8335007: Inline OopMapCache table

[tstuefe]

OopMapCache uses a (closed hashing) table. The table is C-heap allocated. OopMapCache itself is also C-heap allocated. Since table size is fixed, we can just inline the table to OopMapCache and save one unnecessary pointer-hop on lookup.

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Issue

• JDK-8335007: Inline OopMapCache table (Enhancement - P4)

Reviewers

• Stefan Karlsson (@stefank - Reviewer)
• Coleen Phillimore (@coleenp - Reviewer)
• Aleksey Shipilev (@shipilev - Reviewer)

Reviewing

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[openjdk]

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

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

8335007: Inline OopMapCache table

Reviewed-by: stefank, coleenp, shade

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At the time when this comment was updated there had been 40 new commits pushed to the master branch:

• 79a2301: 8322859: Parallel: Move transform_stack_chunk
• 37e7698: 8335154: jcmd VM.classes -verbose=false does not set verbose to false
• f3b69da: 8335136: Underscore as parameter name in one-parameter functional types fails to compile
• 46b817b: 8333363: ubsan: instanceKlass.cpp: runtime error: member call on null pointer of type 'struct AnnotationArray'
• 0fc5b27: 8332014: since-checker - Fix @ since tags in jdk.jshell
• 9d20b58: 8334328: Reduce object allocation for FloatToDecimal and DoubleToDecimal
• 9bb675f: 8334719: (se) Deferred close of SelectableChannel may result in a Selector doing the final close before concurrent I/O on channel has completed
• 6682305: 8334779: Test compiler/c1/CanonicalizeArrayLength.java is timing out
• 3796fdf: 8328536: javac - crash on unknown type referenced in yield statement
• 07bc523: 8334670: SSLSocketOutputRecord buffer miscalculation
• ... and 30 more: https://git.openjdk.org/jdk/compare/75a2afacc8f5fdec53350b1cb66076cdfeae12f0...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

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[tstuefe]

mac os x64 bug unrelated

[mlbridge]

Webrevs

• 01: Full - Incremental (0bb70c06)
• 00: Full (bb427211)

[stefank]

I'm not a maintainer of this code, but this change looks good to me.

I reacted a little bit when I saw the _size usage in the array expression, thinking that you were using a member variable. It turns out that it is just a constant with a very unconventionally named (for HotSpot) constant. Would anyone object if we/I changed the name of these constants in a follow-up RFE?

[tstuefe]

I'm not a maintainer of this code, but this change looks good to me.

I reacted a little bit when I saw the _size usage in the array expression, thinking that you were using a member variable. It turns out that it is just a constant with a very unconventionally named (for HotSpot) constant. Would anyone object if we/I changed the name of these constants in a follow-up RFE?

I am fine with renaming it to something that does not look like a member. "size" ? "tablesize"? Also, make it a static constexpr? Do we still use enums for constants?

[stefank]

I'm not a maintainer of this code, but this change looks good to me.
I reacted a little bit when I saw the _size usage in the array expression, thinking that you were using a member variable. It turns out that it is just a constant with a very unconventionally named (for HotSpot) constant. Would anyone object if we/I changed the name of these constants in a follow-up RFE?

I am fine with renaming it to something that does not look like a member. "size" ? "tablesize"? Also, make it a static constexpr? Do we still use enums for constants?

The class above uses names the constants like bits_per_entry, so maybe just drop the _ and name it size? (I tend to not like the macro-like names like SIZE)

Most of us try to transition away from enums and instead use explicit type (Not everyone, though). I think there's no consensus around const vs constxpr, but I don't mind seeing things changed to constexpr.

[coleenp]

This change looks fine. If you change _size, you should do the same with _probe_depth. Until recently, there's not a lot of maintenance work in this code, so if you leave it, I'm fine with that.

[coleenp]

If you do change it, change it with this PR please.

[shipilev]

I am okay with doing this without any further renames.

[shipilev]

This is also fine.

[stefank]

Looks good. Thanks!

[tstuefe]

Thanks everyone

/integrate

[openjdk]

Going to push as commit 50dd962.
Since your change was applied there have been 40 commits pushed to the master branch:

• 79a2301: 8322859: Parallel: Move transform_stack_chunk
• 37e7698: 8335154: jcmd VM.classes -verbose=false does not set verbose to false
• f3b69da: 8335136: Underscore as parameter name in one-parameter functional types fails to compile
• 46b817b: 8333363: ubsan: instanceKlass.cpp: runtime error: member call on null pointer of type 'struct AnnotationArray'
• 0fc5b27: 8332014: since-checker - Fix @ since tags in jdk.jshell
• 9d20b58: 8334328: Reduce object allocation for FloatToDecimal and DoubleToDecimal
• 9bb675f: 8334719: (se) Deferred close of SelectableChannel may result in a Selector doing the final close before concurrent I/O on channel has completed
• 6682305: 8334779: Test compiler/c1/CanonicalizeArrayLength.java is timing out
• 3796fdf: 8328536: javac - crash on unknown type referenced in yield statement
• 07bc523: 8334670: SSLSocketOutputRecord buffer miscalculation
• ... and 30 more: https://git.openjdk.org/jdk/compare/75a2afacc8f5fdec53350b1cb66076cdfeae12f0...master

Your commit was automatically rebased without conflicts.

[openjdk]

@tstuefe Pushed as commit 50dd962.

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