SPEC CPU2017 Flag Description for Quanta Computer Inc.

Operating System Tuning Parameters

OS Tuning


Used to set user limits of system-wide resources. Provides control over resources available to the shell and processes started by it. Some common ulimit commands may include:

Disabling Linux services:

Certain Linux services may be disabled to minimize tasks that may consume CPU cycles.


Disabled through "service irqbalance stop". Depending on the workload involved, the irqbalance service reassigns various IRQ's to system CPUs. Though this service might help in some situations, disabling it can also help environments which need to minimize or eliminate latency to more quickly respond to events.

Performance Governors (Linux):

In-kernel CPU frequency governors are pre-configured power schemes for the CPU. The CPUfreq governors use P-states to change frequencies and lower power consumption. The dynamic governors can switch between CPU frequencies, based on CPU utilization to allow for power savings while not sacrificing performance.

Other options beside a generic performance governor can be set, such as the Performance governor and Powersave governor:

--governor , -g

The governor defines the power characteristics of the system CPU, which in turn affects CPU performance. Each governor has its own unique behavior, purpose, and suitability in terms of workload.

On many Linux systems one can set the governor for all CPUs through the cpupower utility with following commands:

Tuning Kernel parameters:

The following Linux Kernel parameters were tuned to better optimize performance of some areas of the system:


The tuned-adm tool is a commandline interface for switching between different tuning profiles available to the tuned tuning daeomn available in supported Linux distros. The default configuration file is located in /etc/tuned.conf and the supported profiles can be found in /etc/tune-profiles.

Some profiles that may be available by default include: default, desktop-powersave, server-powersave, laptop-ac-powersave, laptop-battery-powersave, spindown-disk, throughput-performance, latency-performance, enterprise-storage

To set a profile, one can issue the command "tuned-adm profile (profile_name)". Here are details about relevant profiles.

Transparent Huge Pages (THP):

THP is an abstraction layer that automates most aspects of creating, managing, and using huge pages. THP is designed to hide much of the complexity in using huge pages from system administrators and developers, as normal huge pages must be assigned at boot time, can be difficult to manage manually, and often require significant changes to code in order to be used effectively. Transparent Hugepages increase the memory page size from 4 kilobytes to 2 megabytes. Transparent Hugepages provide significant performance advantages on systems with highly contended resources and large 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. Most recent Linux OS releases have THP enabled by default.

Linux Huge Page settings:

If you need finer control and manually set the Huge Pages you can follow the below steps:

Note that further information about huge pages may be found in your Linux documentation file: /usr/src/linux/Documentation/vm/hugetlbpage.txt

Firmware / BIOS / Microcode Settings

Determinism Control:
This BIOS option allows user to choose AGESA determinism control. Available settings are:
Determinism Slider:
Selects the determinism mode for the CPU:
cTDP Control(Configurable TDP):
TDP is an acronym for “Thermal Design Power.” TDP is the recommended target for power used when designing the cooling capacity for a server. EPYC processors are able to control this target power consumption within certain limits. This capability is referred to as “configurable TDP” or "cTDP." cTDP can be used to reduce power consumption for greater efficiency, or in some cases, increase power consumption above the default value to provide additional performance. cTDP is controlled using a BIOS option.
The default EPYC cTDP value corresponds with the microprocessor’s nominal TDP. For the EPYC 7601, the default value is 180W. The default cTDP value is set at a good balance between performance and energy efficiency. The EPYC 7601 cTDP can be reduced as low as 165W, which will minimize the power consumption for the processor under load, but at the expense of peak performance. Increasing the EPYC 7601 cTDP to 200W will maximize peak performance by allowing the CPU to maintain higher dynamic clock speeds, but will make the microprocessor less energy efficient. Note that at maximum cTDP, the CPU thermal solution must be capable of dissipating at least 200W or the EPYC 7601 processor might engage in thermal throttling under load.
The available cTDP ranges for each EPYC model are in the table below:
Model Nominal TDP Minimum cTDP Maximum cTDP**
EPYC 7742 225 225 240
EPYC 7702 200 165 200
EPYC 7702P 200 165 200
EPYC 7601 180 165 200
EPYC 7551 180 165 200
EPYC 7502 180 165 200
EPYC 7502P 180 165 200
EPYC 7501 155/170 135 155/170*
EPYC 7451 180 165 200
EPYC 7402 180 165 200
EPYC 7402P 180 165 200
EPYC 7401 155/170 135 155/170*
EPYC 7351 155/170 135 155/170*
EPYC 7302 155 155 180
EPYC 7302P 155 155 180
EPYC 7301 155/170 135 155/170*
EPYC 7281 155/170 135 155/170*
EPYC 7252 120 120 150
EPYC 7252P 120 120 150
EPYC 7251 120 105 120
*Max TDP is 170W when DDR4 is operating at 2667 MT/sec, or 155W when DDR4 is operating at lower frequencies.
** cTDP must remain below the thermal solution design parameters or thermal throttling could be frequently encountered.
Package Power Limit (PPT) Control:
Specifies the maximum power that each CPU package may consume in the system. The actual power limit is the maximum of the Package Power Limit and cTDP. Available settings are:
NUMA nodes per socket (NPS):
Non-Uniform Memory Architecture (NUMA) enables the CPU cores to access memory via NUMA domains / nodes. Users can specify the number of desired NUMA nodes per populated socket in the system:
ACPI SRAT L3 Cache as NUMA Domain:
Enable the option to report each L3 cache as a NUMA domain to BIOS ACPI System Resource Affinity Table (SRAT):
SMT Control:
Can be used to disable symmetric multithreading. To re-enable SMT, a POWER CYCLE is needed after selecting the 'Auto' option. WARNING - S3 is NOT SUPPORTED on systems where SMT is disabled.
Enable: Enables the I/O Memory Management Unit (IOMMU), which extends the AMD64 system architecture by adding support for address translation and system memory access protection on DMA transfers from peripheral devices.
APBDIS is an IO Boost disable on uncore. For any system user that needs to block these uncore optimizations that are impacting base core clock speed, we are exposing a method to disable this behavior called APBDis. This locks the fabric clock to the non-boosted speeds. Available settings are:

Last updated Dec. 19, 2019.