8294751: Zero: Allow larger default heaps

[shipilev]

Zero is currently defaulting to MaxRAM=1G on all machines. It is set in compiler_globals.pd under #if !defined(COMPILER1) && !defined(COMPILER2) && !INCLUDE_JVMCI.

Zero supports lots of GCs, and there is little sense to penalize it unnecessarily with too small heaps. After JDK-8292847, this would allow G1 with reasonable heap size on most machines.

Motivational improvements, SPECjvm2008:serial:

# Baseline, G1
Serial.test  thrpt   10  1619.863 ± 16.694  ops/s

# Baseline, Serial
Serial.test  thrpt   10  1094.438 ± 20.425  ops/s

# Patched, G1
Serial.test  thrpt   10  1623.090 ± 17.553  ops/s

# Patched, Serial
Serial.test  thrpt   10  1624.531 ± 15.792  ops/s  ; <---- matches G1 now, because young is not tiny

Before:

$ build/linux-x86_64-zero-release/jdk/bin/java -Xlog:gc -Xlog:gc+init Alloc.java
[0.003s][info][gc     ] Using G1
...
[0.005s][info][gc,init] Memory: 125G
...
[0.005s][info][gc,init] Heap Region Size: 1M
[0.005s][info][gc,init] Heap Min Capacity: 8M
[0.005s][info][gc,init] Heap Initial Capacity: 16M
[0.005s][info][gc,init] Heap Max Capacity: 256M

After:

$ build/linux-x86_64-zero-release/jdk/bin/java -Xlog:gc -Xlog:gc+init Alloc.java
[0.003s][info][gc     ] Using G1
...
[0.007s][info][gc,init] Memory: 125G
...
[0.007s][info][gc,init] Heap Region Size: 16M
[0.007s][info][gc,init] Heap Min Capacity: 16M
[0.007s][info][gc,init] Heap Initial Capacity: 2016M
[0.007s][info][gc,init] Heap Max Capacity: 30208M

---

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Issue

• JDK-8294751: Zero: Allow larger default heaps

Reviewers

• Ioi Lam (@iklam - Reviewer)
• Roman Kennke (@rkennke - Reviewer)

Reviewing

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[mlbridge]

Webrevs

• 01: Full - Incremental (9d120795)
• 00: Full (d3d831e0)

[iklam]

Do we need to overhaul the other combinations as well? I don't see why we have to artificially limit the heap sizes. Here's the pd value for MaxRAM, which is defined identically for all platforms:

• no C2 = 1GB
• C2 on 32-bit = 4GB
• C2 on 64-bit = 128 GB

Also, if you want to do it for only ZERO for now, I think it's better to set the value inside compiler_globals_pd.hpp

#ifdef ZERO
define_pd_global(uint64_t,MaxRAM,                    128ULL*G);
#else 
define_pd_global(uint64_t,MaxRAM,                    1ULL*G);
#endif

[shipilev]

Do we need to overhaul the other combinations as well? I don't see why we have to artificially limit the heap sizes.

Probably. But as always with ergonomics, it might have unintended consequences.

Also, if you want to do it for only ZERO for now, I think it's better to set the value inside compiler_globals_pd.hpp

Yeah, @tstuefe asked about this in the previous PR too. Let's move both flags to that .hpp then. See new commit.

[openjdk]

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

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

8294751: Zero: Allow larger default heaps

Reviewed-by: iklam, rkennke

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At the time when this comment was updated there had been 48 new commits pushed to the master branch:

• 33d0618: 6616245: NullPointerException when using JFileChooser with a custom FileView
• fba763f: 8291519: jdk/jfr/api/event/TestShouldCommit.java failed with Unexpected value of shouldCommit()
• 6053bf0: 8293782: Shenandoah: some tests failed on lock rank check
• 4435d56: 8282395: URL.openConnection can throw IOOBE
• fe70487: 8294958: java/net/httpclient/ConnectTimeout tests are slow
• 97f1321: 8294356: IGV: scheduled graphs contain duplicated elements
• 5e05e42: 8294901: remove pre-VS2017 checks in Windows related coding
• e775acf: 8293986: Incorrect double-checked locking in com.sun.beans.introspect.ClassInfo
• 9d116ec: 8294262: AArch64: compiler/vectorapi/TestReverseByteTransforms.java test failed on SVE machine
• 4b17d28: 8294261: AArch64: Use pReg instead of pRegGov when possible
• ... and 38 more: https://git.openjdk.org/jdk/compare/2ceebf681ffd6f9bf6967fd81b30d721bc010b94...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.

[shipilev]

GHA re-run returned green. Yet, this PR checks report some failures. This is an infrastructure hiccup.

@tstuefe, the move of these checks to header definitions -- that is what you wanted to see, right?

[rkennke]

Seems reasonable and patch looks good!

Thanks,
Roman

[shipilev]

Thanks!

/integrate

[openjdk]

Going to push as commit 3ebe5ad.
Since your change was applied there have been 48 commits pushed to the master branch:

• 33d0618: 6616245: NullPointerException when using JFileChooser with a custom FileView
• fba763f: 8291519: jdk/jfr/api/event/TestShouldCommit.java failed with Unexpected value of shouldCommit()
• 6053bf0: 8293782: Shenandoah: some tests failed on lock rank check
• 4435d56: 8282395: URL.openConnection can throw IOOBE
• fe70487: 8294958: java/net/httpclient/ConnectTimeout tests are slow
• 97f1321: 8294356: IGV: scheduled graphs contain duplicated elements
• 5e05e42: 8294901: remove pre-VS2017 checks in Windows related coding
• e775acf: 8293986: Incorrect double-checked locking in com.sun.beans.introspect.ClassInfo
• 9d116ec: 8294262: AArch64: compiler/vectorapi/TestReverseByteTransforms.java test failed on SVE machine
• 4b17d28: 8294261: AArch64: Use pReg instead of pRegGov when possible
• ... and 38 more: https://git.openjdk.org/jdk/compare/2ceebf681ffd6f9bf6967fd81b30d721bc010b94...master

Your commit was automatically rebased without conflicts.

[openjdk]

@shipilev Pushed as commit 3ebe5ad.

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