linux-kernel - Re: [PATCH 2/2] pid: Optional first-fit pid allocation

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Message-Id: <20250221161854.8ea0dd0b2da05d38574cefc4@linux-foundation.org>
Date: Fri, 21 Feb 2025 16:18:54 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Michal Koutný <mkoutny@...e.com>
Cc: Christian Brauner <brauner@...nel.org>, Alexander Mikhalitsyn
 <alexander@...alicyn.com>, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org, Jonathan Corbet <corbet@....net>, Kees
 Cook <kees@...nel.org>, "Eric W . Biederman" <ebiederm@...ssion.com>, Oleg
 Nesterov <oleg@...hat.com>
Subject: Re: [PATCH 2/2] pid: Optional first-fit pid allocation

On Fri, 21 Feb 2025 18:02:49 +0100 Michal Koutný <mkoutny@...e.com> wrote:

> --- a/Documentation/admin-guide/sysctl/kernel.rst
> +++ b/Documentation/admin-guide/sysctl/kernel.rst
> @@ -1043,6 +1043,8 @@ The last pid allocated in the current (the one task using this sysctl
>  lives in) pid namespace. When selecting a pid for a next task on fork
>  kernel tries to allocate a number starting from this one.
>  
> +When set to -1, first-fit pid numbering is used instead of the next-fit.
> +

This seems thin.  Is there more we can tell our users?  What are the
visible effects of this?  What are the benefits?  Why would they want
to turn it on?

I mean, there are veritable paragraphs in the changelogs, but just a
single line in the user-facing docs.  Seems there could be more...