SPEC CPU2017 Platform Settings for Lenovo Systems

Operating System Tuning Parameters

sched_cfs_bandwidth_slice_us
This OS setting controls the amount of run-time(bandwidth) transferred to a run queue from the task's control group bandwidth pool. Small values allow the global bandwidth to be shared in a fine-grained manner among tasks, larger values reduce transfer overhead. The default value is 5000 (ns).
sched_latency_ns
This OS setting configures targeted preemption latency for CPU bound tasks. The default value is 24000000 (ns).
sched_migration_cost_ns
Amount of time after the last execution that a task is considered to be "cache hot" in migration decisions. A "hot" task is less likely to be migrated to another CPU, so increasing this variable reduces task migrations. The default value is 500000 (ns).
sched_min_granularity_ns
This OS setting controls the minimal preemption granularity for CPU bound tasks. As the number of runnable tasks increases, CFS(Complete Fair Scheduler), the scheduler of the Linux kernel, decreases the timeslices of tasks. If the number of runnable tasks exceeds sched_latency_ns/sched_min_granularity_ns, the timeslice becomes number_of_running_tasks * sched_min_granularity_ns. The default value is 8000000 (ns).
sched_wakeup_granularity_ns
This OS setting controls the wake-up preemption granularity. Increasing this variable reduces wake-up preemption, reducing disturbance of compute bound tasks. Lowering it improves wake-up latency and throughput for latency critical tasks, particularly when a short duty cycle load component must compete with CPU bound components. The default value is 10000000 (ns).
numa_balancing
This OS setting controls automatic NUMA balancing on memory mapping and process placement. NUMA balancing incurs overhead for no benefit on workloads that are already bound to NUMA nodes. Possible settings: For more information see the numa_balancing entry in the Linux sysctl documentation.
Transparent Hugepages (THP)
THP is an abstraction layer that automates most aspects of creating, managing, and using huge pages. It is designed to hide much of the complexity in using huge pages from system administrators and developers. Huge pages increase the memory page size from 4 kilobytes to 2 megabytes. This provides 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.
THP usage is controlled by the sysfs setting /sys/kernel/mm/transparent_hugepage/enabled. Possible values: THP creation is controlled by the sysfs setting /sys/kernel/mm/transparent_hugepage/defrag. Possible values: An application that "always" requests THP often can benefit from waiting for an allocation until those huge pages can be assembled.
For more information see the Linux transparent hugepage documentation.
cpupower
The OS 'cpupower' utility is used to change CPU power governors settings. Available settings are:
tuned-adm
The tuned-adm tool is a commandline interface for switching between different tuning profiles available to the tuned tuning daemon 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:
dirty_background_ratio
Set through "echo 40 > /proc/sys/vm/dirty_background_ratio". This setting can help Linux disk caching and performance by setting the percentage of system memory that can be filled with dirty pages.
dirty_ratio
Set through "echo 8 > /proc/sys/vm/dirty_ratio". This setting is the absolute maximum amount of system memory that can be filled with dirty pages before everything must get committed to disk.
ksm/sleep_millisecs
Set through "echo 200 > /sys/kernel/mm/ksm/sleep_millisecs". This setting controls how many milliseconds the ksmd (KSM daemon) should sleep before the next scan.
swappiness
The swappiness value can range from 1 to 100. A value of 100 will cause the kernel to swap out inactive processes frequently in favor of file system performance, resulting in large disk cache sizes. A value of 1 tells the kernel to only swap processes to disk if absolutely necessary. This can be set through a command like "echo 1 > /proc/sys/vm/swappiness"
Zone Reclaim Mode
Zone reclaim allows the reclaiming of pages from a zone if the number of free pages falls below a watermark even if other zones still have enough pages available. Reclaiming a page can be more beneficial than taking the performance penalties that are associated with allocating a page on a remote zone, especially for NUMA machines. To tell the kernel to free local node memory rather than grabbing free memory from remote nodes, use a command like "echo 1 > /proc/sys/vm/zone_reclaim_mode"
Free the file system page cache
The command "echo 3> /proc/sys/vm/drop_caches" is used to free pagecache, dentries and inodes.

Firmware / BIOS / Microcode Settings

Choose Operating Mode: (Default="Efficiency -Favor Performance")
The average customer doesn't know the best way to set each individual power/performance feature for their specific environment. Because of this, a menu option is provided that can help a customer optimize the system for things such as minimum power usage/acoustic levels, maximum efficiency, Energy Star optimization, or maximum performance.
Page Policy:
Adaptive Open Page Policy can improve performance for applications with a highly localized memory access pattern; Closed Page Policy can benifit applications that access memory more randomly. Default is Closed.
CPU P-state Control:
Select the method used to control CPU P-states (performance states). "None" disables all P-states and the CPUs run at either their rated frequency or in turbo mode (if turbo is enabled). When [Legacy] is selected, the CPU P-states will be presented to the operating system (OS) and the OS power management (OSPM) will directly control which P-state is selected. With [Autonomous], the P-states are controlled fully by system hardware. No P-state support is required in the OS or VM. [Cooperative] is a combination of Legacy and Autonomous. The P-states are still controlled in hardware but the OS can provide hints to the hardware for P-state limits and the desired setting. With [Cooperative without Legacy], uses Intel native hardware p-states without Legacy p-state control (No OS controlled p-states). Starts with Autonomous mode until the OS swtiches to Cooperative. With [Cooperative with Legacy], uses Intel native hardware p-states but Legacy p-state control. Starts with Legacy p-states until the OS swtiches to Cooperative. When a preset mode is selected, the low-level settings are not changeable and will be grayed out. If user would like to change the settings, please choose [Custom Mode] in "Operating Mode" located under "System Setting" submenu. Default is Autonomous.
Memory Speed:
Select the desired memory speed. [Maximum Performance] mode maximizes performance. [Balanced] mode offers a balance between performance and power. [Minimal power] mode maximizes power savings. When a preset mode is selected, the low-level settings are not changeable and will be grayed out. If user would like to change the settings, please choose [Custom Mode] in "Operating Mode" located under "System Setting" submenu. Default is Maximum Performance.
C-States:
C-states reduce CPU idle power. There are three options in this mode: Legacy, Disabled. Default is Legacy. When a preset mode is selected, the low-level settings are not changeable and will be grayed out. If user would like to change the settings, please choose [Custom Mode] in "Operating Mode" located under "System Setting" submenu.
C1 Enhanced Mode:
Enabling C1E (C1 enhanced) state can save power by halting CPU cores that are idle. Default is Enabled.
Turbo Mode:
Enabling turbo mode can boost the overall CPU performance when all CPU cores are not being fully utilized. A CPU core can run above its rated frequency for a short perios of time when it is in turbo mode. When a preset mode is selected, the low-level settings are not changeable and will grayed out. If user would like to change the settings, please choose [Custom Mode] in "Operating Mode" located under "System Settings" submenu. Default is Enabled.
Hyper-Threading:
Enabling Hyper Threading let operating system addresses two virtual or logical cores for a physical presented core. Workloads can be shared between virtual or logical cores when possible. The main function of hyper-threading is to increase the number of independent instructions in the pipeline for using the processor resources more efficiently. Default is Enabled.
DCA:
DCA capable I/O devices such as network controllers can place data directly into the CPU cache, which improves response time. Default is Enabled.
Power/Performance Bias:
Power/Performance bias determines how aggressively the CPU will be power managed and placed into turbo. With [Platform Controlled], the system controls the setting. Selecting [OS Controlled] allows the operating system to control it. Not all OSes support this feature. When a preset mode is selected, the low-level settings are not changeable and will be grayed out. If user would like to change the settings, please choose [Custom Mode] in "Operating Mode" located under "System Setting" submenu. Default is Platform Controlled.
Platform Controlled Type:
Controls how aggressively the processor's Power Control Unit (PCU) will engage power management and how the CPU cores are placed into turbo mode. Default is [Efficiency-Favor Performance]. When a preset mode is selected, the low-level settings are not changeable and will be grayed out. If user would like to change the settings, please choose [Custom Mode] in "Operating Mode" located under "System Setting" submenu.
CPU Frequency Limits:
When the CPU Frequency Limit parameter is set to the Restrict Maximum Frequency setting, the maximum frequency (turbo, AVX, and non turbo) can be restricted to a frequency that is between the maximum turbo frequency for the CPU installed and 1.2GHz. This can be useful for synchronizing CPU task. Note, the max frequency for N+1 cores cannot be higher than N cores. If an illegal frequency is entered, it will automatically be limited to a legal value. If the CPU frequency limits are being controlled through application software, leave this menu item at the default ([Full turbo uplift]), please choose [Custom Mode] in "Operating Mode" and [Enable] in "Turbo Mode" located under "System Setting" submenu. Default is Full turbo uplift.
Uncore Frequency Scaling:
When enabled, the CPU uncore will dynamically change speed based on the workload. All miscellaneous logic inside the CPU package is considered the uncore. Default is Enabled.
MONITOR/MWAIT:
MONITOR/MWAIT instructions are used to engage C-states. Some operating systems will re-enable C-states even when they are disabled in setup. To prevent this, disable MONITOR/MWAIT. Please chkoose [Custom Mode] in "Operating Mode" and [Disabled] in "C-States" located under "System Setting" submenu. Default is Enabled.
Sub-NUMA Cluster (SNC):
Sub_NUMA Cluster (SNC) partitions the cores and last level cache (LLC) into clusters with each cluster bound to a set of memory controllers in the system, dividing each CPU package into 2 or 4 NUMA nodes. This can improve average latency to the last level cache and memory. Default is Disabled.
XPT Prefetcher
When enabled, enables a read request that is sent to the processor last level cache to speculatively issue a copy of that read request to the processor memory controller prefetcher to reduce latency. The performance benefit can vary so the end user must determine whether or not enabling the XPT prefetcher benefits their specific application environment. Default is Enabled.
UPI Prefetcher
When enabled, memory reads on the memory bus can be started earlier by the processor memory controller to reduce latency. The performance benefit can vary so the end user must determine whether or not enabling the UPI prefetcher benefits their specific application environment. Default is Enabled.
Patrol Scrub:
Enable/Disable "Patrol Scrub" which proactively searches the system memory to repair correctable errors. when [Enabled] is selected, Patrol Scrub would take effect at the end of POST. Default is Enabled.
DCU Streamer Prefetcher:
DCU (Level 1 Data Cache) streamer prefetcher is an L1 data cache prefetcher. Lightly threaded applications and some benchmarks can benefit from having the DCU streamer prefetcher enabled. Default setting is Enabled.
Stale AtoS
The in-memory directory has three states: invalid (I), snoopAll (A), and shared (S). Invalid (I) state means the data is clean and does not exist in any other socket`s cache. The snoopAll (A) state means the data may exist in another socket in exclusive or modified state. Shared (S) state means the data is clean and may be shared across one or more socket`s caches. When doing a read to memory, if the directory line is in the A state we must snoop all the other sockets because another socket may have the line in modified state. If this is the case, the snoop will return the modified data. However, it may be the case that a line is read in A state and all the snoops come back a miss. This can happen if another socket read the line earlier and then silently dropped it from its cache without modifying it. Values for this BIOS option can be: Stale AtoS may be beneficial in a workload where there are many cross-socket reads. Default is Auto.
LLC dead line alloc
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: Default is Enable.
Adjacent Cache Prefetch:
When enabled, fetches both cache lines that make up a 128 byte cache line pair even if the requested data is only in the first cache line. Lightly threaded applications and some benchmarks can benefit from having the adjcent cache line prefetch enabled. Default is Enabled.
DCU IP Prefetcher:
DCU IP Prefetcher is typically best left enabled for most environments. Some environments may benefit from having it disabled(e.g. Java). Default is Enabled.
Workload Configuration:
I/O sensitive should be used with expansion cards that require high I/O bandwidth when the CPU cores are idle to allow enough frequency for the workload. Default is Balanced.
Memory Power Management:
Allows the platform to put the memory into a lower power consumption state. Performance may be reduced. [Disabled] provides maximum performance but minimum power savings. [Automatic] is suitable for most applications. When a preset mode is selected, the low-level settings are not changeable and will grayed out. If user would like to change the settings, please choose [Custom Mode] in "Operating Mode" located under "System Settings" submenu. Default is Disabled.
UPI Link Disable:
Disabling one of the CPU UPI links can save power. If maximum performance is desired, all UPI links should be left enabled. When a preset mode is selected, the low-level settings are not changeable and will be grayed out. If user would like to change the settings, please choose [Custom Mode] in "Operating Mode" located under "System Setting" submenu. Note, for some highly NUMA optimized workoads, maximum performance may be achieved by setting 'Disabled 1 Link'. Default is Enabled ALL Links.
UPI Link Frequency:
Select the desired CPU UPI link frequency. Default is Maximum Performance. When a preset mode is selected, the low-level settings are not changeable and will be grayed out. If user would like to change the settings, please choose [Custom Mode] in "Operating Mode" located under "System Setting" submenu.
LLC Prefetch:
LLC prefetcher is an additional prefetch mechanism on the top of the existing prefetchers that prefetch data into the core DCU amd MLC. Enabling LLC Prefetch gives the core prefetcher the ability to prefetch data directly into the LLC without necessarily filling into the MLC. Default is Enabled.
AMP Prefetch:
Set to enable or disable MLC AMP prefetch (MSR 1A4h [4]). Some benchmarks can benefit from having this Mid-Level-Cache (MLC) prefetch enabled.