May 11, 2021 •

edited

Loading

iklam left a comment

openjdk bot commented May 15, 2021 •

edited

Loading

coleenp left a comment

coleenp May 27, 2021

tstuefe Jun 8, 2021

tstuefe commented Jun 8, 2021

coleenp left a comment •

edited

Loading

tstuefe commented Jun 9, 2021

openjdk bot commented Jun 9, 2021

8266891: Provide a switch to force the class space to a specific location #3969

8266891: Provide a switch to force the class space to a specific location #3969

Conversation

tstuefe commented May 11, 2021 • edited by openjdk bot Loading

Progress

Issue

Reviewers

Reviewing

bridgekeeper bot commented May 11, 2021

openjdk bot commented May 11, 2021

mlbridge bot commented May 11, 2021 • edited Loading

Webrevs

iklam left a comment

Choose a reason for hiding this comment

openjdk bot commented May 15, 2021 • edited Loading

coleenp left a comment

Choose a reason for hiding this comment

coleenp May 27, 2021

Choose a reason for hiding this comment

tstuefe Jun 8, 2021

Choose a reason for hiding this comment

tstuefe commented Jun 8, 2021

coleenp left a comment • edited Loading

Choose a reason for hiding this comment

tstuefe commented Jun 9, 2021

openjdk bot commented Jun 9, 2021

tstuefe commented May 11, 2021 •

edited by openjdk bot

Loading

mlbridge bot commented May 11, 2021 •

edited

Loading

openjdk bot commented May 15, 2021 •

edited

Loading

coleenp left a comment •

edited

Loading