Re: [PATCH 2/2] mm: replace remap_file_pages() syscall with emulation

From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>
Cc: Sasha Levin <sasha.levin@oracle.com>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	peterz@infradead.org, mingo@kernel.org
Subject: Re: [PATCH 2/2] mm: replace remap_file_pages() syscall with emulation
Date: Thu, 15 May 2014 00:17:48 +0300	[thread overview]
Message-ID: <20140514211748.GA15970@node.dhcp.inet.fi> (raw)
In-Reply-To: <5373D781.7020109@oracle.com>

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