From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f42.google.com (mail-pa0-f42.google.com [209.85.220.42]) by kanga.kvack.org (Postfix) with ESMTP id 77CCB6B0035 for ; Wed, 7 May 2014 12:45:11 -0400 (EDT) Received: by mail-pa0-f42.google.com with SMTP id rd3so1420378pab.1 for ; Wed, 07 May 2014 09:45:11 -0700 (PDT) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTP id vw5si14148756pab.5.2014.05.07.09.45.10 for ; Wed, 07 May 2014 09:45:10 -0700 (PDT) Date: Wed, 7 May 2014 09:46:01 -0700 From: Andrew Morton Subject: Re: [RFC, PATCH 0/8] remap_file_pages() decommission Message-Id: <20140507094601.0f7fd266.akpm@linux-foundation.org> In-Reply-To: <20140507091258.GP11096@twins.programming.kicks-ass.net> References: <1399387052-31660-1-git-send-email-kirill.shutemov@linux.intel.com> <20140506143542.1d4e5f41be58b3ad3543ffe3@linux-foundation.org> <20140506230323.GA14821@node.dhcp.inet.fi> <20140506162856.2a94db336b91db5525ed0457@linux-foundation.org> <20140507091258.GP11096@twins.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Peter Zijlstra Cc: "Kirill A. Shutemov" , Linus Torvalds , "Kirill A. Shutemov" , linux-mm , Ingo Molnar On Wed, 7 May 2014 11:12:58 +0200 Peter Zijlstra wrote: > On Tue, May 06, 2014 at 04:28:56PM -0700, Andrew Morton wrote: > > On Wed, 7 May 2014 02:03:23 +0300 "Kirill A. Shutemov" wrote: > > > > > remap_file_pages(2) was invented to be able efficiently map parts of > > > huge file into limited 32-bit virtual address space such as in database > > > workloads. > > > > > > Nonlinear mappings are pain to support and it seems there's no > > > legitimate use-cases nowadays since 64-bit systems are widely available. > > > > > > Let's deprecate remap_file_pages() syscall in hope to get rid of code > > > one day. > > > > Before we do this we should ensure that your proposed replacement is viable > > and desirable. If we later decide not to proceed with it, this patch will > > sow confusion. > > Chicken meet Egg ? > > How are we supposed to test if its viable if we have no known users? Same way we always do - finish the code, developer test, review, give it a spin in linux-next, etc. Do some microbenchmarking to get an understanding of the impact on people who are using r_f_p for real. The current patchset looks rather alphaish. > The > printk() might maybe (hopefully) get us some reaction in say a years > time, much longer if we're really unlucky. > > That said, we could make the syscall return -ENOSYS unless a sysctl was > touched. The printk() would indeed have to mention said sysctl and a > place to find information about why we're doing this.. > > But by creating more pain (people have to actually set the sysctl, and > we'll have to universally agree to inflict pain on distro people that > set it by default -- say, starve them from beer at the next conf.) we're > more likely to get an answer sooner. Could be. We should consult distro people, Oracle people... -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org