OS Tuning
Minimal Installation of OS
Select only test related features when installing the operating system, which may cause many services uninstalled and thus may reduce the consumption of resources by the operation system itself.In accordance with the following ways to install operating system:
ulimit -s [n | unlimited] (Linux)
Sets the stack size to n kbytes, or unlimited to allow the stack size to grow without limit.
Tmpfs Filesystem Setting
Tmpfs is a file system on which everything is kept in virtual memory and no files will be created on the hard drive; the tmpfs will used swap space as backing store in case of low memory situations. This feature has a much negative effect on the I/O load and system performance.
Transparent HugePages
Transparent HugePages increase the memory page size from 4KB to 2MB. This feature provide significant performance advantages on systems with highly contended resources and the memory workloads. If memory utilization is too high or memory is badly fragmented which prevents hugepages being allocated, the kernel will assign smaller 4K pages instead.
On RHEL6 and later, Transparent Hugepages are used by default if /sys/kernel/mm/redhat_transparent_hugepage/enabled is set to always. The default value is always. On SUSE SLES11 and later and on NLAS V7U2, Transparent Hugepages are used by default if /sys/kernel/mm/transparent_hugepages/enabled is set to always. The default value is always.
Power Technology
This BIOS switch allows 3 options:"Disable", "Energy Efficient" and "Custom". "Energy Efficent" is the default value and it's for power saving. "Custom" is for personal customization and only when the switch is set as this value, the submemus, including "CPU HWPM State Control","CPU C State Control","CPU T State Control" and "CPU advanced PM Tuning" are open for configuring.
Enable CPU HWPM
This switch is included in the "CPU HWPM State Control" menu. It allows 3 values:"Disable","HWPM NATIVE MODE", "HWPM OOB MODE". Default is "Disable". Disable this option will help to improve the performance of system under test.
Package C State limit
This switch is included in "CPU C State Control" menu.It allows 4 values:"C0/C1 state", "C2 state", "C6(non Retention) state" and "C6(Retention) state". Default is "C6(Retention) state", which causes the CPU to enter a low-power mode when the CPU is idle. When set as "C0/C1 state", all of the cores are locked at the maxium performance and will cause a large consumption of power.
Enhanced Halt State (C1E)
This switch is included in "CPU C State Control" menu.Enabling this option which is the default allows the processor to transmit to its minimum frequency when entering the power state C1. If the switch is disabled the CPU stays at its maximum frequency in C1. Because of the increase of power consumption users should only select this option after performing application benchmarking to verify improved performance in their environment.
ACPI T-States
This switch is included in "CPU T State Control" menu. Enable / Disable this switch will activate/inactivate CPU throttling by operating system.Throttling reduces power consumption.The default value is "Enable".Disable this feature will contribute to high performance but may also cause high power consumption.
Energy Performance BIAS Setting.
This BIOS switch is included in the "Energy Perf BIAS" menu, which is a submenu of "CPU advanced PM Tuning". It allows 4 options: "Balanced performance", "Performance", "Balanced Power" and "Power". The default is "Balanced Performance", which has been optimized to maximum power savings with minimal impact on performance. "Performance" disables all power management options with any impact on performance. "Balanced Power" is optimized for power efficiency and "Power" for power savings.The two options "Balanced Performance" and "Balanced Power" should always be the first choice as both options optimize the efficiency of the system. In cases where the performance is not sufficient or the power consumption is too high the two options "Performance" or "Power" could be an alternative.
Turbo Mode:
Enabling turbo mode can boost the overall CPU performance when all CPU cores are not being fully utilized.
Hyper-threading:
This BIOS setting enables/disables Intel's Hyper-Threading (HT) Technology. With HT Technology, the operating system can execute two threads in parallel within each processor core.
NUMA:
This BIOS option sets memory accessing mode. NUMA is as Non Uniform Memory Access. If this option is enabled, each CPU chip can only access memory within its own node.
COD Enable
This switch could be found by the following path: "Chipset Configuration"->"North Bridge"->"QPI Configuration"->"QPI General Configuration"->"COD Enable". This switch allows 3 values: "Disable","Enable","Auto". Default is "Auto", which is equally to"Disable". When enable this option, the system will work on "Cluster on Die" mode, which logically splits a socket into 2 NUMA domains that are exposed to the OS with half the amount of cores and LLC assigned to each NUMA domain in a socket. This mode utilizes an on-die directory cache in memory directory bits to determine whether a snoop needs to be sent. Use this mode for highly NUMA optimized workloads to get the lowest local memory latency and highest local memory bandwidth for NUMA workloads.
Fan Mode
This option is designed in Baseboard Management Controller and it could be seen when open BMC homepage in a browser. This switch allows 3 options to set:"Set Fan to Standard Speed", "Set Fan to Full Speed", "Set Fan to HeavyIO Speed". And default is "Set Fan to Standard Speed".