slv-smt-disable

name	slv-smt-disable
description	Disable SMT (Hyper-Threading) by adding `nosmt=force` to GRUB. Required for stable single-thread performance on Solana validators / RPCs. Reboot required.

SLV SMT (Hyper-Threading) Disable Skill

Solana validator / RPC throughput is dominated by single-thread instruction performance, so disabling SMT consistently produces higher and more stable performance. Applied during slv v init / slv r init as part of the tuning phase.

How it works

Adds nosmt=force to GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub and runs update-grub. After reboot, the kernel only schedules on one logical thread per physical core.

Related ansible playbook

• ansible/cmn/smt_disable.yml — appends nosmt=force to GRUB and runs update-grub
• Idempotency marker: /var/lib/slv/.smt_disabled

Standalone run

ansible-playbook -i inventory.yml cmn/smt_disable.yml --limit <host>

Sets need_reboot=true only when GRUB actually changed; the orchestrator reboots when needed.

Verification

# on the host
cat /proc/cmdline                      # should contain nosmt=force
lscpu | grep -E 'Thread|Core|Socket'   # Thread(s) per core: 1

Rollback

sudo sed -i 's/ nosmt=force//' /etc/default/grub
sudo update-grub
sudo rm /var/lib/slv/.smt_disabled
sudo reboot