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rts: halve max heap, return memory to OS after parsing spikes #59

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rts: halve max heap, return memory to OS after parsing spikes #59

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17 changes: 14 additions & 3 deletions docker/rts-flags.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -36,11 +36,22 @@ NURSERY_MB=$((CORES * 16))
CHUNK_MB=$((NURSERY_MB / 32))
[ $CHUNK_MB -lt 8 ] && CHUNK_MB=8

# Max heap: 75% of RAM, minimum 2G
MAX_MB=$((RAM_MB * 3 / 4))
# Max heap: 50% of RAM, minimum 2G.
# The remaining half is left to: kernel + page cache, MUMPS Fortran solver
# (which allocates outside the GHC heap), parser intermediates that
# transiently inflate RSS above heap size, and the OOM headroom needed to
# let `-M` trigger a clean Haskell heap-exhaustion exit before the kernel
# OOM-killer fires.
MAX_MB=$((RAM_MB / 2))
[ $MAX_MB -lt 2048 ] && MAX_MB=2048

RTS_FLAGS="+RTS -N -M${MAX_MB}M -H${HEAP_MB}M -A${NURSERY_MB}M -n${CHUNK_MB}m -qg0 -c -F1.5 -I30 -RTS"
# -Fd1.0 (GHC 9.10+): return free heap blocks to the OS over ~1 idle period
# instead of holding them indefinitely after a parsing spike. Default decay
# (4.0) keeps RSS pinned near the peak for minutes.
# -I0.3 (GHC default): trigger idle-time major GC promptly. The previous
# -I30 deferred GC for 30 s, hiding live-data drops and starving -Fd of
# free blocks to release.
RTS_FLAGS="+RTS -N -M${MAX_MB}M -H${HEAP_MB}M -A${NURSERY_MB}M -n${CHUNK_MB}m -qg0 -c -F1.5 -Fd1.0 -I0.3 -RTS"

echo "RTS_FLAGS=\"$RTS_FLAGS\""

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