Unix Systems for Modern Architectures
Unix Systems for Modern Architectures
Author: Curt Schimmel
Reviewer: Randolph Bentson (email@example.com)
“What is involved in a multiprocessor version of Linux?” has almost become a “Frequently Asked Question” in the Linux newsgroups. The answer is contained in Curt Schimmel's UNIX Systems for Modern Architectures.
Schimmel can speak from experience on this topic. He worked on Unix systems at AT&T Bell Laboratories and at Silicon Graphics, Inc., and has offered tutorials on symmetric multiprocessor Unix systems at USENIX and UKUUG. This book is an outgrowth of those tutorials.
At first glance, the book seems to offer too much detail about hardware for a programmer. But as one proceeds, one sees that understanding the subtleties of hardware-cache-bus-memory interactions is an essential component of “doing” a kernel for a multiprocessor system.
After a brief (17 page) description of Unix processes, another 130 pages are devoted to discussing uniprocessor cache systems. I was surprised and delighted to find out how hard it can be to get the right results. Fortunately, folks do seem to have done this right on the systems I've used.
With this foundation well established, the remainder of the book deals with the new domain of multiprocessor systems.
The keys to any such system are protecting shared data and efficient interprocess communication. Mutual exclusion mechanisms are cast in three forms - short term, medium term, and long term. We are shown how uniprocessor implementations of Unix depended on a single-threaded kernel and interrupt masking to protect shared data and, more importantly, we are shown how these methods are inappropriate for a multiprocessor system.
Schimmel shows how one can build locks for all three levels of mutual exclusion (and points out where they are needed in a typical Unix kernel). Although the master/slave scheme is straightforward to implement, it has much the flavor (and bottlenecks) of a uniprocessor system. The more promising symmetric multiprocessor scheme is not as easy to do correctly. The essence of the problem is finding the right granularity (or size) for the critical sections. Granularity that is either too large or too small can harm system performance. We are shown the analysis that leads to good designs.
The book concludes with more memory access and caching issues - this time with multi-processor systems. Some recent RISC chips have memory models which allow for stores and loads to be re-ordered from what the programmer intended, in order to gain performance. We are shown how RISC chips have mechanisms to force the correct results for implementing locks and accessing data in critical sections. Even when memory requests are issued in the order they were programmed, cache consistency is a serious issue in multiprocessor systems. The final chapters of the book address the interactions that must be dealt with by a serious system designer.
This book is written as a textbook, with questions and references at the end of each chapter. Selected questions have answers provided in an appendix. Another appendex summarizes a dozen popular chips found in Unix systems.
Randolph Bentson can be reached at: (firstname.lastname@example.org)
Fast/Flexible Linux OS Recovery
On Demand Now
In this live one-hour webinar, learn how to enhance your existing backup strategies for complete disaster recovery preparedness using Storix System Backup Administrator (SBAdmin), a highly flexible full-system recovery solution for UNIX and Linux systems.
Join Linux Journal's Shawn Powers and David Huffman, President/CEO, Storix, Inc.
Free to Linux Journal readers.Register Now!
|CentOS 6.8 Released||May 27, 2016|
|Secure Desktops with Qubes: Introduction||May 27, 2016|
|Chris Birchall's Re-Engineering Legacy Software (Manning Publications)||May 26, 2016|
|ServersCheck's Thermal Imaging Camera Sensor||May 25, 2016|
|Petros Koutoupis' RapidDisk||May 24, 2016|
|The Italian Army Switches to LibreOffice||May 23, 2016|
- Secure Desktops with Qubes: Introduction
- Download "Linux Management with Red Hat Satellite: Measuring Business Impact and ROI"
- Chris Birchall's Re-Engineering Legacy Software (Manning Publications)
- The Italian Army Switches to LibreOffice
- Linux Mint 18
- CentOS 6.8 Released
- Petros Koutoupis' RapidDisk
- ServersCheck's Thermal Imaging Camera Sensor
- Oracle vs. Google: Round 2
- The FBI and the Mozilla Foundation Lock Horns over Known Security Hole
Until recently, IBM’s Power Platform was looked upon as being the system that hosted IBM’s flavor of UNIX and proprietary operating system called IBM i. These servers often are found in medium-size businesses running ERP, CRM and financials for on-premise customers. By enabling the Power platform to run the Linux OS, IBM now has positioned Power to be the platform of choice for those already running Linux that are facing scalability issues, especially customers looking at analytics, big data or cloud computing.
￼Running Linux on IBM’s Power hardware offers some obvious benefits, including improved processing speed and memory bandwidth, inherent security, and simpler deployment and management. But if you look beyond the impressive architecture, you’ll also find an open ecosystem that has given rise to a strong, innovative community, as well as an inventory of system and network management applications that really help leverage the benefits offered by running Linux on Power.Get the Guide