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

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Message-Id: <20180213171432.13c496c6603255bff66ce826@linux-foundation.org>
Date:   Tue, 13 Feb 2018 17:14:32 -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 Tue, 13 Feb 2018 15:55:11 -0800 (PST) David Rientjes <rientjes@...gle.com> wrote:

> > 
> > 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.
> > 
> 
> They still have the (current) ability to define the exact amount of bytes 
> down to page sized granularity, whereas 1% would yield 40GB on a 4TB 
> system.  I'm not sure that people will want any finer-grained control if 
> defining the proportion of the system for kernelcore.  They do have the 
> ability with the existing interface, though, if they want to be that 
> precise.
> 
> (This is a cop out for not implementing some fractional percentage parser, 
>  although that would be possible as a more complete solution.)

And the interface which you've proposed can be seamlessly extended to
accept 0.07%, so not a problem.