RFR: 8283276: java/io/ObjectStreamClass/ObjectStreamClassCaching.java fails with various GCs [v2]

[Aleksey Shipilev]

On Wed, 3 Aug 2022 06:24:16 GMT, Peter Levart <plevart at openjdk.org> wrote:

>> This is a continuation of effort from https://github.com/openjdk/jdk/pull/9533 to fix the ObjectStreamClassCaching test which is failing with various GCs != G1. The test class contains 2 test methods:
>> - test2CacheReleaseUnderMemoryPressure - this one was not logically changed at all - just one method was inlined
>> - test1CacheEffectiveness - this one now uses a different strategy which doesn't involve calling System.gc() in order to trigger reference processing in GC which is, as test failures reveal, sometimes to aggressive and triggers processing not only WeakReference(s) but also SoftReference(s). Instead, the test now gradually builds up memory pressure while checking what's happening to two WeakReference(s): ref1 - wrapping a cached ObjectStreamClass instance; and: ref2 - wrapping a new Object() instance. The "effectiveness" of caching is confirmed by verifying that weakly reachable new Object() referent of ref2 is GC-ed earlier than softly reachable ObjectStreamClass referent of ref1.
>> The test now contains several @run(s) with explicitly selected set of GC algorithms: G1, Parallel, ZGC, Shenandoah.
>
> Peter Levart has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add SerialGC variant

Looks good with minor nits. I tested with 100 repeats, and it passes:


$ CONF=linux-x86_64-server-fastdebug make run-test TEST=java/io/ObjectStreamClass/ObjectStreamClassCaching.java JTREG="REPEAT_COUNT=100"

test/jdk/java/io/ObjectStreamClass/ObjectStreamClassCaching.java line 2:

> 1: /*
> 2:  * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.

This update is incorrect, should be:

Suggestion:

 * Copyright (c) 2021, 2022, Oracle and/or its affiliates. All rights reserved.

test/jdk/java/io/ObjectStreamClass/ObjectStreamClassCaching.java line 34:

> 32: 
> 33: /*
> 34:  * @test id=with_G1GC

The test identifiers can be just "G1", "Parallel", "Serial", etc.

test/jdk/java/io/ObjectStreamClass/ObjectStreamClassCaching.java line 72:

> 70:     /**
> 71:      * Test methods execute in same VM and are ordered by name.
> 72:      * We test effectiveness 1st which is sensitive to previous allocations when ZGC is used.

Comment mentions ZGC?

test/jdk/java/io/ObjectStreamClass/ObjectStreamClassCaching.java line 103:

> 101:         assertFalse(
> 102:             ref1.refersTo(null),
> 103:             "Cache lost entry together with WeakReference being cleared although memory was not under pressure"

Style:

Suggestion:

        assertFalse(ref1.refersTo(null),
                    "Cache lost entry together with WeakReference being cleared although memory was not under pressure"

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

PR: https://git.openjdk.org/jdk/pull/9684