An internal report from cross-engine write-path instrumentation: with
individual writes slower than the idle window (a contended disk), every
inter-write gap looked idle and fired a background full flush — 15 extra
flushes during 100 contended adds, amplifying the very pressure that
slowed the writes. The law now: an idle fire landing within the spacing
floor of the last flush DEFERS to the floor boundary instead of flushing;
the floor is min(interval, 10× the CONFIGURED idle window) — scaled to
caller intent (a tiny idle window keeps fast idle-driven durability;
default 2s/30s config gets a 20s floor), derived from the configured
idle, never from a deferred re-arm delay (which would compound into
runaway deferral). Deferred is never dropped: a lone write on a
then-quiet store still persists at the floor without any further write
arriving.
Pins: the contended-shape pin (six slow-spaced writes fire ≤2 idle
flushes, not one per gap; then still persist) + the original quiet-store
idle pin unchanged. Unit 2055/2055.
David Snelling
a50726e6a8