Subject: Re: [PATCH 33/33] doc: Add housekeeping documentation

From: Frederic Weisbecker <[email-masked]>
Date: Wed, 31 Dec 2025 16:25:49 +0100

Le Fri, Dec 26, 2025 at 07:39:28PM -0500, Waiman Long a écrit :
> On 12/24/25 8:45 AM, Frederic Weisbecker wrote:
> > Signed-off-by: Frederic Weisbecker <[email-masked]>
> > ---
> >   Documentation/core-api/housekeeping.rst | 111 ++++++++++++++++++++++++
> >   Documentation/core-api/index.rst        |   1 +
> >   2 files changed, 112 insertions(+)
> >   create mode 100644 Documentation/core-api/housekeeping.rst
> > 
> > diff --git a/Documentation/core-api/housekeeping.rst b/Documentation/core-api/housekeeping.rst
> > new file mode 100644
> > index 000000000000..e5417302774c
> > --- /dev/null
> > +++ b/Documentation/core-api/housekeeping.rst
> > @@ -0,0 +1,111 @@
> > +======================================
> > +Housekeeping
> > +======================================
> > +
> > +
> > +CPU Isolation moves away kernel work that may otherwise run on any CPU.
> > +The purpose of its related features is to reduce the OS jitter that some
> > +extreme workloads can't stand, such as in some DPDK usecases.
> Nit: "usecases" => "use cases"

Are you sure? I'm not a native speaker but at least the kernel
has established its use:

$ git grep usecase | wc -l
517

> > +
> > +The kernel work moved away by CPU isolation is commonly described as
> > +"housekeeping" because it includes ground work that performs cleanups,
> > +statistics maintainance and actions relying on them, memory release,
> > +various deferrals etc...
> > +
> > +Sometimes housekeeping is just some unbound work (unbound workqueues,
> > +unbound timers, ...) that gets easily assigned to non-isolated CPUs.
> > +But sometimes housekeeping is tied to a specific CPU and requires
> > +elaborated tricks to be offloaded to non-isolated CPUs (RCU_NOCB, remote
> > +scheduler tick, etc...).
> > +
> > +Thus, a housekeeping CPU can be considered as the reverse of an isolated
> > +CPU. It is simply a CPU that can execute housekeeping work. There must
> > +always be at least one online housekeeping CPU at any time. The CPUs that
> > +are not	isolated are automatically assigned as housekeeping.
> Nit: extra white spaces between "not" and "isolated".

Somehow it has disappeared in my tree, some Brunaidh must have fixed
that while I was sleeping. That's nice!

> > diff --git a/Documentation/core-api/index.rst b/Documentation/core-api/index.rst
> > index 5eb0fbbbc323..79fe7735692e 100644
> > --- a/Documentation/core-api/index.rst
> > +++ b/Documentation/core-api/index.rst
> > @@ -25,6 +25,7 @@ it.
> >      symbol-namespaces
> >      asm-annotations
> >      real-time/index
> > +   housekeeping.rst
> >   Data structures and low-level utilities
> >   =======================================
> Acked-by: Waiman Long <[email-masked]>

Thanks! 

-- 
Frederic Weisbecker
SUSE Labs