Re: [PATCH] mm: introduce MADV_CLR_HUGEPAGE

From: Mike Rapoprt <rppt@linux.vnet.ibm.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>,
	"Kirill A. Shutemov" <kirill@shutemov.name>,
	Andrew Morton <akpm@linux-foundation.org>,
	Arnd Bergmann <arnd@arndb.de>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Pavel Emelyanov <xemul@virtuozzo.com>,
	linux-mm <linux-mm@kvack.org>,
	lkml <linux-kernel@vger.kernel.org>,
	Linux API <linux-api@vger.kernel.org>
Subject: Re: [PATCH] mm: introduce MADV_CLR_HUGEPAGE
Date: Wed, 31 May 2017 15:25:43 +0300	[thread overview]
Message-ID: <D593CAD3-C8AB-479F-970C-AF67F00CEF3A@linux.vnet.ibm.com> (raw)
In-Reply-To: <20170531120533.GK27783@dhcp22.suse.cz>

On May 31, 2017 3:05:56 PM GMT+03:00, Michal Hocko <mhocko@kernel.org> wrote:
>On Wed 31-05-17 12:08:45, Mike Rapoport wrote:
>> On Tue, May 30, 2017 at 12:39:30PM +0200, Michal Hocko wrote:
>[...]
>> > Also do you expect somebody else would use new madvise? What would
>be the
>> > usecase?
>> 
>> I can think of an application that wants to keep 4K pages to save
>physical
>> memory for certain phase, e.g. until these pages are populated with
>very
>> few data. After the memory usage increases, the application may wish
>to
>> stop preventing khugepged from merging these pages, but it does not
>have
>> strong inclination to force use of huge pages.
>
>Well, is actually anybody going to do that?

Well, I don't know, it's pretty much future telling :)
For sure, without the new madvise nobody will be even able to do that.

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