lkml.org 
[lkml]   [2018]   [Feb]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 6/6] sched/isolation: Tick offload documentation

* Frederic Weisbecker <frederic@kernel.org> wrote:

> Update the documentation to reflect the 1Hz tick offload changes.
>
> Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
> Cc: Chris Metcalf <cmetcalf@mellanox.com>
> Cc: Christoph Lameter <cl@linux.com>
> Cc: Luiz Capitulino <lcapitulino@redhat.com>
> Cc: Mike Galbraith <efault@gmx.de>
> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Rik van Riel <riel@redhat.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Wanpeng Li <kernellwp@gmail.com>
> Cc: Ingo Molnar <mingo@kernel.org>
> ---
> Documentation/admin-guide/kernel-parameters.txt | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 39ac9d4..c851e41 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1762,7 +1762,11 @@
> specified in the flag list (default: domain):
>
> nohz
> - Disable the tick when a single task runs.
> + Disable the tick when a single task runs. A residual 1Hz
> + tick is offloaded to workqueues that you need to affine
> + to housekeeping through the sysfs file
> + /sys/devices/virtual/workqueue/cpumask or using the below
> + domain flag.

This is pretty ambiguous and somewhat confusing, I'd suggest something like:

nohz
Disable the tick when a single task runs.

A residual 1Hz tick is offloaded to workqueues, which you
need to affine to housekeeping through the global
workqueue's affinity configured via the
/sys/devices/virtual/workqueue/cpumask sysfs file, or
by using the 'domain' flag described below.

NOTE: by default the global workqueue runs on all CPUs,
so to protect individual CPUs the 'cpumask' file has to
be configured manually after bootup.

Assuming what I wrote is correct - the CPU isolation config space is pretty
confusing all around and should be made a lot more human friendly ...

Thanks,

Ingo

\
 
 \ /
  Last update: 2018-02-09 08:07    [W:0.072 / U:15.772 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site