
Tweak Your Kernel Without Recompiling #91
Chapter 10, Kernel
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273
HACK
database also runs faster when you give it more memory to cache indexes
and data. So, when I am running an intense database program or happen to
be building a large program in the background, I reset the watermark to
33%, which allows the data cache-intensive applications to run at a decent
pace without having one or more desktop applications become totally unus-
able. Here is how to change this watermark in a running CKO kernel:
# echo "33" > /proc/sys/vm/mapped
# echo "66" > /proc/sys/vm/mapped
schedtool and Isochronous Scheduling
The CKO kernel also allows you to launch applications with isochronous
scheduling. Not all applications respond correctly to this technique, but
those that do start at a high priority and then drop priority faster than nor-
mal. This guarantees that when they “wake up,” they’ll do so quickly, but
they won’t retain such a high priority that they starve the rest of the system
and bring all other tasks to a crawl.
You need a special tool to use this feature. If your Linux distribution doesn’t
provide the
schedtool package or something with a similar name, you can get
the source code from http://freequaos.host.sk/schedtool/ and compile it your-
self. Unless you have multiple CPUs in your machine, compile it this way
(actually, I recommend this even if you do have multiple CPUs):
# make no_affinity
# make install ...