Linux Desktop Hacks

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 ...