A/B on identical 2-node beam-heavy runs (scratchpad/night14/segperf.sh),
BT_BEAM_SEGFRESH=1 (swept behaviour) vs =0 (pre-sweep compose at the beam
site, the only per-frame swept call):
fresh(swept) legacy(pre-sweep)
rstat blocks>50ms 0 0
maxDraw worst 730ms 646ms (mission-load spike, BOTH)
segperf dirty-passes 38/s 4/s <- the sweep DOES multiply
segperf accessor ms 0.97/s 0.57/s <- ...by 0.4 ms/s. Noise.
So the invalidation-storm hypothesis I filed on #149 is wrong by three orders
of magnitude, and Oracle's sustained 50-104ms stall window does NOT reproduce
on this rig at all. Refusing to guess a third time: the build now carries the
telemetry to answer it on the machine that actually regresses --
[segperf] calls= dirty= ms= printed beside every [rstat] window under
BT_PERF_LOG (JMOVER counters; two integer increments when unset), and
BT_BEAM_SEGFRESH=0 remains as a one-env A/B for the beam site.
Default stays FRESH (the swept accessor): its measured cost is trivial and it
is the correctness-cautious side while the peer-beam-staleness question is
unmeasured.
Next for #149: Oracle runs one session with BT_PERF_LOG=1. If [segperf] ms is
large inside his stalled windows, segment work is implicated on HIS
configuration and BT_BEAM_SEGFRESH=0 gives the immediate A/B; if it is small
(as here), the stall is elsewhere in the 817->857 delta and we hunt with his
numbers instead of my theories.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018SgmXGNMXavXiafKXf9MDC
