Hyper-threading and the Sun Fire[TM] V60x and V65x

Asset ID:	1-71-1003411.1
Update Date:	2010-01-01
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Solution Type Technical Instruction Sure

Solution 1003411.1 : Hyper-threading and the Sun Fire[TM] V60x and V65x

Related Items


Sun Fire V60x Server
 Sun Fire V65x Server

Related Categories


GCS>Sun Microsystems>Servers>x64 Servers

PreviouslyPublishedAs
204785

Description

Hyper-threading is a new technology that Intel has incorporated into the latest Pentium 4 desktop and Xeon server CPUs. Hyper-threading allows the scheduler to hand a CPU 2 separate program instructions simultaneously.

Hyper-Threading, sometimes also referred to as simultaneous multithreading (SMT), allows different threads to run simultaneously on different execution units within one physical processor.

Hyper-threading is not the same as having a multi-core CPU. Multi-core CPUs are many true CPUs mounted in the same casing, allowing much higher CPU densities. Both Sun and Intel have announced plans for multi-core (starting with dual-core) CPU products in the future.

Hyper-threading is an enhancement to the scheduler that allows the CPU to pretend to be multiple CPUs to optimize how instructions are processed.

This technology has its roots in development done by engineers who were working on incorporating it into future versions of the Alpha processor.

Steps to Follow
How do the Sun Fire V60x and V65x implement Hyper-threading.

Sun's latest x86-based servers, the Sun Fire V60x and V65x, use Intel Xeon processors that are Hyper-threading capable. However Hyper-threading is not enabled by default.

Should the customer wish to enable Hyper-threading, the process to do so is simple:

Press F2 while booting during the power-on self test (POST) to enter the BIOS configuration menu.
Using the down arrow key, scroll to Processor Settings then press the enter key.
Toggle the feature Hyper-threading(tm)using the enter and arrow keys.
Press the Esc key once to exit the Processor Settings menu.
Press the Left arrow key to highlight the Exit menu.
Press the Enter key to select Exit Saving Changes.
Press the Enter key again to confirm the new BIOS setting.
The system will continue booting with the new setting.

When can Hyper-threading improve application performance

Hyper-threading improves performance primarily for single applications that are multi-threaded or systems that run multiple services. The improvement is quoted as being anywhere up to 30% for heavily threaded applications, especially if they have been optimized to run on a Hyper-threading enabled CPU.

In some cases it may be more beneficial to have Hyper-threading disabled as most x86 applications today are typically not threaded or hyper-threading optimized. This is usually done through turning off Hyper-threading in the BIOS (this is done by default on the Sun Fire V60x and V65x). A couple of examples where this may be desirable:

For single-threaded dedicated function systems (most EDA, HPTC, rendering applications)

In systems that are optimized to run a single thread or process, like is often the case in High Performance Computing (HPC) applications, Hyper-threading can actually lead to a degradation in application performance (we have seen 5+ %).
For software that is not Hyper-threading aware and is licensed based on the number of CPUs.

Older operating systems may falsely interpret the Hyper-threading CPU as 2 physical CPUs. Even with a modern operating environment that properly recognizes it as 2 logical CPUs, applications need to be updated to understand the concept of logical processors. Otherwise applications that are licensed based on the number of physical CPUs may improperly assume that the operator has violated the license. In some cases the software may cease to function.

Which major x86 OSs make use of Hyper-threading today

Red Hat Linux 9
SuSE Linux 8.2
Red Flag Linux Desktop 4.0
Microsoft Windows 2003 Server (all versions)
Microsoft Windows XP (all versions)

The Solaris^[TM] operating system x86 team has stated that Hyper-threading support is under development, however no announcement has been made as to when Hyper-threading support will be released.

Where to go for more information

Intel - Pentium 4 with Hyper-threading Technology http://www.intel.com/homepage/land/hyperthreading.htm

Intel - Hyper-Threading Technology FAQ http://support.intel.com/support/platform/ht/faq.htm

NOTES:

The list above may not be all inclusive as new operating environments are constantly adopting Hyper-threading awareness.

Hyper-threading is a fairly recent technology and support for it is being refined in all of the operating environments mentioned below. For instance, while Hyper-threading was introduced during Linux kernel 2.4, improvements continue to be introduced and performance is expected to be much enhanced with the upcoming kernel 2.6 (or with backported patches to the stock 2.4 kernel). Because Hyper-threading is a recent kernel enhancement, distributions not running a fairly new version of the 2.4 kernel are not Hyper-threading aware and may recognize the CPU as being 2 physical CPUs or have other inconsistencies.

Likewise the Hyper-threading support in Windows 2003 is considered to be superior to that in Windows XP.

Product
Sun Fire V65x Server
Sun Fire V60x Server

Internal Comments

This article is original published in August 2003 Edition of
Technocrat.

http://onestop/technocrat/archive/html/aug4,2003.shtml#hyper

hyper-threading
Previously Published As
71205

Change History
Date: 2003-08-13
User Name: 97961
Action: Approved
Comment: Publishing. Drafted by KE for Technocrat author.
Version: 0
Date: 2003-08-13
User Name: 13484
Action: Approved
Comment: Technocrat article conversion done by KMO on behalf of the author.
Version: 0
Date: 2003-08-13
User Name: 13484
Action: Created
Comment:
Version: 0
Product_uuid
079e9bbc-0ee3-11d7-8c50-f1061905b56f|Sun Fire V65x Server
03728cec-0ee3-11d7-9be8-dd41f651e0a3|Sun Fire V60x Server

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