8323122: AArch64: Increase itable stub size estimate

[linade]

Since JDK-8307352, itable stub size has grown by 20 bytes on linux-aarch64. In particular, the "slop-counted" code increases from 100->120 bytes, where the current estimate is 124 bytes. I haven't found a case where it exceeds the estimate. For now this size is stable across the few linux-aarch64 configurations I ran with. It doesn't vary (for example) by different klass decoding schemes. But I think the idea of the estimate is that we can never know. I propose we increase the estimate to be safe.

Passed hotspot/jtreg/:tier1

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Issue

• JDK-8323122: AArch64: Increase itable stub size estimate (Enhancement - P4)

Reviewers

• Andrew Haley (@theRealAph - Reviewer)
• Evgeny Astigeevich (@eastig - Committer)

Reviewing

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[openjdk]

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[mlbridge]

Webrevs

• 00: Full (4524693d)

[linade]

Can I get a review on this small patch please : )

[openjdk]

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

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

8323122: AArch64: Increase itable stub size estimate

Reviewed-by: aph, eastigeevich

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At the time when this comment was updated there had been 101 new commits pushed to the master branch:

• 1f4474f: 8323726: Serial: Remove unused definitions in Generation
• dd0694b: 8323671: DevKit build gcc libraries contain full paths to source location
• bf813be: 8322279: Generational ZGC: Use ZFragmentationLimit and ZYoungCompactionLimit as percentage instead of multiples
• c84c0ab: 8323637: Capture hotspot replay files in GHA
• f368a0c: 8320328: Restore interrupted flag in ImageIcon.loadImage
• a45b5b4: 8323722: Serial: Remove unused no_gc_in_progress
• 7e0a4ed: 8323101: C2: assert(n->in(0) == nullptr) failed: divisions with zero check should already have bailed out earlier in split-if
• 34f85ee: 8323584: AArch64: Unnecessary ResourceMark in NativeCall::set_destination_mt_safe
• 62fd26f: 8323700: Add fontconfig requirement to building.md for Alpine Linux
• 8c238ed: 8318707: Remove the Java Management Extension (JMX) Management Applet (m-let) feature
• ... and 91 more: https://git.openjdk.org/jdk/compare/37a61720b60a503a958b35c422ca4f2eb06d62fb...master

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[linade]

@theRealAph Do you mind sponsoring this change? Thank you.

/integrate

[openjdk]

@linade
Your change (at version 4524693) is now ready to be sponsored by a Committer.

[shipilev]

I think the patch is fine, but @eastig should also take a look.

[eastig]

lgtm

[eastig]

@linade This is not the first time estimates are updated. JDK-8207343 was implemented to automate vtable/itable stub size calculation. I think it needs improvements. I created JDK-8323741.

[linade]

@eastig Thank you for reviewing. It seems to me that the size calculation can not be easily automated. But the overflow prevention might be, by somehow relocating the stubs (not sure if it's common or possible in hotspot).

[D-D-H]

/sponsor

[openjdk]

Going to push as commit 36f4b34.
Since your change was applied there have been 105 commits pushed to the master branch:

• b363472: 8318227: RISC-V: C2 ConvHF2F
• edc0ebb: 8323745: Missing comma in copyright header in TestScope
• a03eb6d: 8321620: Optimize JImage decompressors
• f5b757c: 8323159: Consider adding some text re. memory zeroing in Arena::allocate
• 1f4474f: 8323726: Serial: Remove unused definitions in Generation
• dd0694b: 8323671: DevKit build gcc libraries contain full paths to source location
• bf813be: 8322279: Generational ZGC: Use ZFragmentationLimit and ZYoungCompactionLimit as percentage instead of multiples
• c84c0ab: 8323637: Capture hotspot replay files in GHA
• f368a0c: 8320328: Restore interrupted flag in ImageIcon.loadImage
• a45b5b4: 8323722: Serial: Remove unused no_gc_in_progress
• ... and 95 more: https://git.openjdk.org/jdk/compare/37a61720b60a503a958b35c422ca4f2eb06d62fb...master

Your commit was automatically rebased without conflicts.

[openjdk]

@D-D-H @linade Pushed as commit 36f4b34.

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