linux-kernel - Re: [PATCH] docs/vm: clarify overcommit amount sysctl behavior

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Date:   Sat, 11 Dec 2021 22:21:42 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Anssi Hannula <anssi.hannula@....fi>
Cc:     Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] docs/vm: clarify overcommit amount sysctl behavior

On Sat, Dec 11, 2021 at 09:41:59PM +0200, Anssi Hannula wrote:
> Documentation/vm/overcommit-accounting.rst says that the overcommit
> amount can be set via vm.overcommit_ratio and vm.overcommit_kbytes.
> 
> Add a clarification that those only take effect in overcommit handling
> mode 2 ("Don't overcommit"), i.e. they do not act as an "additional"
> limit that is always enforced.
> 
> Signed-off-by: Anssi Hannula <anssi.hannula@....fi>
> ---

Simple and clear improvement, IMO.  Cc'ing linux-mm to get more eyes on
it.

> I've had to look this one up in the code enough times already :)
> 
> 
>  Documentation/vm/overcommit-accounting.rst | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/vm/overcommit-accounting.rst b/Documentation/vm/overcommit-accounting.rst
> index 0dd54bbe4afa..1addb0c374a4 100644
> --- a/Documentation/vm/overcommit-accounting.rst
> +++ b/Documentation/vm/overcommit-accounting.rst
> @@ -34,7 +34,8 @@ The Linux kernel supports the following overcommit handling modes
>  The overcommit policy is set via the sysctl ``vm.overcommit_memory``.
>  
>  The overcommit amount can be set via ``vm.overcommit_ratio`` (percentage)
> -or ``vm.overcommit_kbytes`` (absolute value).
> +or ``vm.overcommit_kbytes`` (absolute value). These only have an effect
> +when ``vm.overcommit_memory`` is set to 2.
>  
>  The current overcommit limit and amount committed are viewable in
>  ``/proc/meminfo`` as CommitLimit and Committed_AS respectively.
> -- 
> 2.31.1
>