User Manual

PerformanceRev 2.1-1.0.6
Mellanox Technologies
132
7.2.4.1 Setting the Scaling Governor
If the following modules are loaded, CPU scaling is supported, and you can improve perfor-
mance by setting the scaling mode to performance:
•
freq_table
• acpi_cpufreq: this module is architecture dependent.
It is also recommended to disable the module cpuspeed; this module is also architecture depen-
dent.
 To set the scaling mode to performance, use:
 To disable cpuspeed, use:
7.2.4.2 Kernel Idle Loop Tuning
The mlx4_en kernel module has an optional parameter that can tune the kernel idle loop for bet-
ter latency
. This will improve the CPU wake up time but may result in higher power consump-
tion.
To tune the kernel idle loop, set the following options in the
/etc/modprobe.d/mlx4.conf
file:
• For MLNX_OFED 2.0.x
• For MLNX_EN 1.5.10
7.2.4.3 OS Controlled Power Management
Some operating systems can override BIOS power management configuration and enable c-
states by default, which results in a higher latency
.
 To resolve the high latency issue, please follow the instructions below:
1. Edit the /boot/grub/grub.conf file or any other bootloader configuration file.
2. Add the following kernel parameters to the bootloader command.
intel_idle.max_cstate=0 processor.max_cstate=1
3. Reboot the system.
Example:
# echo performance > /sys/devices/system/cpu/cpu7/cpufreq/scaling_governor
# service cpuspeed stop
options mlx4_core enable_sys_tune=1
options mlx4_en enable_sys_tune=1
title RH6.2x64
root (hd0,0)
kernel /vmlinuz-RH6.2x64-2.6.32-220.el6.x86_64
root=UUID=817c207b-c0e8-4ed9-9c33-c589c0bb566f console=tty0
console=ttyS0,115200n8 rhgb intel_idle.max_cstate=0 processor.max_cstate=1