System information

148 System Analysis and Tuning Guide
cd /sys/devices/system/cpu/cpu0/cpufreq/conservative/
2 Show the current value of ignore_nice_load with:
cat ignore_nice_load
3 To set the value to 1, execute:
echo 1 > ignore_nice_load
TIP: Using the Same Value for All Cores
When setting the ignore_nice_load value for cpu0, the same value is
automatically used for all cores. In this case, you do not need to repeat the
steps above for each of the processors where you want to modify this gover-
nor parameter.
Another parameter that significantly impacts the performance loss caused by dynam-
ic frequency scaling is the sampling rate (rate at which the governor checks the cur-
rent CPU load and adjusts the processor's frequency accordingly). Its default value
depends on a BIOS value and it should be as low as possible. However, in modern sys-
tems, an appropriate sampling rate is set by default and does not need manual inter-
vention.
11.4.2 Tuning Options for C-states
By default, SUSE Linux Enterprise Server uses C-states appropriate-
ly. The only parameter you might want to touch for optimization is the
sched_mc_power_savings scheduler. Instead of distributing a work load across
all cores with the effect that all cores are used only at a minimum level, the kernel can
try to schedule processes on as few cores as possible so that the others can go idle.
This helps to save power as it allows some processors to be idle for a longer time so
they can reach a higher C-state. However, the actual savings depend on a number of
factors, for example how many processors are available and which C-states are sup-
ported by them (especially deeper ones such as C3 to C6).
If sched_mc_power_savings is set to 0 (default value), no special scheduling is
done. If it is set to 1, the scheduler tries to consolidate the work onto the fewest num-
ber of processors possible in the case that all processors are a little busy. To modify
this parameter, proceed as follows: