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Linux Users of Victoria Presentation,Tues. July 11, 2000

Next Generation Linux: What Not to Do!

Neil J. Gunther

Performance Dynamics Consulting (sm)
Castro Valley, California 94552


The latest generation of commercial UNIXes (e.g., AIX, HPUX, and Solaris)offer facilities for automatically managing the consumption of system resources suchas processors, disks, and memory. This is accomplished by reengineering the generictime-share scheduler to become a so-called "fair-share" scheduler.This apparently simpler administrative "set it and forget it" approachto resource control belies the potential adverse impact on performance as measuredby user response time and service level targets. None of the commercial implementationsdiscuss these issues nor do they provide tools that are suitable for avoiding them.


In this talk, I will review the concept of fair-share scheduling and the motivationsbehind deploying it. Then, I will present several share allocation scenarios, basedon the open source modeling tool called PDQ,together with their surprising performance consequences. Finally, from considerationsemerges what is really needed. It's also good for Linux to be "behind"the bleeding edge in this case. Since I'll be referring to PDQ (Pretty DamnQuick) performance models,you might like to quickly review some of the ideas presented in my 1996LUV talk.


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