SPEC CPU2017 Platform Settings for GIGA-BYTE

Operating System Tuning Parameters

kernel.randomize_va_space (ASLR)

This setting can be used to select the type of process address space randomization. Defaults differ based on whether the architecture supports ASLR, whether the kernel was built with the CONFIG_COMPAT_BRK option or not, or the kernel boot options used.
Possible settings:

• 0: Turn process address space randomization off.
• 1: Randomize addresses of mmap base, stack, and VDSO pages.
• 2: Additionally randomize the heap. (This is probably the default.)

Disabling ASLR can make process execution more deterministic and runtimes more consistent. For more information see the randomize_va_space entry in the Linux sysctl documentation.

drop_caches:

Writing to this will cause the kernel to drop clean caches, as well as reclaimable slab objects like dentries and inodes. Once dropped, their memory becomes free.

• To free pagecache: echo 1 > /proc/sys/vm/drop_caches
• To free reclaimable slab objects (includes dentries and inodes): echo 2 > /proc/sys/vm/drop_caches
• To free slab objects and pagecache: echo 3 > /proc/sys/vm/drop_caches

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.

Firmware / BIOS / Microcode Settings

Power Policy Quick Settings: (Default = Standard)

This BIOS option controls the performance or power save setting, user can use this item to change it. Values for this BIOS setting can be:

• Standard: BIOS default setting.
• Best Performance: Maximize the performance of the server.
• Energy Efficient: Maximize the power efficiency of the server.

TDP Control:(Default = Auto)

Auto = Use the fused TDP, Manual = User can set customized TDP. Values for this BIOS option can be: Auto/Manual. Configures the maximum power that the CPU will consume, up to the platform power limit (PPT). Valid values vary by CPU model. If value outside the valid range is set, the CPU will automatically adjust the value so that it does fall within the valid range. When increasing TDP, additional power will only be consumed up to the Package Power Limit (PPT), which may be less than the TDP setting.

TDP:(Default = 500)

Specifies the maximum power that each CPU package may consume in the system. The actual power limit is the maximum of the TDP. Valid settings are:

Model	Minimum TDP	Maximum TDP
EPYC 9965	450	500
EPYC 9755	450	500

PPT Control:(Default = Auto)

Auto = Use the fused PPT, Manual = User can set customized PPT. Values for this BIOS option can be: Auto/Manual. Configures the maximum power that the CPU will consume, up to the platform power limit (PPT). Valid values vary by CPU model. If value outside the valid range is set, the CPU will automatically adjust the value so that it does fall within the valid range. When increasing TDP, additional power will only be consumed up to the Package Power Limit (PPT), which may be less than the TDP setting.

PPT:(Default = 500)

Specifies the maximum power that each CPU package may consume in the system. The actual power limit is the maximum of the PPT. Valid settings are:

Model	Minimum TDP	Maximum TDP
EPYC 9965	450	500
EPYC 9755	450	500

SMT Mode: (Default = Enabled)

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.