SPEC CPU2017 Platform Settings for Maginfra systems

Operating System Tuning Parameters

cpupower:

The OS 'cpupower' utility is used to change CPU power governors settings. Available settings are:

• Performance: Run the CPU at the maximum frequency.
• powersave(default): Run the CPU at the minimum frequency.
• ondemand: Scales the frequency dynamically according to current load. Jumps to the highest frequency and then possibly back off as the idle time increases.

drop_caches:

sysctl is used to change kernel parameters at run-time -w vm.drop_caches=3 - clears filesystem caches

SCALING_GOVERNOR:

Setting this environment variable to "performance" to enable cores to run at performance mode.

"scaling_governor" is a configuration file in Linux's "cpufreq" model. There are five mode in "scaling_governor" which are performance, powersave, userspace, ondemand, and conservative.

• Performance: Lock the CPU's frequency at top speed without adjusting dynamically,which may require additional power;
• Powersave: CPU will work at the minimum frequency;
• Userspace: Provides the corresponding interface for the user-mode application program to adjust the frequency of CPU;
• Ondemand: Quick dynamic adjustment of CPU frequency on demand, and will reach the maximum frequency;
• Conservative: Frequency will be adjusted on demand.

We use "cpupower frequency-set -g performance" to set this environment variable to "performance".

tuned-adm:

A commandline interface for switching between different tuning profiles available in supported Linux distributions. The distribution provided profiles are located in /usr/lib/tuned and the user defined profiles in /etc/tuned. To set a profile, one can issue the command "tuned-adm profile (profile_name)". Below are details about some relevant profiles.

• tuned-adm command line utility allows user to switch between user definable tuning profiles.[active, profile (name), off]
• throughput-performance: For typical throughput performance tuning. Disables power saving mechanisms and enables sysctl settings that improve the throughput performance of disk and network I/O. CPU governor is set to performance and CPU energy performance bias is set to performance. Disk readahead values are increased;
• latency-performance: For low latency performance tuning. Disables power saving mechanisms. CPU governor is set to performance and locked to the low C states. CPU energy performance bias to performance;
• balanced: Default profile provides balanced power saving and performance. It enables CPU and disk plugins of tuned and makes the conservative governor is active and also sets the CPU energy performance bias to normal. It also enables power saving on audio and graphics card;
• powersave: Maximal power saving for whole system. It sets the CPU governor to ondemand governor and energy performance bias to powersave. It also enable power saving on USB, SATA, audio and graphics card;

We use "tuned-adm profile throughput-performance" to set this environment variable to "throughput-performance".

Firmware / BIOS / Microcode Settings

SMT Mode:

Can be used to disable symmetric multithreading. To re-enable SMT, a POWER CYCLE is needed after selecting Enable..

• Enable: Enables simultaneous multithreading.
• Disable: Disables simultaneous multithreading so that only one thread or CPU instruction stream is run on a physical CPU core.

Determinism Slider:

This BIOS option allows for AGESA determinism to control performance.

• Performance: Provides predictable performance across all processors of the same type.
• Power: Maximizes performance within the power limits defined by cTDP and PPT.
• Auto (Default setting): Use AGESA default value for deterministic performance control.

cTDP Control:

This BIOS option is for "Configurable TDP (cTDP)", it allows user can set customized value for TDP. Available settings are:

• Auto: Use the fused TDP value.
• Manual(Default setting): Let user specifies customized TDP value.

cTDP:

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. The default cTDP value is set at a good balance between performance and energy efficiency.

SVM Mode:

This is CPU virtualization function. With SVM enabled you'll be able to install a virtual machine on your system. Values for this BIOS option can be: Enabled/Disabled. Current default is Enabled.

SR-IOV support:

In virtualization, single root input/output virtualization or SR-IOV is a specification that allows the isolation of the PCI Express resources for manageability and performance reasons. A single physical PCI Express can be shared on a virtual environment using the SR-IOV specification. If system has SR-IOV capable PCIe Devices, this option Enables or Disables Single Root IO Virtualization Support. Values for this BIOS option can be: Enabled/Disabled. Current default is Disabled.

NUMA nodes per socket:

Specifies the number of desired NUMA nodes per populated socket in the system:

• NPS1: Each physical processor is a NUMA node, and memory accesses are interleaved across all memory channels directly connected to the physical processor.
• NPS2: Each physical processor is two NUMA nodes, and memory accesses are interleaved across 4 memory channels.
• NPS4: Each physical processor is four NUMA nodes, and memory accesses are interleaved across 2 memory channels.
• Auto: Use AGESA default value. Current default is NPS1

Current default is Auto.

APBDIS:

Application Power Management (APM) allows the processor to provide maximum performance while remaining within the specified power delivery and removal envelope. APM dynamically monitors processor activity and generates an approximation of power consumption. If power consumption exceeds a defined power limit, a P-state limit is applied by APM hardware to reduce power consumption. APM ensures that average power consumption over a thermally significant time period remains at or below the defined power limit. Set APBDIS=1 will disable Data Fabric APM and the SOC P-state will be fixed. Available settings are:

• 0: Disable APBDIS.
• 1: Enable APBDIS.
• Auto (Default setting): Use default value for APBDIS. The current value is 0.

Fix SOC P-state:

To minimize variance or trade-off memory latency versus bandwidth, algorithm performance boost (APBDIS) can be set and specific hard-fused Data Fabric (SoC) P-states forced for optimized workloads sensitive to latency or throughput. Available settings are:

• P0: The highest SOC P-state.
• P1
• P2
• P3: The lowest SOC P-state.
• Auto (Default setting): Use AGESA default value.

ACPI SRAT L3 Cache as NUMA Domain:

Each L3 Cache will be exposed as a NUMA node when enabling ACPI SRAT L3 Cache as a NUMA node. On a dual processor system, with up to 8 L3 Caches per processor, this setting will expose 16 NUMA domains. Available settings are:

• Auto (Default setting): Disable this function.
• Enabled: Enable this function.

Package Power Limit Control:

This BIOS option allows user can set customized value for processor package power limit(PPT). Available settings are:

• Auto: Use the fused PPT.
• Manual(Default setting): User can set customized PPT.

DLWM Support:

Dynamic Link Width Management(DLWM) reduces xGMI lane width from x16 to x8 or x2 if xGMI links have limited traffic. DLWM feature is optimized to trade power between CPU core intensive workloads and I/O bandwidth intensiveworkloads. When link activity is above a threshold, DLWM will increase lane width from x8 to x16 at the cost of some delay, because the I/O die must disconnect the links, retrain them at the new speed and release the system back to functionality. Values for this BIOS option can be: Auto/Enabled/Disabled. Current default is Auto.(Use AGESA default value. Current is Enabled.)

Package Power Limit:

Set customize processor Package Power Limit (PPT) value to be used on all populated processors in the system. Current default value is 240 = Use the 240W PPT value. ***PPT will be used as the ASIC power limit***

IOMMU:

The Input-Output Memory Management Unit(IOMMU) provides several benefits and is required when using x2APIC. Enabling the IOMMU allows devices (such as the EPYC integrated SATA controller) to present separate IRQs for each attached device instead of one IRQ for the subsystem. The IOMMU also allows operating systems to provide additional protection for DMA capable I/O devices. Values for this BIOS option can be: Auto/Enabled/Disabled. Current default is Auto.(Use AGESA default value. Current is Enabled.)