SPEC CPU2017 software OS and BIOS Settings Descriptions for xFusion Platform systems

Operating System Tuning Parameters

Cpufreq setting

"cpupower frequency-set" provides a simplified mechanism to adjust processor frequencies when cpu frequency scaling is enabled in the OS. See the cpupower-frequency-set man page for details.Here is a brief description of options used in the config file. By default, settings are applied to all logical cpus in the system.Frequencies can be passed in Hz, kHz (default), MHz, GHz, or THz by postfixing the value with the desired unit name, without any space. Available frequencies and governors can be determined with "cpupower frequency-info".

Tmpfs filesystem setting

Tmpfs is a file system which keeps all files in virtual memory.A tmpfs file system will go to swap if memory pressure demands real memory for applications. This can have a very negative effect on the I/O load and system performance

Kernel Boot Parameter

nohz_full: This kernel option sets adaptive tick mode (NOHZ_FULL) to specified porcessors. Since the number of interrupts is reduced to ones per second, latency-sensitive applications can take advantage of it.

Firmware / BIOS / Microcode Settings

Hardware Prefetcher (Default = Enabled)

This BIOS option allows the enabling/disabling of a processor mechanism to prefetch data into the cache according to a pattern-recognition algorithm In some cases, setting this option to Disabled may improve performance. Users should only disable this option after performing application benchmarking to verify improved performance in their environment.

Turbo Mode (Default = Enabled)

Intel Turbo boost Technology, Enabling this option allows the processor cores to automatically increase its frequency and increasing performance if it is running below power, temperature.

Hyper-Threading (Default = Enabled)

Enabling this option allows to use processor resources more efficiently, enabling multiple threads to run on each core and increases processor throughput, improving overall performance on threaded software.

Power Policy (Default = Custom)

Values for this BIOS setting can be: Custom: Allows the user to setup all of the BIOS options according to their requirement. Performance: Maximize the performance of the server. Efficiency: Maximize the power efficiency of the server. Load Balance: The system's performance and power consumption will be adjusted automatically according to the loading.

CPU C6 Report (Default = Disabled)

Enable or disable reporting of the CPU C6 State (ACPI C3) to the OS.

C1E (Default = Disabled)

When set to Enabled, the processor is allowed to switch to nimimum performance and save power when idle.

Memory Patrol Scrub (Default = Enabled)

This option allows for correction of soft memory errors. Over the length of system runtime, the risk of producing multi-bit and uncorrected errors is reduced with this option. Values for this BIOS setting can be:

Enabled: Correction of soft memory errors can occur during runtime.

Disabled: Soft memory error correction is turned off during runtime.

IMC (Integrated memory controller) Interleaving (Default = Auto)

This BIOS option controls the interleaving between the Integrated Memory Controllers (IMCs), Memory could be interleaved across sockets, memory controllers, DDR channels, Ranks. Memory is interleaved for performance and thermal distribution.

If IMC Interleaving is set to 2-way, addresses will be interleaved between the two IMCs.

If IMC Interleaving is set to 1-way, there will be no interleaving.

If IMC Interleaving is set to auto, it depends on the SNC (Sub NUMA Clustering) setting, when SNC is set to enbaled, the IMC Interleaving will be 1-way interleave, SNC is set to disabled, the IMC Interleaving will be 2-way interleave.

If SNC is disabled, IMC Interleaving should be set to 2-way. If SNC is enabled, IMC Interleaving should be set to 1-way.

Sub NUMA Cluster(SNC)

SNC breaks up the last level cache (LLC) into disjoint clusters based on address range, with each cluster bound to a subset of the memory controllers in the system. SNC improves average latency to the LLC and memory. SNC is a replacement for the cluster on die (COD) feature found in previous processor families. For a multi-socketed system, all SNC clusters are mapped to unique NUMA (Non Uniform Memory Access) domains.

SNC AUTO supports 1-cluster or 2-clusters depending on IMC interleave. SNC and IMC interleave both AUTO will support 1-cluster 2-way IMC interleave.

SNC Enable supports Full SNC (2 clusters) and 1-way IMC interleave. Utilizes LLC capacity more efficiently and reduces latency due to core/IMC proximity. This may provide performance improvement on NUMA-aware operating systems.

SNC disable supports 1-cluster and 2-way IMC interleave, the LLC is treated as one cluster.

LLC Dead Line Allocation (Default = Enabled)

In some Intel CPU caching schemes, mid-level cache (MLC) evictions are filled into the last level cache (LLC). If a line is evicted from the MLC to the LLC, the core can flag the evicted MLC lines as "dead.” This means that the lines are not likely to be read again. This option allows dead lines to be dropped and never fill the LLC if the option is disabled.

Values for this BIOS option can be:

Disabled: Disabling this option can save space in the LLC by never filling MLC dead lines into the LLC.

Enabled: Opportunistically fill MLC dead lines in LLC, if space is available.

Last Level Cache (LLC) Prefetch (Default = Enabled)

This option configures the processor last level cache (LLC) prefetch feature as a result of the non-inclusive cache architecture. The LLC prefetcher exists on top of other prefetchers that can prefetch data into the core data cache unit (DCU) and mid-level cache (MLC). In some cases, setting this option to disabled can improve performance. Typically, setting this option to enable provides better performance.

Values for this BIOS option can be:

Disabled: Disables the LLC prefetcher. The other core prefetchers are unaffected.

Enabled: Gives the core prefetcher the ability to prefetch data directly to the LLC.

Xtended Prediction Table (XPT) Prefetch (Default = Auto)

The Xtended Prediction Table (XPT) prefetcher exists on top of other prefetchers that can prefetch data into the DCU, MLC, and LLC. The XPT prefetcher will issue a speculative DRAM read request in parallel to an LLC lookup. This prefetch bypasses the LLC, saving latency. In some cases, setting this option to disabled can improve performance. Typically, setting this option to enable provides better performance.

Values for this BIOS option can be:

Enabled: Allows a read request sent to the LLC to speculatively issue a copy of the read to DRAM.

Disabled: Read requests to the LLC are not allowed to send a speculative read to DRAM.

Adaptive Double Device Data Correction (ADDDC) Sparing (Default = Enabled)

Adaptive Double Device Data Correction (ADDDC), which is an enhanced feature to DDDC. This function is used to correct data errors on two memory particles, ADDDC still has single-particle multi-bit error correction capability after the first particle failure occurs and is replaced.

Values for this BIOS option can be:

Enabled: Enable the ADDDC Sparing function.

Disabled: Disable the ADDDC Sparing function.