8313770: jdk/internal/platform/docker/TestSystemMetrics.java fails on Ubuntu

[caspernorrbin]

Hi everyone,

The test TestSystemMetrics.java sometimes fails on cgroupv2 when comparing read/write I/O metrics (rios/wios) because the expected value doesn't match the one read from the io.stat file. The current approach in this test is somewhat flawed, it reads from the same io.stat file cgroup file twice, once directly and once through jdk.internal.platform.Metrics, and assumes the values should be identical. In practice, this assumption does not hold. Unrelated I/O running in the same cgroup may increment the counter between reads, leading to discrepancies.

The current comparisons have a 25% margin from the original value to account for incidental noise, but this doesn't work well on the I/O operation counters, which can have very small values (sometimes as low as 0), which makes the percentage-based margin useless. As a result, this test is at risk of failing whenever activity happens between the 2 file readings.

For greater reliability, I suggest we should instead check that the value is increasing rather than expecting equality. This is already done for other metrics, such as CPU and memory usage, and more accurately reflects the expected behaviour of the counters. Switching to this check removes the reliance on error margins and results in a more stable and meaningful test.

Testing:

• Repeated runs of TestSystemMetrics.java without any observed failures.
• Oracle tiers 1-5

---

Progress

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• Commit message must refer to an issue

Issue

• JDK-8313770: jdk/internal/platform/docker/TestSystemMetrics.java fails on Ubuntu (Bug - P3)

Reviewers

• Severin Gehwolf (@jerboaa - Reviewer)
• Matthias Baesken (@MBaesken - Reviewer)
• SendaoYan (@sendaoYan - Committer)

Reviewing

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[openjdk]

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

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8313770: jdk/internal/platform/docker/TestSystemMetrics.java fails on Ubuntu

Reviewed-by: sgehwolf, mbaesken, syan

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At the time when this comment was updated there had been 16 new commits pushed to the master branch:

• 3e20a93: 8370156: Fix jpackage IconTest
• be18e7e: 8064922: [macos] Test javax/swing/JTabbedPane/4624207/bug4624207.java fails
• 0744db8: 8367002: Missing compiled exception handler for "recursive" exception
• ... and 13 more: https://git.openjdk.org/jdk/compare/6bf3581bbacc2ed8f6411d23a5ab332376c53c87...master

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[mlbridge]

Webrevs

• 00: Full (1c19d03d)

[jerboaa]

Looks good.

[caspernorrbin]

Thank you all for the reviews!

/integrate

[openjdk]

Going to push as commit aec1388.
Since your change was applied there have been 19 commits pushed to the master branch:

• dcf46a0: 8369658: Client emulation mode sets MaxRAM too late
• 027aea9: 8370325: G1: Disallow GC for TLAB allocation
• ffcb158: 8320677: Printer tests use invalid '@run main/manual=yesno
• ... and 16 more: https://git.openjdk.org/jdk/compare/6bf3581bbacc2ed8f6411d23a5ab332376c53c87...master

Your commit was automatically rebased without conflicts.

[openjdk]

@caspernorrbin Pushed as commit aec1388.

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