8290466: Default to --with-source-date=current to avoid unmodified Hotspot recompilation

[shipilev]

See the bug for symptoms and rationale.

In short, after JDK-8288396 moved the timestamp to CFLAGS_VM_VERSION macro, which changes with every build, we get Hotspot recompilation every time, even when Hotspot is not modified.

I believe current behavior is correct for --with-source-date=updated (current default): you do Hotspot build, you get updated build timestamp, which forces recompilation of affected compilation units, relinkage, re-creation of jmods/jimage. The way out is to switch to --with-source-date=current, which would only get the build timestamp at configure time.

CIs and build farms are likely reconfiguring before every build anyway, so their behavior is unlikely to be affected. But this switch definitely improves the day-to-day OpenJDK development work: it saves >50 seconds on every make for my machine, see below.

Back-to-back unmodified build before:

$ CONF=linux-x86_64-server-release time make hotspot
Building target 'hotspot' in configuration 'linux-x86_64-server-release'
Finished building target 'hotspot' in configuration 'linux-x86_64-server-release'

39.03user 10.97system 0:56.89elapsed 87%CPU (0avgtext+0avgdata 2048944maxresident)k
363616inputs+4108072outputs (484major+1100154minor)pagefaults 0swaps

$ CONF=linux-x86_64-server-release time make hotspot
Building target 'hotspot' in configuration 'linux-x86_64-server-release'
Finished building target 'hotspot' in configuration 'linux-x86_64-server-release'

38.18user 9.02system 0:49.18elapsed 95%CPU (0avgtext+0avgdata 2048788maxresident)k
40inputs+4101112outputs (0major+1100077minor)pagefaults 0swaps

Back-to-back unmodified build after:

$ CONF=linux-x86_64-server-release time make hotspot
Building target 'hotspot' in configuration 'linux-x86_64-server-release'
Finished building target 'hotspot' in configuration 'linux-x86_64-server-release'

2.15user 0.22system 0:02.59elapsed 91%CPU (0avgtext+0avgdata 49480maxresident)k
0inputs+176outputs (0major+55506minor)pagefaults 0swaps

$ CONF=linux-x86_64-server-release time make hotspot
Building target 'hotspot' in configuration 'linux-x86_64-server-release'
Finished building target 'hotspot' in configuration 'linux-x86_64-server-release'

2.18user 0.14system 0:02.46elapsed 94%CPU (0avgtext+0avgdata 49332maxresident)k

---

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Issue

• JDK-8290466: Default to --with-source-date=current to avoid unmodified Hotspot recompilation

Reviewers

• Erik Joelsson (@erikj79 - Reviewer) ⚠️ Review applies to 0f0163f5
• Magnus Ihse Bursie (@magicus - Reviewer) ⚠️ Review applies to 0f0163f5

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[mlbridge]

Webrevs

• 01: Full - Incremental (10ab14aa)
• 00: Full (0f0163f5)

[openjdk]

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After integration, the commit message for the final commit will be:

8290466: Default to --with-source-date=current to avoid unmodified Hotspot recompilation

Reviewed-by: erikj, ihse

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[shipilev]

Any other opinions?

[shipilev]

@magicus -- you are good with this, or?

[magicus]

Sorry for the slow response, I'm on vacation. 😎

This looks good to me. Just update the default value in the help text as well:

      [how to set SOURCE_DATE_EPOCH ('updated', 'current', 'version' a timestamp or an ISO-8601 date) @<:@current/value of SOURCE_DATE_EPOCH@:>@])],

(github does not allow me to comment on it since it's too far away from any changed lines in the PR)

[shipilev]

Sorry for the slow response, I'm on vacation.

Ah. I seen a few replies from you assumed you are back.

      [how to set SOURCE_DATE_EPOCH ('updated', 'current', 'version' a timestamp or an ISO-8601 date) @<:@current/value of SOURCE_DATE_EPOCH@:>@])],

Good spot, fixed in new commit.

[shipilev]

Entering the week with faster builds.

/integrate

[openjdk]

Going to push as commit d9cb410.
Since your change was applied there have been 12 commits pushed to the master branch:

• acbe093: 8291559: x86: compiler/vectorization/TestReverseBitsVector.java fails
• 32d410a: 8290868: NMT: MallocSiteTable statistics improvements
• 3579024: 8288904: Incorrect memory ordering in UL
• 470c0eb: 8290740: Catalog not used when the handler is null
• dd9bd31: 8289688: jfr command hangs when it processes invalid file
• 8179a19: 8290243: move seeTagToContent from HtmlDocletWriter to TagletWriterImpl
• 15943e4: 8282666: nsk/jvmti/PopFrame/popframe004 failed with: TEST FAILED: 30 JVMTI events were generated by the function PopFrame()
• 0bcf176: 6227536: KeyGenerator.init() methods do not throw IllegalArgumentException for keysize == 0
• cc2861a: 8290901: Reduce use of -source in langtools tests
• 64a1a08: 8289647: AssertionError during annotation processing of record related tests
• ... and 2 more: https://git.openjdk.org/jdk/compare/18cd16d2eae2ee624827eb86621f3a4ffd98fe8c...master

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev Pushed as commit d9cb410.

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