linux-kernel - Re: [PATCH V3 3/5] mm: mlock: Introduce VM_LOCKONFAULT and add mlock flags to enable it

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Message-ID: <20150710101118.5d04d627@lwn.net>
Date:	Fri, 10 Jul 2015 10:11:18 -0600
From:	Jonathan Corbet <corbet@....net>
To:	Eric B Munson <emunson@...mai.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.cz>,
	Vlastimil Babka <vbabka@...e.cz>, linux-alpha@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mips@...ux-mips.org,
	linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	sparclinux@...r.kernel.org, linux-xtensa@...ux-xtensa.org,
	linux-mm@...ck.org, linux-arch@...r.kernel.org,
	linux-api@...r.kernel.org
Subject: Re: [PATCH V3 3/5] mm: mlock: Introduce VM_LOCKONFAULT and add
 mlock flags to enable it

On Thu, 9 Jul 2015 14:46:35 -0400
Eric B Munson <emunson@...mai.com> wrote:

> > One other question...if I call mlock2(MLOCK_ONFAULT) on a range that
> > already has resident pages, I believe that those pages will not be locked
> > until they are reclaimed and faulted back in again, right?  I suspect that
> > could be surprising to users.  
> 
> That is the case.  I am looking into what it would take to find only the
> present pages in a range and lock them, if that is the behavior that is
> preferred I can include it in the updated series.

For whatever my $0.02 is worth, I think that should be done.  Otherwise
the mlock2() interface is essentially nondeterministic; you'll never
really know if a specific page is locked or not.

Thanks,

jon
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