Escalado de frecuencia de CPU y gestión de energía
Los procesadores modernos soportan escalado dinámico de frecuencia y voltaje (DVFS) permitiendo operación eficiente energéticamente mientras se mantiene el rendimiento cuando es necesario. La gestión estratégica de frecuencia de CPU equilibra consumo de energía, consideraciones térmicas y requisitos de latencia. Esta guía cubre gobernadores de escalado de frecuencia de CPU, gestión de turbo boost y estrategias de despliegue consciente de la energía.
Tabla de contenidos
- Fundamentos de frecuencia de CPU
- Gobernadores de escalado de frecuencia
- Controlador intel_pstate
- Escalado ACPI de AMD Ryzen
- Gestión de Turbo Boost
- Estados de CPU (P-states y C-states)
- Estrategias de gestión de energía
- Monitoreo de frecuencias de CPU
- Conclusión
Fundamentos de frecuencia de CPU
Entender escalado de CPU
# Check current CPU frequency
cat /proc/cpuinfo | grep "cpu MHz"
# Maximum and minimum frequency per CPU
watch -n 1 'cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq'
watch -n 1 'cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_min_freq'
# Current scaling frequency
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq
# Available frequency steps
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
Compensación entre potencia y rendimiento
# At lower frequencies:
# - Reduced power consumption (quadratic with voltage)
# - Lower heat output
# - Increased latency
# - Reduced throughput
# At higher frequencies:
# - Maximum performance
# - Higher power consumption
# - Increased thermal output
# - Lower latency
# Typical energy savings:
# - 50% frequency reduction = 60-70% power reduction
# - But performance reduced proportionally or more
Gobernadores de escalado de frecuencia
Gobernadores disponibles
# List available governors
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors
# Output typical:
# powersave performance schedutil ondemand conservative
# Current governor
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
# Governor characteristics:
# - powersave: Minimize frequency, minimize power
# - performance: Maximum frequency always
# - ondemand: Scale based on CPU load dynamically
# - conservative: Gradual frequency changes
# - schedutil: Kernel scheduler driven (modern, default)
Selección de gobernadores
# Set performance governor (latency-sensitive applications)
for cpu in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor; do
echo "performance" | sudo tee $cpu
done
# Set powersave governor (power-optimized workloads)
for cpu in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor; do
echo "powersave" | sudo tee $cpu
done
# Set ondemand governor (balanced approach)
for cpu in /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor; do
echo "ondemand" | sudo tee $cpu
done
# Verify change
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
Sintonización del gobernador ondemand
# ondemand parameters
ls /sys/devices/system/cpu/cpufreq/ondemand/
# Sampling rate (default 10000 = 10ms)
cat /sys/devices/system/cpu/cpufreq/ondemand/sampling_rate
echo 5000 | sudo tee /sys/devices/system/cpu/cpufreq/ondemand/sampling_rate
# Up threshold (default 80%)
# Frequency increases when CPU load exceeds this
cat /sys/devices/system/cpu/cpufreq/ondemand/up_threshold
echo 60 | sudo tee /sys/devices/system/cpu/cpufreq/ondemand/up_threshold
# Powersave bias (0=performance, 1000=powersave)
cat /sys/devices/system/cpu/cpufreq/ondemand/powersave_bias
echo 500 | sudo tee /sys/devices/system/cpu/cpufreq/ondemand/powersave_bias
Sintonización del gobernador conservative
# conservative parameters (gradual frequency changes)
ls /sys/devices/system/cpu/cpufreq/conservative/
# Frequency scaling down threshold
cat /sys/devices/system/cpu/cpufreq/conservative/down_threshold
echo 20 | sudo tee /sys/devices/system/cpu/cpufreq/conservative/down_threshold
# Frequency scaling step (default 5%)
cat /sys/devices/system/cpu/cpufreq/conservative/freq_step
echo 10 | sudo tee /sys/devices/system/cpu/cpufreq/conservative/freq_step
Controlador intel_pstate
Escalado de frecuencia de CPU Intel
# Check if intel_pstate is active
cat /sys/devices/system/cpu/cpu0/cpufreq/driver
# intel_pstate specific parameters
ls /sys/devices/system/cpu/intel_pstate/
# Min/max performance percentage
cat /sys/devices/system/cpu/intel_pstate/min_perf_pct
cat /sys/devices/system/cpu/intel_pstate/max_perf_pct
# Set maximum performance (all turbo capability)
echo 100 | sudo tee /sys/devices/system/cpu/intel_pstate/max_perf_pct
# Set minimum performance (power saving)
echo 50 | sudo tee /sys/devices/system/cpu/intel_pstate/min_perf_pct
# No turbo (disable turbo boost)
cat /sys/devices/system/cpu/intel_pstate/no_turbo
echo 1 | sudo tee /sys/devices/system/cpu/intel_pstate/no_turbo
# Energy Performance Preference (HWP - Hardware P-States)
# High performance: 0
# Balanced: 50
# Power saving: 100
if [ -f /sys/devices/system/cpu/cpu0/cpufreq/energy_performance_preference ]; then
echo "performance" | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/energy_performance_preference
fi
Escalado ACPI de AMD Ryzen
Configuración de frecuencia de CPU AMD
# Check AMD frequency scaling driver
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver
# AMD-specific governor
# Prefer 'amd_pstate' if available (newer)
# Falls back to 'acpi-cpufreq' on older systems
# AMD amd_pstate parameters
ls /sys/devices/system/cpu/cpufreq/amd-pstate*
# CPU governor selection
echo "schedutil" | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
Gestión de Turbo Boost
Intel Turbo Boost
# Check turbo boost status
cat /sys/devices/system/cpu/intel_pstate/no_turbo
# Output: 0 = enabled, 1 = disabled
# Disable turbo boost (power saving, consistent frequency)
echo 1 | sudo tee /sys/devices/system/cpu/intel_pstate/no_turbo
# Enable turbo boost (maximum performance)
echo 0 | sudo tee /sys/devices/system/cpu/intel_pstate/no_turbo
# Monitor turbo boost usage
watch -n 1 'cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq'
Control de boost AMD
# Check AMD boost status
cat /sys/devices/system/cpu/cpufreq/boost
# Disable boost (power and thermal management)
echo 0 | sudo tee /sys/devices/system/cpu/cpufreq/boost
# Enable boost (maximum performance)
echo 1 | sudo tee /sys/devices/system/cpu/cpufreq/boost
# Monitor boost state
watch -n 1 'cat /sys/devices/system/cpu/cpufreq/boost'
Estados de CPU (P-states y C-states)
P-states (Estados de rendimiento)
# List available P-states
cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
# P-states determine CPU frequency
# P0: Highest frequency (maximum performance)
# P1: Reduced frequency
# ...
# Pn: Minimum frequency (power saving)
# Lock to specific P-state
echo 2400000 | sudo tee /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed
# Return to automatic scaling
echo "powersave" | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
C-states (Estados de sueño)
# Check available C-states
cat /sys/devices/system/cpu/cpu0/cpuidle/states/*/name
# Typical C-states:
# C0: Running (P-state controls frequency)
# C1: Halt (minimal latency, minimal power saving)
# C2: Stop grant (deeper sleep)
# C3: Sleep (deepest, highest latency)
# Monitor C-state residency
watch -n 1 'cat /sys/devices/system/cpu/cpu0/cpuidle/*/time'
# Disable deeper C-states for latency-sensitive workloads
# Kernel parameter: processor.max_cstate=1
# Add to GRUB: GRUB_CMDLINE_LINUX="processor.max_cstate=1"
Estrategias de gestión de energía
Estrategia de carga de servidor
# Database server (predictable load, latency critical)
# Strategy: Performance mode, no turbo boost variability
echo "performance" | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
# Web server (variable load, throughput important)
# Strategy: schedutil governor, enable turbo boost
echo "schedutil" | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
echo 0 | sudo tee /sys/devices/system/cpu/intel_pstate/no_turbo
# Batch processing (throughput optimized)
# Strategy: Performance + turbo, disable C-states
echo "performance" | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
echo 0 | sudo tee /sys/devices/system/cpu/intel_pstate/no_turbo
# Power-optimized (max power saving)
echo "powersave" | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
echo 1 | sudo tee /sys/devices/system/cpu/intel_pstate/no_turbo
Configuración persistente
# Create frequency scaling service
cat > /etc/systemd/system/cpu-frequency.service <<'EOF'
[Unit]
Description=Set CPU Frequency Governor
After=sysfs.mount
DefaultDependencies=no
[Service]
Type=oneshot
ExecStart=/bin/bash -c 'echo schedutil | tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor'
RemainAfterExit=yes
[Install]
WantedBy=multi-user.target
EOF
sudo systemctl daemon-reload
sudo systemctl enable cpu-frequency.service
sudo systemctl start cpu-frequency.service
# Or via sysctl
echo 'MODULES=cpufreq_ondemand' | sudo tee -a /etc/default/grub
# Then update GRUB and reboot
Monitoreo de frecuencias de CPU
Monitoreo en tiempo real de frecuencia de CPU
# Watch CPU frequencies
watch -n 1 'cat /proc/cpuinfo | grep "cpu MHz"'
# All CPU frequencies
for i in {0..7}; do
echo "CPU$i: $(cat /sys/devices/system/cpu/cpu$i/cpufreq/scaling_cur_freq) kHz"
done
# Average frequency across CPUs
awk '/cpu MHz/ {sum+=$4; count++} END {print "Average: " sum/count " MHz"}' /proc/cpuinfo
# Monitor with turbostat (Intel)
sudo apt-get install -y linux-tools-common
sudo turbostat --interval 1
Estimación de consumo de potencia
# Estimate power from frequency/voltage
# Power = C * V^2 * f (approximately)
# Where C=capacitance, V=voltage, f=frequency
# Higher frequency:
# 3.5 GHz at turbo = ~150W per core
# 2.0 GHz at base = ~50W per core
# Monitor power consumption (if available)
cat /sys/class/powercap/intel-rapl:0/energy_uj
cat /sys/class/powercap/intel-rapl:1/energy_uj
Conclusión
El escalado de frecuencia de CPU proporciona herramientas poderosas para equilibrar eficiencia de rendimiento y potencia. La selección estratégica de gobernadores, gestión de turbo boost y configuración de C-state alinean el comportamiento de CPU con los requisitos de carga de trabajo. Comprender las compensaciones entre latencia, rendimiento y consumo de potencia permite que los equipos de infraestructura optimicen para casos de uso específicos. Los gobernadores automáticos modernos como schedutil a menudo proporcionan resultados casi óptimos sin sintonización manual, mientras que cargas de trabajo específicas se benefician de configuración explícita. El monitoreo regular asegura que el escalado de frecuencia funcione como se pretende, entregando tanto rendimiento como eficiencia en ambientes de producción.