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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Quchaosheng <quchaosheng000406@163.com>
Cc: Jonathan Corbet <corbet@lwn.net>,
	Shuah Khan <skhan@linuxfoundation.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/2] sched/doc: add a preemption model overview
Message-ID: <20260923072825._dV0YtYP@linutronix.de>
References: <20260922083101.99685-1-quchaosheng000406@163.com>
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In-Reply-To: <20260922083101.99685-1-quchaosheng000406@163.com>

On 2026-09-22 16:31:00 [+0800], Quchaosheng wrote:
> The scheduler documentation describes the individual scheduling classes
> and various tuning knobs, but there is nothing that describes the
> preemption models themselves.  The only place where they are documented
> is the kernel-parameters entry for "preempt=3D", which explains the boot
> time parameter but not the models it selects.
=E2=80=A6
> Assisted-by: LLM
> Suggested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> Signed-off-by: Quchaosheng <quchaosheng000406@163.com>

This reads very nice.
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Once comment bellow.

=E2=80=A6
> --- /dev/null
> +++ b/Documentation/scheduler/sched-preemption.rst
> @@ -0,0 +1,84 @@
=E2=80=A6
> +separates the models:
> +
> +``none``
> +	Code paths with long loops contain explicit ``cond_resched()`` calls,
> +	which perform the scheduling.
> +
> +``voluntary``
> +	As ``none``, and functions which are known to be able to block gain
> +	such a call as well.

I know what you are trying to say but it does not sound obvious that you
refer here to cond_resched(). At least to me.

> +
> +``full``
> +	Explicit preemption points are no longer involved.  The kernel tracks
> +	whether it may be preempted and schedules once the request can be
> +	honoured.
=E2=80=A6

Sebastian