CPU2017 Flag Description
Lenovo Global Technology ThinkSystem SR860 V3 (2.20 GHz, Intel Xeon Gold 6416H)

Copyright © 2016 Intel Corporation. All Rights Reserved.

Implicitly Included Flags

This section contains descriptions of flags that were included implicitly by other flags, but which do not have a permanent home at SPEC.

• • -O3
  • 

  • Enable O2 optimizations plus more aggressive optimizations, such as prefetching, scalar replacement, and loop and memory access transformations. Enable optimizations for maximum speed, such as:

    • Loop unrolling, including instruction scheduling
    • Code replication to eliminate branches
    • Padding the size of certain power-of-two arrays to allow more efficient cache use.
    
    

    On IA-32 and Intel EM64T processors, when O3 is used with options -ax or -x (Linux) or with options /Qax or /Qx (Windows), the compiler performs more aggressive data dependency analysis than for O2, which may result in longer compilation times. The O3 optimizations may not cause higher performance unless loop and memory access transformations take place. The optimizations may slow down code in some cases compared to O2 optimizations. The O3 option is recommended for applications that have loops that heavily use floating-point calculations and process large data sets.

  • Includes:
    • -O2
      • -O1
        • -funroll-loops
        • -fno-builtin
        • -mno-ieee-fp
        • -fomit-framepointer
        • -ffunction-sections
        • -ftz
• • -O2
  • 

  • Enable optimizations for speed. This is the generally recommended optimization level. This option also enables:
    - Inlining of intrinsics
    - Intra-file interprocedural optimizations, which include:
    - inlining
    - constant propagation
    - forward substitution
    - routine attribute propagation
    - variable address-taken analysis
    - dead static function elimination
    - removal of unreferenced variables
    - The following capabilities for performance gain:
    - constant propagation
    - copy propagation
    - dead-code elimination
    - global register allocation
    - global instruction scheduling and control speculation
    - loop unrolling
    - optimized code selection
    - partial redundancy elimination
    - strength reduction/induction variable simplification
    - variable renaming
    - exception handling optimizations
    - tail recursions
    - peephole optimizations
    - structure assignment lowering and optimizations
    - dead store elimination
    

  • Includes:
    • -O1
      • -funroll-loops
      • -fno-builtin
      • -mno-ieee-fp
      • -fomit-framepointer
      • -ffunction-sections
      • -ftz
• • -O1
  • 

  • Enable optimizations for speed and disables some optimizations that increase code size and affect speed.
    To limit code size, this option:

    • Enable global optimization; this includes data-flow analysis, code motion, strength reduction and test replacement, split-lifetime analysis, and instruction scheduling.
    • Disables intrinsic recognition and intrinsics inlining.

    The O1 option may improve performance for applications with very large code size, many branches, and execution time not dominated by code within loops.

    -O1 sets the following options:
    -funroll-loops0, -fno-builtin, -mno-ieee-fp, -fomit-framepointer, -ffunction-sections, -ftz
  • Includes:
    • -funroll-loops
    • -fno-builtin
    • -mno-ieee-fp
    • -fomit-framepointer
    • -ffunction-sections
    • -ftz
• • -funroll-loops
  • 

  • Tells the compiler the maximum number of times to unroll loops. For example -funroll-loops0 would disable unrolling of loops.

• • -fno-builtin
  • 

  • -fno-builtin disables inline expansion for all intrinsic functions.

• • -mno-ieee-fp
  • 

  • This option trades off floating-point precision for speed by removing the restriction to conform to the IEEE standard.

• • -fomit-framepointer
  • 

  • EBP is used as a general-purpose register in optimizations.

• • -ffunction-sections
  • 

  • Places each function in its own COMDAT section.

• • -ftz
  • 

  • Flushes denormal results to zero.

Commands and Options Used to Submit Benchmark Runs

submit= MYMASK=`printf '0x%x' $((1<<$SPECCOPYNUM))`; /usr/bin/taskset $MYMASK $command

When running multiple copies of benchmarks, the SPEC config file feature submit is used to cause individual jobs to be bound to specific processors. This specific submit command, using taskset, is used for Linux64 systems without numactl.
Here is a brief guide to understanding the specific command which will be found in the config file:

• /usr/bin/taskset [options] [mask] [pid | command [arg] ... ]:
  taskset is used to set or retreive the CPU affinity of a running process given its PID or to launch a new COMMAND with a given CPU affinity. The CPU affinity is represented as a bitmask, with the lowest order bit corresponding to the first logical CPU and highest order bit corresponding to the last logical CPU. When the taskset returns, it is guaranteed that the given program has been scheduled to a specific, legal CPU, as defined by the mask setting.
• [mask]: The bitmask (in hexadecimal) corresponding to a specific SPECCOPYNUM. The specific example above, computes this mask value in the variable $MYMASK. The value of this mask for the first copy of a rate run will be 0x00000001, for the second copy of the rate will be 0x00000002 etc. Thus, the first copy of the rate run will have a CPU affinity of CPU0, the second copy will have the affinity CPU1 etc.
• $command: Program to be started, in this case, the benchmark instance to be started.

submit= numactl --localalloc --physcpubind=$SPECCOPYNUM $command

When running multiple copies of benchmarks, the SPEC config file feature submit is used to cause individual jobs to be bound to specific processors. This specific submit command is used for Linux64 systems with support for numactl.
Here is a brief guide to understanding the specific command which will be found in the config file:

• syntax: numactl [--interleave=nodes] [--preferred=node] [--physcpubind=cpus] [--cpunodebind=nodes] [--membind=nodes] [--localalloc] command args ...
• numactl runs processes with a specific NUMA scheduling or memory placement policy. The policy is set for a command and inherited by all of its children.
• "--localalloc" instructs numactl to keep a process memory on the local node while "-m" specifies which node(s) to place a process memory.
• "--physcpubind" specifies which core(s) to bind the process. In this case, copy 0 is bound to processor 0 etc.
• For full details on using numactl, please refer to your Linux documentation, 'man numactl'

Shell, Environment, and Other Software Settings

numactl --interleave=all "runspec command"

Launching a process with numactl --interleave=all sets the memory interleave policy so that memory will be allocated using round robin on nodes. When memory cannot be allocated on the current interleave target fall back to other nodes.

KMP_STACKSIZE

Specify stack size to be allocated for each thread.

KMP_AFFINITY

Syntax: KMP_AFFINITY=[<modifier>,...]<type>[,<permute>][,<offset>]
The value for the environment variable KMP_AFFINITY affects how the threads from an auto-parallelized program are scheduled across processors.
It applies to binaries built with -qopenmp and -parallel (Linux and Mac OS X) or /Qopenmp and /Qparallel (Windows).
modifier:
    granularity=fine Causes each OpenMP thread to be bound to a single thread context.
type:
    compact Specifying compact assigns the OpenMP thread <n>+1 to a free thread context as close as possible to the thread context where the <n> OpenMP thread was placed.
    scatter Specifying scatter distributes the threads as evenly as possible across the entire system.
permute: The permute specifier is an integer value controls which levels are most significant when sorting the machine topology map. A value for permute forces the mappings to make the specified number of most significant levels of the sort the least significant, and it inverts the order of significance.
offset: The offset specifier indicates the starting position for thread assignment.

Please see the Thread Affinity Interface article in the Intel Composer XE Documentation for more details.

Example: KMP_AFFINITY=granularity=fine,scatter
Specifying granularity=fine selects the finest granularity level and causes each OpenMP or auto-par thread to be bound to a single thread context.
This ensures that there is only one thread per core on cores supporting HyperThreading Technology
Specifying scatter distributes the threads as evenly as possible across the entire system.
Hence a combination of these two options, will spread the threads evenly across sockets, with one thread per physical core.

Example: KMP_AFFINITY=compact,1,0
Specifying compact will assign the n+1 thread to a free thread context as close as possible to thread n.
A default granularity=core is implied if no granularity is explicitly specified.
Specifying 1,0 sets permute and offset values of the thread assignment.
With a permute value of 1, thread n+1 is assigned to a consecutive core. With an offset of 0, the process's first thread 0 will be assigned to thread 0.
The same behavior is exhibited in a multisocket system.

OMP_NUM_THREADS

Sets the maximum number of threads to use for OpenMP* parallel regions if no other value is specified in the application. This environment variable applies to both -qopenmp and -parallel (Linux and Mac OS X) or /Qopenmp and /Qparallel (Windows). Example syntax on a Linux system with 8 cores: export OMP_NUM_THREADS=8

Set stack size to unlimited

The command "ulimit -s unlimited" is used to set the stack size limit to unlimited.

Free the file system page cache

The command "echo 3> /proc/sys/vm/drop_caches" is used to free up the filesystem page cache as well as reclaimable slab objects like dentries and inodes.

Red Hat Specific features

Transparent Huge Pages

On RedHat EL 6 and later, 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.
Hugepages are used by default unless the /sys/kernel/mm/redhat_transparent_hugepage/enabled field is changed from its RedHat EL6 default of 'always'.

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:

• 0: disables this feature
• 1: enables the feature (this is the default)

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:

• never: entirely disable THP usage.
• madvise: enable THP usage only inside regions marked MADV_HUGEPAGE using madvise(3).
• always: enable THP usage system-wide. This is the default.

THP creation is controlled by the sysfs setting /sys/kernel/mm/transparent_hugepage/defrag. Possible values:

• never: if no THP are available to satisfy a request, do not attempt to make any.
• defer: an allocation requesting THP when none are available get normal pages while requesting THP creation in the background.
• defer+madvise: acts like "always", but only for allocations in regions marked MADV_HUGEPAGE using madvise(3); for all other regions it's like "defer".
• madvise: acts like "always", but only for allocations in regions marked MADV_HUGEPAGE using madvise(3). This is the default.
• always: an allocation requesting THP when none are available will stall until some are made.

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:

• Performance: Run the CPU at the maximum frequency.
• powersave: Run the CPU at the minimum frequency.
• ondemand: Scales the frequency dynamically according to current load.

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:

• throughput-performance: Server profile for typical throughput tuning. This profile disables tuned and ktune power saving features, enables sysctl settings that may improve disk and network IO throughput performance, switches to the deadline scheduler, and sets the CPU governor to performance.
• latency-performance: Server profile for typical latency tuning. This profile disables tuned and ktune power saving features, enables the deadline IO scheduler, and sets the CPU governor to performance.
• enterprise-storage: Server profile to high disk throughput tuning. This profile disables tuned and ktune power saving features, enables the deadline IO scheduler, enables hugepages and disables disk barriers, increases disk readahead values, and sets the CPU governor to performance

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.

• "Minimal Power" mode strives to minimize the absolute power consumption of the system while it is operating. The tradeoff is that performance may be reduced in this mode depending on the application that is running.
• "Efficiency -Favor Power" mode maximizes the performance/watt efficiency with a bias towards power savings. It provides the best features for reducing power and increasing performance in applications where maximum bus speeds are not critical. It is expected that this will be the favored mode for SPECpower testing. "Efficiency -Favor Power" mode maintains backwards compatibility with systems that included the preset operating modes before Energy Star for servers was released.
• "Efficiency -Favor Performance" mode optimizes the performance/watt efficiency with a bias towards performance. It is the favored mode for Energy Star. Note that this mode is slightly different than "Efficiency -Favor Power" mode. In "Efficiency - Favor Performance" mode, no bus speeds are derated as they are in "Efficiency -Favor Power" mode. "Efficiency -Favor Performance" mode is the default mode.
• "Maximum Performance" mode will maximize the absolute performance of the system without regard for power. In this mode, power consumption is a don't care. Things like fan speed and heat output of the system may increase in addition to power consumption. Efficiency of the system may go down in this mode, but the absolute performance may increase depending on the workload that is running.
• A fifth setting, [Custom Mode], may be selected after any of the other 4 presets allowing low-level settings, which otherwise are preset and unchangeable, to be individually modified

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 two options in this mode: Legacy, Disabled. Default is Legacy.

• Legacy: When [Legacy] is selected, the operating system initiates the C-state transitions. For E5/E7 CPUs, ACPI C1/C2/C3 map to Intel C1/C3/C6. For 6500/7500 CPUs, ACPI C1/C3 map to Intel C1/C3 (ACPI C2 is not available). Some OS SW may defeat the ACPI mapping (e.g. intel_idle driver).
• Disabled: When "Disabled" is selected, only C0 and C1 are used by the OS. C1 gets enabled automatically when an OS autohalts.

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].

• Maximum Performance: Turbo mode can be engaged opportunistically before it is requested and uncore power management features (Memory, UPI, C-state demotion, I/O bandwidth limit and UFS) are aggressively disabled.
• Efficiency-Favor Performance:Turbo is quickly engaged but not opportunistically. Some light uncore and UPI power management features are engaged to provide low cost power savings with an overall weighting towards per core and per package performance.
• Efficiency-Favor Power:Turbo is engaged more slowly but uncore and UPI power management policies are quickly engaged to balance the systems towards power savings.
• Minimal Power:Turbo is not engaged and aggressive power management policies on the uncore and UPI are engaged to drive lowest performance / watt.

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.

• Disabled:the processor socket is treated as one cluster. No partitioning occurs.
• SNC2:each socket is divided into two groups, each with its own cores, LLC, and memory controller. System address is divided into two regions, one for each SNC. Required memory configuration to be left/right symmetric.
• SNC4:each socket is divided into four groups, each with its own cores, LLC, and memory controller. System address is divided into four regions, one for each SNC. Required memory configuration to be fully symmetric (left/right and top/bottom).

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:

• Disable: Disabling this option allows the feature to process memory directory states as described above.
• Enable: In the situation where a line in A state returns only snoop misses, the line will transition to S state. That way, subsequent reads to the line will encounter it in S state and not have to snoop, saving latency and snoop bandwidth.

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:

• Disable: Disabling this option can save space in the LLC by never filling MLC dead lines into the LLC.
• Enable: Opportunistically fill MLC dead lines in LLC, if space is available.

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:

A processor L1 instruction cache prefetcher that uses a predictive instruction prefetching scheme. This setting fetches the next cache line into the L1 data cache if there is a sequential load history of cache line accesses. The next cache line is fetched from either L2 or main memory.

• Enabled: When enabled, this parameter fetches the next cache line into the L1 data cache if there is a sequential load history of cache line accesses.
• Disabled: Experiments have been run selectively disabling the prefetchers one at a time and performance is improved when disabled.

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.

• Maximum Performance: maximizes performance.
• Balanced: offers a balance between performance and power.
• Minimal Power: 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.

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:

The Adaptive Multipath Probability (AMP) prefetch is a new data prefetch mechanism for the Golden Cove architecture. The AMP prefetch operates alongside the pre-existing L2 prefetch mechanisms: the L2 streamer and the L2 spatial prefetchers. Set to enable or disable MLC AMP prefetch (MSR 1A4h [4]). Some benchmarks can benefit from having this Mid-Level-Cache (MLC) AMP prefetch enabled. Default is Disable.

Optimized Power Mode:

The feature can save power while having minimal impact on performance for certain workloads that tend to run 30-40% CPU utilization.

• Enable: Enable Fast C1E, fix the uncore max frequency to 2.2GHz, set the active idle uncore frequency to 1.4GHz, and set the utilization point (UP) = 6.
• Disable (default): Disable Fast C1E, set the uncore max frequency to 2.5GHz, set the active idle uncore frequency to default, set the ubilization point (UP) = 0.

Memory Hierarchy:

In a system with High Bandwidth Memory and regular DDR memory,

• Flat: Flat mode means both High Bandwidth Memory and DDR memory are used as contiguous address space.
• Cache: Cache mode means acts as a buffer for the DDR memory.

If Cache mode configuration fails, or system only has High Bandwidth Memory, then the system will fail back to Flat mode. Default is Flat.

HBM Refresh Mode:

• Disabled: Disable refresh mode, same as Single.
• Auto (default): Support all refresh mode, could save power, lower system noise level and is useful to mitigate rowhammer issue, but that might have a performance impact.
• Single: Force single refresh.
• Double: Force double refresh, could save power, lower system noise level and is useful to mitigate rowhammer issue, but that might have a performance impact.

SNC2 is not supported on High Bandwidth Memory (HBM) processors i.e., Intel Xeon CPU Max Series SKU Stack.

Flag description origin markings:

	Indicates that the flag description came from the user flags file.
	Indicates that the flag description came from the suite-wide flags file.
	Indicates that the flag description came from a per-benchmark flags file.

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Copyright 2017-2023 Standard Performance Evaluation Corporation
Tested with SPEC CPU2017 v1.1.9.
Report generated on 2023-09-27 09:37:41 by SPEC CPU2017 flags formatter v5178.