linux-kernel - Re: [RFC] mm: show message when updating min_free

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Message-ID: <20140108035946.GI4106@localhost.localdomain>
Date:	Wed, 8 Jan 2014 11:59:46 +0800
From:	Han Pingtian <hanpt@...ux.vnet.ibm.com>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	linux-kernel@...r.kernel.org, Dave Hansen <dave.hansen@...el.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org
Subject: Re: [RFC] mm: show message when updating min_free_kbytes in thp

On Mon, Jan 06, 2014 at 05:46:04PM +0100, Michal Hocko wrote:
> On Sun 05-01-14 08:35:01, Han Pingtian wrote:
> [...]
> > From f4d085a880dfae7638b33c242554efb0afc0852b Mon Sep 17 00:00:00 2001
> > From: Han Pingtian <hanpt@...ux.vnet.ibm.com>
> > Date: Fri, 3 Jan 2014 11:10:49 +0800
> > Subject: [PATCH] mm: show message when raising min_free_kbytes in THP
> > 
> > min_free_kbytes may be raised during THP's initialization. Sometimes,
> > this will change the value being set by user. Showing message will
> > clarify this confusion.
> 
> I do not have anything against informing about changing value
> set by user but this will inform also when the default value is
> updated. Is this what you want? Don't you want to check against
> user_min_free_kbytes? (0 if not set by user)
> 
But looks like the user can set min_free_kbytes to 0 by

    echo 0 > /proc/sys/vm/min_free_kbytes

and even set it to -1 the same way. So I think we need to restrict the
value of min_free_kbytes > 0 first?

> Btw. Do we want to restore the original value when khugepaged is
> disabled?
> 

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