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fix(gc): route the census thread-locals through hot TLS #9781

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fix(gc): route the census thread-locals through hot TLS #9781

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c0e2f7a
fix(gc): route the census thread-locals through hot TLS
Sep 5, 2026
4367aad
docs(changelog): add PR 9781 fragment
Sep 5, 2026
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10 changes: 10 additions & 0 deletions changelog.d/9781-census-hot-tls.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
**The GC census thread-locals no longer pay `_tlv_get_addr`.** `gc::census`
is compiled unconditionally, so its two ungated `thread_local!` blocks were
in shipping builds and cost an out-of-line libdyld call per access on Darwin
— including the `ARMED` flag that gates whether the census does anything at
all. Both now use `crate::perry_thread_local!`, the same treatment the four
other recent declarations received; every call site already went through
`.with()`, so nothing else changed.

This also restores the `self-test-checkers` job, whose thread-local policy
ratchet (#7469) had been failing on main and on every open PR.
4 changes: 2 additions & 2 deletions crates/perry-runtime/src/gc/census.rs
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Expand Up @@ -43,7 +43,7 @@ static SIGNAL_PENDING: AtomicBool = AtomicBool::new(false);
static SIGNAL_INSTALLED: AtomicBool = AtomicBool::new(false);
static MAIN_THREAD: OnceLock<std::thread::ThreadId> = OnceLock::new();

thread_local! {
crate::perry_thread_local! {
static ARMED: Cell<bool> = const { Cell::new(false) };
static SEQ: Cell<u32> = const { Cell::new(0) };
static LABEL: RefCell<&'static str> = const { RefCell::new("manual") };
Expand Down Expand Up @@ -177,7 +177,7 @@ fn census_service_signal() {
super::js_gc_collect();
}

thread_local! {
crate::perry_thread_local! {
/// Pass-1 snapshot: sorted header addresses that were marked when mark
/// propagation finished (see the module docs).
static PASS1_MARKED: RefCell<Option<Vec<usize>>> = const { RefCell::new(None) };
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