RFR: 8261413: Shenandoah: Disable class-unloading in I-U mode

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RFR: 8261413: Shenandoah: Disable class-unloading in I-U mode

Roman Kennke
JDK-8261341 describes a serious problem with I-U mode and class-unloading. Let's disable class-unloading in I-U for now as a workaround.

Testing:
 - [ ] hotspot_gc_shenandoah
 - [ ] tier1 (+UseShenandoahGC +IU)
 - [x] runtime/CreateMirror/ArraysNewInstanceBug.java (+UseShenandoahGC +IU +aggressive) many times in a row w/o failure

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

Commit messages:
 - 8261413: Shenandoah: Disable class-unloading in I-U mode

Changes: https://git.openjdk.java.net/jdk/pull/2477/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2477&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8261413
  Stats: 6 lines in 1 file changed: 6 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2477.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2477/head:pull/2477

PR: https://git.openjdk.java.net/jdk/pull/2477
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Re: RFR: 8261413: Shenandoah: Disable class-unloading in I-U mode

Aleksey Shipilev-5
On Tue, 9 Feb 2021 11:58:58 GMT, Roman Kennke <[hidden email]> wrote:

> JDK-8261341 describes a serious problem with I-U mode and class-unloading. Let's disable class-unloading in I-U for now as a workaround.
>
> Testing:
>  - [ ] hotspot_gc_shenandoah
>  - [ ] tier1 (+UseShenandoahGC +IU)
>  - [x] runtime/CreateMirror/ArraysNewInstanceBug.java (+UseShenandoahGC +IU +aggressive) many times in a row w/o failure

Changes requested by shade (Reviewer).

src/hotspot/share/gc/shenandoah/mode/shenandoahIUMode.cpp line 37:

> 35:
> 36: void ShenandoahIUMode::initialize_flags() const {
> 37:   // See: https://bugs.openjdk.java.net/browse/JDK-8261341

No need for this comment, as the message prints it out.

src/hotspot/share/gc/shenandoah/mode/shenandoahIUMode.cpp line 39:

> 37:   // See: https://bugs.openjdk.java.net/browse/JDK-8261341
> 38:   if (FLAG_IS_CMDLINE(ClassUnloading) && ClassUnloading) {
> 39:     log_warning(gc)("Shenandoah I-U mode forces -XX:-ClassUnloading, for decails, see https://bugs.openjdk.java.net/browse/JDK-8261341");

"Shenandoah I-U mode sets -XX:-ClassUnloading; see JDK-8261341 for details"

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

PR: https://git.openjdk.java.net/jdk/pull/2477
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Re: RFR: 8261413: Shenandoah: Disable class-unloading in I-U mode [v2]

Roman Kennke
In reply to this post by Roman Kennke
> JDK-8261341 describes a serious problem with I-U mode and class-unloading. Let's disable class-unloading in I-U for now as a workaround.
>
> Testing:
>  - [ ] hotspot_gc_shenandoah
>  - [ ] tier1 (+UseShenandoahGC +IU)
>  - [x] runtime/CreateMirror/ArraysNewInstanceBug.java (+UseShenandoahGC +IU +aggressive) many times in a row w/o failure

Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:

  Some comment and output changes as requested by Aleksey

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2477/files
  - new: https://git.openjdk.java.net/jdk/pull/2477/files/491c41c1..e3c1b459

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2477&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2477&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2477.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2477/head:pull/2477

PR: https://git.openjdk.java.net/jdk/pull/2477
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Re: RFR: 8261413: Shenandoah: Disable class-unloading in I-U mode [v2]

Aleksey Shipilev-5
On Tue, 9 Feb 2021 13:10:55 GMT, Roman Kennke <[hidden email]> wrote:

>> JDK-8261341 describes a serious problem with I-U mode and class-unloading. Let's disable class-unloading in I-U for now as a workaround.
>>
>> Testing:
>>  - [ ] hotspot_gc_shenandoah
>>  - [ ] tier1 (+UseShenandoahGC +IU)
>>  - [x] runtime/CreateMirror/ArraysNewInstanceBug.java (+UseShenandoahGC +IU +aggressive) many times in a row w/o failure
>
> Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:
>
>   Some comment and output changes as requested by Aleksey

Marked as reviewed by shade (Reviewer).

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

PR: https://git.openjdk.java.net/jdk/pull/2477
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Re: RFR: 8261413: Shenandoah: Disable class-unloading in I-U mode [v2]

Zhengyu Gu-3
In reply to this post by Roman Kennke
On Tue, 9 Feb 2021 13:13:43 GMT, Roman Kennke <[hidden email]> wrote:

>> JDK-8261341 describes a serious problem with I-U mode and class-unloading. Let's disable class-unloading in I-U for now as a workaround.
>>
>> Testing:
>>  - [ ] hotspot_gc_shenandoah
>>  - [ ] tier1 (+UseShenandoahGC +IU)
>>  - [x] runtime/CreateMirror/ArraysNewInstanceBug.java (+UseShenandoahGC +IU +aggressive) many times in a row w/o failure
>
> Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:
>
>   Some comment and output changes as requested by Aleksey

Marked as reviewed by zgu (Reviewer).

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

PR: https://git.openjdk.java.net/jdk/pull/2477
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Re: RFR: 8261413: Shenandoah: Disable class-unloading in I-U mode [v3]

Roman Kennke
In reply to this post by Roman Kennke
> JDK-8261341 describes a serious problem with I-U mode and class-unloading. Let's disable class-unloading in I-U for now as a workaround.
>
> Testing:
>  - [ ] hotspot_gc_shenandoah
>  - [ ] tier1 (+UseShenandoahGC +IU)
>  - [x] runtime/CreateMirror/ArraysNewInstanceBug.java (+UseShenandoahGC +IU +aggressive) many times in a row w/o failure

Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:

  Don't disable all class-unloading with I-U, disabling concurrent class-unloading is sufficient

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/2477/files
  - new: https://git.openjdk.java.net/jdk/pull/2477/files/e3c1b459..6e99cc98

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=2477&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=2477&range=01-02

  Stats: 3 lines in 1 file changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2477.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2477/head:pull/2477

PR: https://git.openjdk.java.net/jdk/pull/2477
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Re: RFR: 8261413: Shenandoah: Disable class-unloading in I-U mode [v3]

Aleksey Shipilev-5
On Mon, 15 Feb 2021 21:12:53 GMT, Roman Kennke <[hidden email]> wrote:

>> JDK-8261341 describes a serious problem with I-U mode and class-unloading. Let's disable class-unloading in I-U for now as a workaround.
>>
>> Testing:
>>  - [x] hotspot_gc_shenandoah
>>  - [x] tier1 (+UseShenandoahGC +IU)
>>  - [x] runtime/CreateMirror/ArraysNewInstanceBug.java (+UseShenandoahGC +IU +aggressive) many times in a row w/o failure
>
> Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:
>
>   Don't disable all class-unloading with I-U, disabling concurrent class-unloading is sufficient

Marked as reviewed by shade (Reviewer).

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

PR: https://git.openjdk.java.net/jdk/pull/2477
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Integrated: 8261413: Shenandoah: Disable class-unloading in I-U mode

Roman Kennke
In reply to this post by Roman Kennke
On Tue, 9 Feb 2021 11:58:58 GMT, Roman Kennke <[hidden email]> wrote:

> JDK-8261341 describes a serious problem with I-U mode and class-unloading. Let's disable class-unloading in I-U for now as a workaround.
>
> Testing:
>  - [x] hotspot_gc_shenandoah
>  - [x] tier1 (+UseShenandoahGC +IU)
>  - [x] runtime/CreateMirror/ArraysNewInstanceBug.java (+UseShenandoahGC +IU +aggressive) many times in a row w/o failure

This pull request has now been integrated.

Changeset: e2d52ae2
Author:    Roman Kennke <[hidden email]>
URL:       https://git.openjdk.java.net/jdk/commit/e2d52ae2
Stats:     5 lines in 1 file changed: 5 ins; 0 del; 0 mod

8261413: Shenandoah: Disable class-unloading in I-U mode

Reviewed-by: shade, zgu

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PR: https://git.openjdk.java.net/jdk/pull/2477