linux-kernel - Re: [PATCH RESEND 1/3] docs: cgroup: Explain reclaim protection target

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Message-ID: <87wm3xwtcm.fsf@trenco.lwn.net>
Date: Mon, 10 Nov 2025 13:00:41 -0700
From: Jonathan Corbet <corbet@....net>
To: Michal Koutný <mkoutny@...e.com>,
 cgroups@...r.kernel.org,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: Natalie Vock <natalie.vock@....de>, Maarten Lankhorst
 <dev@...khorst.se>, Michal Koutný <mkoutny@...e.com>,
 Tejun Heo
 <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH RESEND 1/3] docs: cgroup: Explain reclaim protection target

Michal Koutný <mkoutny@...e.com> writes:

> The protection target is necessary to understand how effective reclaim
> protection applies in the hierarchy.
>
> Signed-off-by: Michal Koutný <mkoutny@...e.com>
> ---
>  Documentation/admin-guide/cgroup-v2.rst | 24 +++++++++++++++++++++---
>  1 file changed, 21 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
> index 0e6c67ac585a0..a6def773a3072 100644
> --- a/Documentation/admin-guide/cgroup-v2.rst
> +++ b/Documentation/admin-guide/cgroup-v2.rst
> @@ -53,7 +53,8 @@ v1 is available under :ref:`Documentation/admin-guide/cgroup-v1/index.rst <cgrou
>       5-2. Memory
>         5-2-1. Memory Interface Files
>         5-2-2. Usage Guidelines
> -       5-2-3. Memory Ownership
> +       5-2-3. Reclaim Protection
> +       5-2-4. Memory Ownership

I always have to ask...do we really need the manually maintained TOC
here? 

>       5-3. IO
>         5-3-1. IO Interface Files
>         5-3-2. Writeback
> @@ -1317,7 +1318,7 @@ PAGE_SIZE multiple when read back.
>  	smaller overages.
>  
>  	Effective min boundary is limited by memory.min values of
> -	all ancestor cgroups. If there is memory.min overcommitment
> +	ancestor cgroups. If there is memory.min overcommitment
>  	(child cgroup or cgroups are requiring more protected memory
>  	than parent will allow), then each child cgroup will get
>  	the part of parent's protection proportional to its
> @@ -1343,7 +1344,7 @@ PAGE_SIZE multiple when read back.
>  	smaller overages.
>  
>  	Effective low boundary is limited by memory.low values of
> -	all ancestor cgroups. If there is memory.low overcommitment
> +	ancestor cgroups. If there is memory.low overcommitment
>  	(child cgroup or cgroups are requiring more protected memory
>  	than parent will allow), then each child cgroup will get
>  	the part of parent's protection proportional to its
> @@ -1934,6 +1935,23 @@ memory - is necessary to determine whether a workload needs more
>  memory; unfortunately, memory pressure monitoring mechanism isn't
>  implemented yet.
>  
> +Reclaim Protection
> +~~~~~~~~~~~~~~~~~~
> +
> +The protection configured with "memory.low" or "memory.min" applies relatively
> +to the target of the reclaim (i.e. any of memory cgroup limits, proactive
> +memory.reclaim or global reclaim apparently located in the root cgroup).
> +
> +  root ... - A - B - C
> +              \    ` D
> +               ` E

This will not render properly, you want it in a literal block.  The
easiest way is to just make the line above read:

   ...located in the root cgroup)::

Thanks,

jon