18 Chapter 3. Configuration
3.4. Starting TUX
TUX can be started by issuing the command /etc/rc.d/init.d/tux start.
This script is written to start TUX on a single-processor as well as a multi-processor server.
If youchoose towrite yourown scriptto startTUX orstart itfromthe/usr/sbin/tux binary,
you can use the following options:
Table 3-3. /usr/sbin/tux options
Option Description
-t, --threads=N number of tux threads
-d, --docroot=path directory path for document root
-m, --modpath=path directory path for user-space loadable TUX modules
-d, --daemon run in the background as a daemon
-D, --date-interval=seconds how often (in seconds) to update the date string, the
default is 1 second
-?, --help show help message
--usage display brief usage message
IRQ affinity is a small performance boost. If you are not experiencing any performance difficulties,
it is not recommended you try the following.
3.4.1. IRQ Affinity
Binding IRQ’s to a group of CPU’s is a new feature of the 2.4 kernel. While it was originally
developed as part of TUX, it is now a generic and independent kernel feature. Every
IRQ source in Linux has an entry in /proc/irq directory. For example, the settings for
IRQ 40 is stored in /proc/irq/40. IRQ affinity, or IRQ bindings, is configured though
the smp_affinity setting in that directory. For example, the smp_affinity for IRQ 40 is in
/proc/irq/40/smp_affinity. The value of the smp_affinity setting is a bitmask of all
CPU’s that are permitted as a resource for the given IRQ. The default value for smp_affinity
is the HEX value 0xffffffff. This means the processes for the IRQ are sent to all CPU’s.
You are not allowed to turn off all CPU’s for an IRQ. If the IRQ controller does not support
IRQ affinity, the value can not be changed from the default. If multiple CPU’s are defined,
then the IRQ source uses the least busy CPU. This is called ’lowest priority APIC routing.’
IRQ affinity is achieved by binding an IRQ to a specific CPU or group of CPU’s by echoing
a HEX value to smp_affinity for the IRQ.
Thus, TUX thread N is bound to CPU N. If a single TUX thread is used (which is recom-
mended) andthere is only onenetwork interface card, thenthe network interface card’s IRQ
should be bound to CPU0.
