linux-kernel - Re: [PATCH 2/2] mm: replace remap_file

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Date:	Thu, 15 May 2014 00:17:48 +0300
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Sasha Levin <sasha.levin@...cle.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	peterz@...radead.org, mingo@...nel.org
Subject: Re: [PATCH 2/2] mm: replace remap_file_pages() syscall with emulation

On Wed, May 14, 2014 at 04:52:17PM -0400, Sasha Levin wrote:
> On 05/12/2014 01:05 PM, Kirill A. Shutemov wrote:
> > Taking into account your employment, is it possible to check how the RDBMS
> > (old but it still supported 32-bit versions) would react on -ENOSYS here?
> 
> Alrighty, I got an answer:
> 
> 1. remap_file_pages() only works when the "VLM" feature of the db is enabled,
> so those databases can work just fine without it, but be limited to 3-4GB of
> memory. This is not needed at all on 64bit machines.

Okay. And it seems user need to enable it manually with option
USE_INDIRECT_DATA_BUFFERS=TRUE.

http://docs.oracle.com/cd/B28359_01/server.111/b32009/appi_vlm.htm

> 2. As of OL7 (kernel 3.8), there will not be a 32bit kernel build. I'm still
> waiting for an answer whether there will do a 32bit DB build for a 64bit kernel,
> but that never happened before and seems unlikely.
> 
> 3. They're basically saying that by the time upstream releases a kernel without
> remap_file_pages() no one will need it here.
> 
> To sum it up, they're fine with removing remap_file_pages().

Andrew, Linus, what will we do here: live with emulation or just kill the
syscall? Or may be kill the syscall after few releases with emulation?

-- 
 Kirill A. Shutemov
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