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Kernel Testing

Building your own kernel

A short description of how to build a kernel for testing.

linux-lowlatency

Shipped with Ubuntu Studio since 12.04 Precise. Principally a standard Ubuntu kernel (no additional patches to the code, allthough the linux-lowlatency shipped with precise includes a minor patch).

Configurations of interest for linux-lowlatency

These configs need to be somewhat documented and tested

To enable low latency (needs to be expanded)

• CONFIG_PREEMPT

  • conflicts with: CONFIG_PREEMPT_NONE

  • conflicts with: CONFIG_PREEMPT_VOLUNTARY

To enable this option edit the config file to have these line read:

CONFIG_PREEMPT=y
# CONFIG_PREEMPT_NONE
# CONFIG_PREEMPT_VOLUNTARY

May reduce latency

• CONFIG_PREEMPT_RCU

CONFIG_PREEMPT_RCU=y

additional, related configs

• CONFIG_TREE_PREEMPT_RCU

• CONFIG_RCU_BOOST

• CONFIG_RCU_CPU_STALL_DETECTOR

• CONFIG_RCU_CPU_STALL_VERBOSE

as configure in current -lowlatency..

CONFIG_TREE_PREEMPT_RCU=y
# CONFIG_RCU_BOOST is not set
# CONFIG_RCU_CPU_STALL_DETECTOR is not set
# CONFIG_RCU_CPU_STALL_VERBOSE is not set

To enable the use of the rtirq script to change rtprio for devices:

this enables the use of threadirqs as a kernel boot parameter

• CONFIG_IRQ_FORCED_THREADING

optionally, to make threadirqs a default boot parameter

• CONFIG_CMDLINE

  • depends on: CONFIG_CMDLINE_BOOL

To enable these options edit the config file to have these line read:

IRQ_FORCED_THREADING=y
CONFIG_CMDLINE="threadirqs"
CONFIG_CMDLINE_BOOL=y

High resolution timer:

(Not exactly sure which of CONFIG_HZ=1000 and CONFIG_HZ_1000=y depend on which. )

• CONFIG_HZ_1000

• CONFIG_HZ

  • depends on: CONFIG_NO_HZ

to enable high resolution timer

CONFIG_HZ_1000=y
CONFIG_HZ=1000
# CONFIG_NO_HZ is not set

(optionally, tickless timer - add the config here)

Need to be investigated

• CONFIG_NTP_PPS

• CONFIG_SLAB

• CONFIG_PREEMPT_NOTIFIERS

• CONFIG_EXPERT

• CONFIG_PREEMPT_TRACER

• CONFIG_DEBUG_KERNEL

as used in current -lowlatency

# CONFIG_NTP_PPS is not set
CONFIG_SLAB=y
CONFIG_PREEMPT_NOTIFIERS=y
# CONFIG_EXPERT is not set
# CONFIG_PREEMPT_TRACER is not set
# CONFIG_DEBUG_KERNEL is not set 

Additional configs

* CONFIG_RT_GROUP_SCHED

linux-rt

Not in Ubuntu repo since 9.10 Karmic.