experiment: 6.18 + HZ=1000 + voluntary preemption (ABX-498 A/B) - #15
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AprilNEA wants to merge 3 commits into
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experiment: 6.18 + HZ=1000 + voluntary preemption (ABX-498 A/B)#15AprilNEA wants to merge 3 commits into
AprilNEA wants to merge 3 commits into
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Container start is a chain of jiffy-rounded scheduler waits across the containerd/shim/runc/dockerd IPC handshake; at HZ=100 each rounds up to 10 ms. Cross-engine bench (ABX-496) measured container churn ~5x slower than a matched Colima guest (HZ=1000), which dominates multi-step docker builds (each step is a container): simple cold 8.1s vs 0.6s, 12-stage 12.7s vs 1.5s. NO_HZ_IDLE keeps the tick off when idle, so the idle-CPU target is unaffected — the cost is purely more timer interrupts under active load, the right trade for a build/dev runtime chasing OrbStack parity.
The HZ bump is a choice symbol; olddefconfig silently drops or rewrites unsatisfiable choices, so guard it the same way the script already guards the squashfs/netfilter symbols.
Experiment for arcbox ABX-498: lazy preemption (PREEMPT_BUILD + PREEMPT_RCU) measures 2.3x slower same-core context switch (8.6 vs 3.7 us pipe ping-pong) and regresses veth del from ~0 ms to 74 ms (rcu_barrier) vs the 6.12 voluntary build. Keeps HZ=1000.
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CI-build-only experiment for arcbox ABX-498 — do not merge as-is. Reverts the lazy-preemption switch on top of the HZ=1000 branch to isolate the preemption model's cost: lazy/PREEMPT_RCU measures 2.3× slower same-core context switch and 74 ms veth del (rcu_barrier) vs 6.12-voluntary. If this build restores ~3.7 µs / ~0 ms on the same 6.18 base, the fix direction is voluntary (or PREEMPT_DYNAMIC defaulting to voluntary) + HZ=1000.