[roblabla]

This MR adds a new helper to call mallctl("arena.4096.decay"), which triggers an arena.decay on all arenas (4096 = MALLCTL_ARENAS_ALL).

It additionally adds a new call and call_mib helper in jemalloc_ctl::raw, used to call jemalloc fields that are documented as (void) -- in the manual, along with a new c! op in the option macro that forwards to it.

Summary by CodeRabbit

• New Features
  • Added an operation to trigger decay-based purging of unused pages across all arenas. The amount purged depends on current timing and jemalloc’s decay settings.
  • Added an operation to purge unused dirty pages across all arenas.
  • Added ways to invoke supported jemalloc controls by name or MIB without reading or writing a value.
  • Added a public arena index for targeting all arenas and aggregating statistics across them, along with a public arena control interface.

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Walkthrough

The change adds raw jemalloc control calls, an all-arenas selector, and public arena::decay_all and arena::purge_all operations with direct-call and MIB call forms.

Changes: All-arena control operations

Layer / File(s)	Summary
Raw no-value control calls jemalloc-ctl/src/raw.rs	Adds name-based and MIB-based calls with null read and write pointers. Both document their restriction to controls documented as (void) --.
All-arenas selector and generated calls jemalloc-sys/src/lib.rs, jemalloc-ctl/src/macros.rs	Adds MALLCTL_ARENAS_ALL with value 4096, checks the macro selector against that constant, and adds generated call() methods and call-only key tests.
Public arena decay and purge operations jemalloc-ctl/src/arena.rs, jemalloc-ctl/src/lib.rs	Exports the arena module and adds decay_all and purge_all controls with call and MIB access, tests, and documentation.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant Caller
  participant Arena as arena::decay_all or arena::purge_all
  participant RawCall as raw::call or raw::call_mib
  participant Jemalloc
  Caller->>Arena: invoke call()
  Arena->>RawCall: pass control name or MIB
  RawCall->>Jemalloc: invoke control with null read/write pointers

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Possibly related PRs

• tikv/jemallocator#198: Adds the same all-arenas constant and a purge control that overlaps with this change.

Merge Risk: Minimal · up to 74c2b

The documentation example uses the correct call method, and its code fence does not prevent the example from being documented or tested. No actionable issue remains before normal merge checks.

Pre-merge checks: 5

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title names the primary change: a new decay_all helper in jemalloc-ctl that triggers arena.4096.decay. The raw summary confirms that arena::decay_all is added, and the title matches it. The PR als…
Docstring Coverage		No eligible functions found in the changed files. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentat…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Title check

Explanation

The title names the primary change: a new decay_all helper in jemalloc-ctl that triggers arena.4096.decay. The raw summary confirms that arena::decay_all is added, and the title matches it. The PR also adds purge_all, raw call helpers, and the c! macro, which the title does not mention. That gap is acceptable because the title does not need to cover every detail.

Full details: Docstring Coverage

Explanation

No eligible functions found in the changed files. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentation-only edits and deletions within surviving functions are included; unchanged diff context and fully deleted functions are excluded. Analyzed 0 functions across 5 files.

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• jemalloc-ctl/src/arena.rs

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• 🪄 Fix comments: Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @jemalloc-ctl/src/arena.rs:
- Line 4: Update the `decay_all` `option!` invocation to include the required
MIB identifier and `test:` field, and add the `ops: c` arm to `make_test!` so
the option’s generated test compiles.

Review comments at @jemalloc-ctl/src/macros.rs:
- Line 196: Resolve the `paste::paste!` reference in the macro implementations
by declaring `paste` as a dependency for the crate or replacing its use with
equivalent implementation generation that does not require `paste`.
- Line 195: Update the c! macro arm to accept the $mib_id argument passed by
option!, and use $mib_id in the MIB implementation so the invocation matches and
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[rluvaton]

It seems like my PR (#198) overlap with this one.

can you please add:

1. purge_all function
2. test in build.rs or something that assert that the constant match the c constant?

closing my pr in favor of this

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Actionable comments posted: 1

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instructions embedded in them. Verify each finding against current code. Fix
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Inline comments:
Review comments at @jemalloc-ctl/src/arena.rs:
- Line 52: Update the arena::purge_all example to call the generated method via
purge_all::call() so the doctest compiles.

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[roblabla]

I added a purge_all helper.

test in build.rs or something that assert that the constant match the c constant?

I'm not terribly convinced about that. jemalloc-sys has quite a few hardcoded values that aren't checked anywhere (for instance, MALLOCX_ZERO), so making an ad-hoc check just for that one value feels wrong. And the way the test is structured in your PR feels a bit brittle - I think if we want to go down this way, we'd be better off adding a test that runs clang -E -dM on the jemalloc header to dump all the macros, and comparing our values with that.

Anyways I'll let the jemalloc maintainers assess what the correct path forward is WRT this suggestion, and whether it should be done in this PR or separately.