linux-kernel - Re: remap_file

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Message-Id: <20140519143540.BE9F6E009B@blue.fi.intel.com>
Date:	Mon, 19 May 2014 17:35:40 +0300 (EEST)
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Kenny Simpson <theonetruekenny@...il.com>
Cc:	Michal Hocko <mhocko@...e.cz>, linux-kernel@...r.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Dave Jones <davej@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Armin Rigo <arigo@...es.org>
Subject: Re: remap_file_pages() use

Michal Hocko wrote:
> [CCing Kirill and other people involved]
> 
> On Sun 18-05-14 00:03:28, Kenny Simpson wrote:
> > I saw that remap_file_pages() was possibly going away to be replaced
> > by some emulation. I've used this call in several projects over the
> > years mostly as a way of mapping multiple virtual memory pages to
> > alias the same private or shared memory region (to do things like
> > circular buffers). mmap()
> > in the case of anonymous memory doesn't work as well since there is
> > not a file descriptor to reference.
> > 
> > Would this sort of thing be supported in the emulation, or should I be
> > planning on reimplementing/rewriting some things?

>From functional POV, emulation *should* be identical to original
remap_file_pages(), but slower. It would be nice, if you test it early.

It's not clear yet how long emulation will be there.
Is there a reason why you can't use fd from shared memory (shm_open() or
direct open() on /dev/shm/xxx)?

-- 
 Kirill A. Shutemov
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