From: Mel Gorman <mel@csn.ul.ie>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Petr Holasek <pholasek@redhat.com>,
linux-kernel@vger.kernel.org, Andi Kleen <ak@linux.intel.com>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
Wu Fengguang <fengguang.wu@intel.com>,
linux-mm@kvack.org
Subject: Re: [PATCH] hugetlbfs: correct handling of negative input to /proc/sys/vm/nr_hugepages
Date: Thu, 24 Feb 2011 09:49:12 +0000 [thread overview]
Message-ID: <20110224094912.GO15652@csn.ul.ie> (raw)
In-Reply-To: <20110223161818.9876cc10.akpm@linux-foundation.org>
On Wed, Feb 23, 2011 at 04:18:18PM -0800, Andrew Morton wrote:
> On Tue, 22 Feb 2011 10:02:36 +0000
> Mel Gorman <mel@csn.ul.ie> wrote:
>
> > On Mon, Feb 21, 2011 at 04:47:49PM +0100, Petr Holasek wrote:
> > > When user insert negative value into /proc/sys/vm/nr_hugepages it will result
> > > in the setting a random number of HugePages in system (can be easily showed
> > > at /proc/meminfo output).
> >
> > I bet you a shiny penny that the value of HugePages becomes the maximum
> > number that could be allocated by the system at the time rather than a
> > random value.
>
> That seems to be the case from my reading. In which case the patch
> removes probably-undocumented and possibly-useful existing behavior.
>
It's not proof that no one does this but I'm not aware of any documentation
related to hugetlbfs that recommends writing negative values to take advantage
of this side-effect. It's more likely they simply wrote a very large number
to nr_hugepages if they wanted "as many hugepages as possible" as it makes
more intuitive sense than asking for a negative amount of pages. hugeadm at
least is not depending on this behaviour AFAIK.
--
Mel Gorman
SUSE Labs
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next prev parent reply other threads:[~2011-02-24 9:49 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-21 15:47 Petr Holasek
2011-02-22 0:30 ` Naoya Horiguchi
2011-02-22 10:02 ` Mel Gorman
2011-02-24 0:18 ` Andrew Morton
2011-02-24 9:49 ` Mel Gorman [this message]
2011-02-24 18:20 ` Eric B Munson
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