perf(config): HZ 100→1000 to cut container-start latency (ABX-496)

configs/arcbox-arm64.config

@@ -73,8 +73,16 @@ CONFIG_NR_CPUS=256
 # first byte). Also forward-compatible — 7.0 removes voluntary for
 # lazy-capable arches, and arm64/x86 both select ARCH_HAS_PREEMPT_LAZY.
 CONFIG_PREEMPT_LAZY=y
-CONFIG_HZ_100=y
-CONFIG_HZ=100
+# HZ=1000 (1 ms tick) not 100 (10 ms): container start is a chain of
+# jiffy-rounded scheduler waits (containerd poll, shim handshake
+# completions, runc, dockerd↔containerd gRPC backoff). At HZ=100 each
+# rounds up to 10 ms, making container churn ~5x slower than Colima's
+# HZ=1000 guest — the dominant cost in multi-step `docker build` (each
+# step is a container). NO_HZ_IDLE keeps the idle-CPU target intact
+# (tickless when idle), so this is latency-only cost under active load.
+# See ABX-496.
+CONFIG_HZ_1000=y
+CONFIG_HZ=1000
 
 # Virtualization guest support
 CONFIG_PARAVIRT=y

configs/arcbox-x86_64.config

@@ -72,8 +72,16 @@ CONFIG_NR_CPUS=256
 # first byte). Also forward-compatible — 7.0 removes voluntary for
 # lazy-capable arches, and arm64/x86 both select ARCH_HAS_PREEMPT_LAZY.
 CONFIG_PREEMPT_LAZY=y
-CONFIG_HZ_100=y
-CONFIG_HZ=100
+# HZ=1000 (1 ms tick) not 100 (10 ms): container start is a chain of
+# jiffy-rounded scheduler waits (containerd poll, shim handshake
+# completions, runc, dockerd↔containerd gRPC backoff). At HZ=100 each
+# rounds up to 10 ms, making container churn ~5x slower than Colima's
+# HZ=1000 guest — the dominant cost in multi-step `docker build` (each
+# step is a container). NO_HZ_IDLE keeps the idle-CPU target intact
+# (tickless when idle), so this is latency-only cost under active load.
+# See ABX-496.
+CONFIG_HZ_1000=y
+CONFIG_HZ=1000
 
 # Virtualization guest support
 CONFIG_HYPERVISOR_GUEST=y

scripts/build-kernel.sh

@@ -73,7 +73,7 @@ do_build() {
     # dependency gate in the fragment otherwise degrades silently — 6.18 did
     # exactly that to the legacy iptables stack via NETFILTER_XTABLES_LEGACY).
     for sym in CONFIG_SQUASHFS_DECOMP_MULTI_PERCPU CONFIG_IP_NF_NAT \
-               CONFIG_IP6_NF_NAT; do
+               CONFIG_IP6_NF_NAT CONFIG_HZ_1000; do
         grep -q "^$sym=y" .config || {
             echo "ERROR: $sym missing after olddefconfig" >&2
             exit 1
@@ -132,7 +132,7 @@ cd linux-$KERNEL_VERSION
 sh /workspace/scripts/inject-drivers.sh /workspace
 cp /workspace/configs/arcbox-$TARGET_ARCH.config .config
 make ARCH=$TARGET_ARCH olddefconfig
-for sym in CONFIG_SQUASHFS_DECOMP_MULTI_PERCPU CONFIG_IP_NF_NAT CONFIG_IP6_NF_NAT; do
+for sym in CONFIG_SQUASHFS_DECOMP_MULTI_PERCPU CONFIG_IP_NF_NAT CONFIG_IP6_NF_NAT CONFIG_HZ_1000; do
     grep -q \"^\$sym=y\" .config || {
         echo \"ERROR: \$sym missing after olddefconfig\" >&2
         exit 1