The latency_harness.py harness spawns the bench binary on a PTY,
records monotonic_ns() per stdout line, and reports inter-arrival
gap distribution (median / p99 / p99.9 / max). Tail latency is
Decision 10's central real-time claim; total wall-time and RSS are
the wrong metrics for that question.
Paired fixtures: bench_latency_implicit (Boehm-fair, no mode
annotations, leaks under --alloc=rc) and bench_latency_explicit
(mode-annotated hot path, what RC was built for). Both use a
depth-19 balanced tree (~16 MB) as the persistent live working
set, plus per-op IntList build+sum churn forcing GC pressure
under Boehm.
Authored by ailang-bencher; ships evidence, not features.
Adds rc to the modes list and an rc/bump ratio column in the
results table. The rc/bump ratio is the decisive number for
Decision 10's Boehm-retirement threshold (target 1.3x).
Adds --alloc=<gc|bump> to ail build/run. Bump path links a 256MB
no-free arena C stub instead of libgc; IR is byte-identical except
for the @GC_malloc → @bump_malloc symbol swap. Bench harness times
two allocation-heavy workloads (list cons/sum and balanced tree
build/walk) under both modes.
Numbers (RUNS=5, median of 4):
bench_list_sum gc 0.141s bump 0.048s +194%
bench_tree_walk gc 0.103s bump 0.041s +151%
Bucket: large. ~60% of runtime is Boehm on these workloads —
upper bound for any realistic program. Both fixtures hold the
heap fully live, so the cost we're seeing is Boehm's allocate
path itself, not collection work; that fact narrows the design
space for the GC discussion.
- crates/ailang-codegen: AllocStrategy enum, three callsites and
the IR header parameterised.
- crates/ail/src/main.rs: --alloc flag plumbed; bump runtime
located + compiled on demand.
- runtime/bump.c: 256MB static arena, abort-on-overflow.
- examples/bench_list_sum, bench_tree_walk: accumulator-form
fixtures (textbook recursive sum was constructor-blocked).
- bench/run.sh: harness with Python timing helper (Arch's
/usr/bin/time isn't part of the base install).
No language-level changes; default --alloc=gc, all 141 workspace
tests green, all 5 IR snapshots unchanged, 11 prior fixtures
produce identical stdout.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Brummel