Honor -Xmx under the java-web command - #13

The PR adds support for the -Xmx flag to cap the maximum array size and Runtime.maxMemory() value, fixing a timeout in OpenJDK test Test8027905. A new test verifies that a 32 MB array fails and a 4 MB array succeeds under -Xmx16m, matching HotSpot behavior. The implementation parses the size suffix (k/m/g), caps at 1 GB, and updates documentation.

_{review-bot, model nvidia/nemotron-3-ultra-550b-a55b:free, verdict approve}

This PR adds support for the -Xmx flag to cap the maximum heap size, which limits individual array allocations and sets the value reported by Runtime.maxMemory(). The implementation parses -Xmx with k/m/g suffixes (or bare bytes), validates a 2 MB minimum matching x64 HotSpot, rounds up to 2 MB steps, and caps at 1 GB. A new test verifies the behavior against HotSpot: a 32 MB array fails, a 4 MB array succeeds, and -Xmx17m reports 18874368 bytes.

Not approved: 2 earlier points are still open in the threads.

_{review-bot, model nvidia/nemotron-3-ultra-550b-a55b:free, verdict comment}

All points from the last review are settled in the threads.

_{review-bot, model nvidia/nemotron-3-ultra-550b-a55b:free, verdict approve}

The PR adds -Xmx support to the java-web command, allowing the maximum heap size to be set (capped at 1 GB, rounded up to 2 MB steps, minimum 2 MB). The implementation parses the flag in src/node.ts, validates and rounds the value, then calls setMaxHeap in src/runtime.ts which updates the mutable MAX_HEAP used for array allocation limits and Runtime.maxMemory(). A new test verifies the behavior matches x64 HotSpot for -Xmx17m (18874368 bytes). The previously discussed minimum-heap validation is now present in the code.

_{review-bot, model nvidia/nemotron-3-ultra-550b-a55b:free, verdict approve}

Actionable comments posted: 3

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Inline comments:
Review comments at @src/node.ts:
- Line 339: Update the argument handling around the `-Xmx` branch to detect any
`-Xmx` prefix before the generic `-X` handling. Accept valid heap-size arguments
as before, and reject malformed sizes such as `-Xmx16mb` instead of silently
ignoring them and falling back to the 1 GiB default.

Review comments at @src/runtime.ts:
- Line 366: Update the Runtime memory reporting used by totalMemory() and
freeMemory() so both values stay consistent with the configured maximum returned
by maxMemory(); preserve the relationship needed for maxMemory() - totalMemory()
+ freeMemory() to remain nonnegative when the maximum is small.
- Line 366: Update both heap and pool usage paths in the management MXBean code
that construct MemoryUsage, using MAX_HEAP as the limit. Ensure each returned
usage has consistent committed and maximum values so committed never exceeds
maximum, while preserving the existing usage semantics where possible.

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Reviewing files that changed from the base of the PR and between 91331e6 and 4902596.

Files selected for processing: 5

• docs/node.md
• src/node.ts
• src/runtime.ts
• test/heap/Heap.java
• test/programs.test.ts

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Additional context used

Learnings: 1

Learning: 2026-11-01T20:52:55.551Z

Learnt from: CR
Repo: Project516/java-web PR: 0
File: AGENTS.md:0-0
Timestamp: 2026-11-01T20:52:55.551Z
Learning: Source excerpt:
# java-web

## Direction

- Prove it with tests: programs whose output must match HotSpot exactly, and
  OpenJDK's own regression tests where they can run.

Applied to files:

• test/programs.test.ts

Additional comments: 3

docs/node.md: 1

22-22: LGTM!

test/heap/Heap.java: 1

1-16: LGTM!

test/programs.test.ts: 1

67-77: LGTM!

The PR adds support for the -Xmx flag to cap the maximum heap size (and thus the largest array allocation) at up to 1 GB, rounded up to 2 MB steps with a 2 MB minimum, matching x64 HotSpot behavior. The change threads the value through MAX_HEAP in runtime.ts, updates Runtime.maxMemory(), freeMemory(), totalMemory(), and the memory MXBean to respect the cap, and adds a test that verifies the rounding and allocation behavior against HotSpot.

_{review-bot, model nvidia/nemotron-3-ultra-550b-a55b:free, verdict approve}