linux-kernel - Re: remap_file

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Date:	Mon, 19 May 2014 10:50:22 -0700
From:	Dave Hansen <dave.hansen@...el.com>
To:	Armin Rigo <arigo@...es.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
CC:	Christoph Hellwig <hch@...radead.org>,
	Kenny Simpson <theonetruekenny@...il.com>,
	Michal Hocko <mhocko@...e.cz>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Dave Jones <davej@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: remap_file_pages() use

On 05/19/2014 09:42 AM, Armin Rigo wrote:
> If there is an official way to know in advance how many remappings our
> process is allowed to perform, then we could adapt as the size
> increases.  Or maybe catching ENOMEM and doubling the remapping size
> (in some process-wide synchronization point).  All in all, thanks for
> the note: it looks like there are solutions (even if less elegant than
> remap_file_pages from the user's perspective).

We keep the current count as mm->map_count in the kernel, and the limit
is available because it's a sysctl.  It wouldn't be hard to dump
mm->map_count out in a /proc file somewhere if it would be useful to
you.  Would that work, or is there some other interface that would be
more convenient?
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