[LAD] cpu spikes

[Ralf Mardorf]

On Mon, 8 Feb 2016 21:31:08 +0100, Jeremy Jongepier wrote:
>On 02/08/2016 08:11 PM, Ralf Mardorf wrote:
>> I forgot to mention, the lowlatency is a vanilla kernel with a
>> special configuration, but without a realtime related patch.  
>
>Afaik the Ubuntu low-latency kernel doesn't really have a special
>config, just CONFIG_PREEMPT and CONFIG_HZ_1000.

A comparison between a standard Arch and an Ubuntu lowlatency kernel of
a few other things that come to mind on the fly:

[rocketmouse at archlinux ~]$ uname -r
4.4.1-2-ARCH
[rocketmouse at archlinux ~]$ zgrep THREADING_DEFAULT /proc/config.gz 
[rocketmouse at archlinux ~]$ grep THREADING_DEFAULT /mnt/moonstudio/boot/config-4.2.0-27-lowlatency 
CONFIG_IRQ_FORCED_THREADING_DEFAULT=y
[rocketmouse at archlinux ~]$ zgrep Q_DEFAULT_GOV /proc/config.gz 
# CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE is not set
# CONFIG_CPU_FREQ_DEFAULT_GOV_POWERSAVE is not set
# CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE is not set
CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND=y
# CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE is not set
[rocketmouse at archlinux ~]$ grep -i Q_DEFAULT_GOV /mnt/moonstudio/boot/config-4.2.0-27-lowlatency 
CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE=y
# CONFIG_CPU_FREQ_DEFAULT_GOV_POWERSAVE is not set
# CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE is not set
# CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND is not set
# CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE is not set
[rocketmouse at archlinux ~]$ zgrep NO_HZ /proc/config.gz 
CONFIG_NO_HZ_COMMON=y
CONFIG_NO_HZ_IDLE=y
# CONFIG_NO_HZ_FULL is not set
# CONFIG_NO_HZ is not set
[rocketmouse at archlinux ~]$ grep NO_HZ /mnt/moonstudio/boot/config-4.2.0-27-lowlatency
CONFIG_NO_HZ_COMMON=y
CONFIG_NO_HZ_IDLE=y
# CONFIG_NO_HZ_FULL is not set
CONFIG_NO_HZ=y