Somebody Still Uses Assembly Language?
Typically, even for device drivers, Linux developers do not use assembly language. Hence, it is particularly revealing to examine those very few parts of the kernel which are written in assembly language. These can be found within the Linux distributions with the command:
find -name *.S
entered from the root directory. Of particular interest are these:
bootsect.S (Intel style instructions)
setup.S (Intel style)
head.S (AT&T style)
These are heavily commented, but additional guidance can be found in the Intel documentation and in Alessandro Rubini's Tour of the Linux Kernel Source, found in the Kernel Hacker's Guide. These modules do the first portions of system initialization, a process which is completed by C routines. Once they have been executed, the assembly language routines are done. Another module of interest is entry.S (AT&T style) whose tasks are ongoing. In particular, it contains low level routines for handling system calls and faults.
This material should help interested readers start their own investigations of the Intel 80x86 (x >= 3) architecture and the Linux kernel. Much can then be learned about such topics as operating modes, memory management, and building the various descriptor tables.
Richard A. Sevenich is a Professor of Computer Science at Eastern Washington University in Cheney, Washington. His original enthusiasm for Linux was derived in part from the fact that its development had been driven by user needs rather than by marketing hype. He can be reached at firstname.lastname@example.org.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
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With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide