Dell BIOS Tuning for HPC on 13th Generation Haswell Servers - Owner's Manual & User Guide

BIOS tuning for HPC on 13th Generation Haswell servers Garima Kochhar, September 2014

This blog discusses the performance and energy efficiency implications of BIOS tuning options available on the new Haswell-based servers for HPC workloads. Specifically we looked at memory snoop modes, performance profiles and Intel’s Hyper-Threading technology and their impact on HPC applications. This blog is part two of a three part series. Blog one provided some initial results on HPC applications and performance comparisons on these new servers and previous generations. The third blog in this series will compare performance and energy efficiency across different Haswell processor models.

We’re familiar with performance profiles including power management, Turbo Boost and C-states. Hyper-Threading or Logical Processor is a known feature as well. The new servers introduce three different memory snoop modes – Early Snoop, Home Snoop and Cluster On Die. Our interest was in quantifying the performance and power consumed across these different BIOS options.

The “System Profile Settings” category in the BIOS combines several performance and power related options into a “meta” option. Turbo Boost, C-states, C1E, CPU Power Management, Memory Frequency, Memory Patrol Scrub, Memory Refresh Rate, Uncore Frequency are some of the sub-options that are pre-set by this “meta” option. There are four pre-configured profiles, Performance Per Watt (DAPC), Performance Per Watt (OS), Performance and Dense Configuration, that can be used. The DAPC and OS profiles balance performance and energy efficiency options aiming for good performance while controlling the power consumption. With DAPC, the Power Management is handled by the Dell i DRAC and system level components. With the OS profile, the operating system controls the power management. In Linux this would be the cpuspeed service and cpufreq governors. The Performance profile optimizes for only performance – most power management options are turned off here. The Dense Configuration profile is aimed at dense memory configurations, memory patrol scrub is more frequent and the memory refresh rate is higher and Turbo Boost is disabled. Additionally if the four pre- set profiles do not meet the requirement, there is a fifth option “Custom” that allows each of the sub- options to be tuned individually. In this study we focus only on the DAPC and Performance profiles. Past studies have shown us that DAPC and OS perform similarly, and Dense Configuration performs lower for HPC workloads.

The Logical Processor feature is based on Intel® Hyper-Threading (HT) technology. HT enabled systems appear to the operating system as having twice as many processor cores as they actually do by ascribing two “logical” cores to each physical core. HT can improve performance by assigning threads to each logical core; logical cores execute their threads by sharing the physical cores’ resources.

Snoop Mode is a new category under Memory Setting. Coherence between sockets is maintained by way of “snooping” the other sockets. There are two mechanisms for maintaining coherence between sockets. Snoop broadcast (Snoopy) modes where the sockets are snooped for every memory transaction and directory support where some information is maintained in memory that gives guidance on whether there is a need to snoop.

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