linux-kernel - Re: [PATCH] mm: introduce MADV_CLR

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Message-Id: <D593CAD3-C8AB-479F-970C-AF67F00CEF3A@linux.vnet.ibm.com>
Date:   Wed, 31 May 2017 15:25:43 +0300
From:   Mike Rapoprt <rppt@...ux.vnet.ibm.com>
To:     Michal Hocko <mhocko@...nel.org>
CC:     Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Pavel Emelyanov <xemul@...tuozzo.com>,
        linux-mm <linux-mm@...ck.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH] mm: introduce MADV_CLR_HUGEPAGE



On May 31, 2017 3:05:56 PM GMT+03:00, Michal Hocko <mhocko@...nel.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.