APPLIED[M:linux-lowlatency/proxy]: [PATCH][M:lowlatency] UBUNTU: [Config] lowlatency: enhance desktop responsiveness

[Stefan Bader]

On 06.06.23 10:02, Andrea Righi wrote:
> BugLink: https://bugs.launchpad.net/bugs/2023007
> 
> Enable the following kernel configs to make the lowlatency kernel more
> suitable for a desktop-oriented context and give access to additional
> run-time / boot-time user-space settings:
> 
>   - CONFIG_NO_HZ_FULL=y: enable access to "Full tickless mode" (shutdown
>     clock tick when possible across all the enabled CPUs if they are
>     either idle or running 1 task - reduce kernel jitter of running tasks
>     due to the periodic clock tick, must be enabled at boot time passing
>     `nohz_full=<cpu_list>`)
> 
>   - CONFIG_RCU_NOCB_CPU=y, CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y: move RCU
>     callbacks from softirq context to kthread context (reduce time spent
>     in softirqs with preemption disabled to improve the overall system
>     responsiveness, at the cost of introducing a potential performance
>     penalty, because RCU callbacks are now processed by kernel threads)
> 
>   - CONFIG_RCU_LAZY=y: batch RCU callbacks and then flush them after a
>     timed delay instead of executing them immediately (can provide 5~10%
>     power-savings for idle or lightly-loaded systems, this is extremely
>     useful for laptops / portable devices [1])
> 
> [1] https://lore.kernel.org/lkml/20221016162305.2489629-3-joel@joelfernandes.org/
> 
> Signed-off-by: Andrea Righi <andrea.righi at canonical.com>
> ---

Applied to This was already applied to mantic:linux-lowlatency. Thanks.

-Stefan

>   debian.lowlatency/config/annotations | 24 ++++++++++++++++++++++--
>   1 file changed, 22 insertions(+), 2 deletions(-)
> 
> diff --git a/debian.lowlatency/config/annotations b/debian.lowlatency/config/annotations
> index fef2202364bc..737a55be4ae2 100644
> --- a/debian.lowlatency/config/annotations
> +++ b/debian.lowlatency/config/annotations
> @@ -15,15 +15,35 @@ CONFIG_HZ_250                                   note<'Override default HZ used i
>   CONFIG_LATENCYTOP                               policy<{'amd64': 'y', 'arm64': 'y'}>
>   CONFIG_LATENCYTOP                               note<'https://lists.ubuntu.com/archives/kernel-team/2014-July/045006.html, LP#1655986'>
>   
> +CONFIG_NO_HZ_FULL                               policy<{'amd64': 'y', 'arm64': 'y'}>
> +CONFIG_NO_HZ_FULL                               note<'Enable access to "Full tickless mode" (LP: #2023007)'>
> +
> +CONFIG_NO_HZ_IDLE                               policy<{'amd64': 'n', 'arm64': 'n'}>
> +CONFIG_NO_HZ_IDLE                               note<'Disabled in favor of CONFIG_NO_HZ_FULL (LP: #2023007)'>
> +
>   CONFIG_PREEMPT                                  policy<{'amd64': 'y', 'arm64': 'y'}>
> -CONFIG_PREEMPT                                  note<'Enable fully preemptible kernel'>
> +CONFIG_PREEMPT                                  note<'Enable fully preemptible kernel by default (can be changed at runtime via /sys/kernel/debug/sched/preempt)'>
>   
>   CONFIG_PREEMPT_VOLUNTARY                        policy<{'amd64': 'n', 'arm64': 'n'}>
> -CONFIG_PREEMPT_VOLUNTARY                        note<'Disable voluntary preemption model'>
> +CONFIG_PREEMPT_VOLUNTARY                        note<'Disable voluntary preemption model by default (can be changed at runtime via /sys/kernel/debug/sched/preempt)'>
> +
> +CONFIG_RCU_LAZY                                 policy<{'amd64': 'y', 'arm64': 'y'}>
> +CONFIG_RCU_LAZY                                 note<'Batch RCU callbacks and then flush them after a timed delay instead of executing them immediately (LP: #2023007)'>
> +
> +CONFIG_RCU_NOCB_CPU                             policy<{'amd64': 'y', 'arm64': 'y'}>
> +CONFIG_RCU_NOCB_CPU                             note<'Move RCU callbacks from softirq context to kthread context (LP: #2023007)'>
> +
> +CONFIG_RCU_NOCB_CPU_DEFAULT_ALL                 policy<{'amd64': 'y', 'arm64': 'y'}>
> +CONFIG_RCU_NOCB_CPU_DEFAULT_ALL                 note<'Enable CONFIG_RCU_NOCB_CPU across all CPUs by default (LP: #2023007)'>
>   
>   
>   # ---- Annotations without notes ----
>   
>   CONFIG_CC_VERSION_TEXT                          policy<{'amd64': '"x86_64-linux-gnu-gcc-12 (Ubuntu 12.3.0-1ubuntu1) 12.3.0"', 'arm64': '"aarch64-linux-gnu-gcc-12 (Ubuntu 12.3.0-1ubuntu1) 12.3.0"'}>
> +CONFIG_CONTEXT_TRACKING_USER                    policy<{'amd64': 'y', 'arm64': 'y'}>
> +CONFIG_CONTEXT_TRACKING_USER_FORCE              policy<{'amd64': 'n', 'arm64': 'n'}>
>   CONFIG_GCC_VERSION                              policy<{'amd64': '120300', 'arm64': '120300'}>
>   CONFIG_HZ                                       policy<{'amd64': '1000', 'arm64': '1000'}>
> +CONFIG_TICK_CPU_ACCOUNTING                      policy<{'amd64': '-', 'arm64': '-'}>
> +CONFIG_VIRT_CPU_ACCOUNTING                      policy<{'amd64': 'y', 'arm64': 'y'}>
> +CONFIG_VIRT_CPU_ACCOUNTING_GEN                  policy<{'amd64': 'y', 'arm64': 'y'}>

-- 
- Stefan

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