linux-kernel - Re: [patch 1/2] mm, page_alloc: extend kernelcore and movablecore for percent

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Message-Id: <20180213154607.f631e2e033f42c32925e3d2d@linux-foundation.org>
Date:   Tue, 13 Feb 2018 15:46:07 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Jonathan Corbet <corbet@....net>, Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...e.de>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-doc@...r.kernel.org
Subject: Re: [patch 1/2] mm, page_alloc: extend kernelcore and movablecore
 for percent

On Mon, 12 Feb 2018 16:24:25 -0800 (PST) David Rientjes <rientjes@...gle.com> wrote:

> Both kernelcore= and movablecore= can be used to define the amount of
> ZONE_NORMAL and ZONE_MOVABLE on a system, respectively.  This requires
> the system memory capacity to be known when specifying the command line,
> however.
> 
> This introduces the ability to define both kernelcore= and movablecore=
> as a percentage of total system memory.  This is convenient for systems
> software that wants to define the amount of ZONE_MOVABLE, for example, as
> a proportion of a system's memory rather than a hardcoded byte value.
> 
> To define the percentage, the final character of the parameter should be
> a '%'.

Is this fine-grained enough?  We've had percentage-based tunables in
the past, and 10 years later when systems are vastly larger, 1% is too
much.