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zakkak/bmark-setup.sh

Created April 29, 2026 12:34
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A script to setup an AMD 7950X linux machine to "benchmark" mode
Raw
bmark-setup.sh
#!/usr/bin/env bash
# TUNED FOR AMD 7950X
# set -x
usage() {
echo "Usage: $(basename "$0") {start|stop|drop-caches}"
exit 1
}
case "${1}" in
start)
# Switch to performance governor so the CPU runs at max non-boost frequency
cpupower frequency-set -g performance
# Disable turbo boost — boost clocks vary with thermals, power budget,
# and active core count, which hurts reproducibility
echo 0 > /sys/devices/system/cpu/cpufreq/boost
# Pin all cores to the nominal 4.5 GHz (Ryzen 9 7950X base clock);
# setting min and max separately works around amd-pstate-epp rejecting
# simultaneous -d/-u when the new range conflicts with the current one
cpupower frequency-set --min 4.5GHz
cpupower frequency-set --max 4.5GHz
# With amd-pstate-epp + performance governor, EPP is automatically
# locked to "performance" — no manual write needed
# Disable deep C-states (C2, C3) to reduce wakeup latency; keep POLL and C1
echo 1 | tee /sys/devices/system/cpu/cpu*/cpuidle/state2/disable > /dev/null
echo 1 | tee /sys/devices/system/cpu/cpu*/cpuidle/state3/disable > /dev/null
# Reduce dirty page writeback thresholds for lower I/O latency
sysctl -q vm.dirty_ratio=10 vm.dirty_background_ratio=3
# Lower swappiness to discourage swapping out process memory
sysctl -q vm.swappiness=10
# Allow unprivileged access to perf events (1 = kernel+user, no raw tracepoints)
echo 1 > /proc/sys/kernel/perf_event_paranoid
# Expose kernel symbol addresses in /proc/kallsyms to all users
echo 0 > /proc/sys/kernel/kptr_restrict
# Disable Address Space Layout Randomization (ASLR) for reproducible addresses
echo 0 > /proc/sys/kernel/randomize_va_space
# Disable scheduler autogroup so all benchmark threads compete fairly
# in the global CFS run queue instead of per-TTY groups
sysctl -q kernel.sched_autogroup_enabled=0
# Disable Transparent Huge Pages — khugepaged compaction and defrag
# cause unpredictable latency spikes during allocation
echo never > /sys/kernel/mm/transparent_hugepage/enabled
echo never > /sys/kernel/mm/transparent_hugepage/defrag
# Stop irqbalance to prevent IRQ migration between CPUs mid-run
systemctl stop irqbalance 2>/dev/null || true
# Disable NMI watchdog — its periodic interrupts add measurement noise
sysctl -q kernel.nmi_watchdog=0
# Disable NUMA balancing — the 7950X has 2 CCDs (often NUMA nodes);
# automatic page migration between them adds variance
sysctl -q kernel.numa_balancing=0
# Disable timer migration to prevent timers from moving to busy CPUs
# and causing unexpected wakeups
sysctl -q kernel.timer_migration=0
# Disable SMT (hyperthreading) to eliminate sibling-thread interference;
# halves thread count but greatly reduces core-level contention jitter
echo off > /sys/devices/system/cpu/smt/control
# Disable Kernel Samepage Merging — its background scanning adds CPU noise
echo 0 > /sys/kernel/mm/ksm/run
# Print current CPU frequencies to confirm the governor change took effect
grep -E '^cpu MHz' /proc/cpuinfo
echo "ready to start!"
;;
stop)
# Re-enable SMT (hyperthreading) first so all CPUs are online
# before setting frequency/governor on them
echo on > /sys/devices/system/cpu/smt/control
# Re-enable turbo boost
echo 1 > /sys/devices/system/cpu/cpufreq/boost
# Restore powersave governor (the amd-pstate-epp default); this
# lets the firmware manage frequency and unlocks EPP writes
cpupower frequency-set -g powersave
# Restore the full hardware frequency range (set separately for amd-pstate-epp)
cpupower frequency-set --min 425MHz
cpupower frequency-set --max 5883MHz
# Restore energy performance preference to balance_performance
# (writable now that governor is powersave)
echo balance_performance | tee /sys/devices/system/cpu/cpu*/cpufreq/energy_performance_preference > /dev/null
# Re-enable deep C-states (C2, C3)
echo 0 | tee /sys/devices/system/cpu/cpu*/cpuidle/state2/disable > /dev/null
echo 0 | tee /sys/devices/system/cpu/cpu*/cpuidle/state3/disable > /dev/null
# Restore default dirty page writeback thresholds and swappiness
sysctl -q vm.dirty_ratio=20 vm.dirty_background_ratio=10 vm.swappiness=60
# Re-enable scheduler autogroup (desktop behavior)
sysctl -q kernel.sched_autogroup_enabled=1
# Re-enable ASLR (2 = full randomization)
echo 2 > /proc/sys/kernel/randomize_va_space
# Re-enable Transparent Huge Pages
echo always > /sys/kernel/mm/transparent_hugepage/enabled
echo always > /sys/kernel/mm/transparent_hugepage/defrag
# Restart irqbalance for normal IRQ distribution
systemctl start irqbalance 2>/dev/null || true
# Re-enable NMI watchdog
sysctl -q kernel.nmi_watchdog=1
# Re-enable NUMA balancing
sysctl -q kernel.numa_balancing=1
# Re-enable timer migration
sysctl -q kernel.timer_migration=1
# Re-enable Kernel Samepage Merging
echo 1 > /sys/kernel/mm/ksm/run
# Print current CPU frequencies to confirm the governor reverted
grep -E '^cpu MHz' /proc/cpuinfo
;;
drop-caches)
# Safely drop caches without breaking zram swap
# This is a workaround for kernel 6.19.9 + zram-generator issue where
# drop_caches can leave zram in a "busy" state that prevents suspend
echo "Disabling swap..."
swapoff -a
echo "Dropping caches (page cache, dentries, and inodes)..."
sync
echo 3 > /proc/sys/vm/drop_caches
echo "Re-enabling swap..."
swapon -a
echo "Caches dropped successfully!"
;;
*)
usage
;;
esac
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