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George Neville-Neil - Understanding and Tuning SCHED_ULE
Source: BSDCan - The Technical BSD Conference
Added: 25 May 2009
Tags: bsdcan, bsdcan2009, presentation, freebsd, sched_ule, george neville-neil
Slides (228 Kb, 29 pages)
Understanding and Tuning SCHED_ULE
With the advent of widespread SMP and multicore CPU
architectures it was necessary to implement a new
scheduler in the FreeBSD operating system. The
SCHEDULE scheduler was added for the 5 series of
FreeBSD releases and has now matured to the point
where it is the default scheduler in the 7.1 release.
While scheduling processes was a difficult enough
task in the uniprocessor world, moving to multiple
processors, and multiple cores, has significantly
increased the number of problems that await engineers
who wish to squeeze every last ounce of performance
out of their system. This talk will cover the basic
design of SCHEDULE and focus a great deal of attention
on how to tune the scheduler for different workloads,
using the sysctl interfaces that have been provided
for that purpose.
Understanding and tuning a scheduler used to be
done only by operating systems designers and perhaps
a small minority of engineers focusing on esoteric
high performance systems. With the advent of
widespread multi-processor and multi-core architectures
it has become necessary for more users and
administrators to decide how to tune their systems
for the best performance. The SCHEDULE scheduler
in FreeBSD provides a set of sysctl interfaces for
tuning the scheduler at run time, but in order to
use these interfaces effectively the scheduling
process must first be understood. This presentation
will give an overview of how SCHEDULE works and
then will show several examples of tuning the system
with the interfaces provided.
The goal of modifying the scheduler's parameters
is to change the overall performance of programs
on the system. One of the first problems presented
to the person who wants to tune the scheduler is
how to measure the effects of their changes. Simply
tweaking the parameters and hoping that that will
help is not going to lead to good results. In our
recent experiments we have used the top(1) program
to measure our results.