From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760327AbbA2CAI (ORCPT ); Wed, 28 Jan 2015 21:00:08 -0500 Received: from slow1-d.mail.gandi.net ([217.70.178.86]:33622 "EHLO slow1-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754521AbbA2CAD (ORCPT ); Wed, 28 Jan 2015 21:00:03 -0500 X-Greylist: delayed 2400 seconds by postgrey-1.27 at vger.kernel.org; Wed, 28 Jan 2015 21:00:02 EST Date: Wed, 28 Jan 2015 13:51:06 -0800 From: josh@joshtriplett.org To: Pavel Machek Cc: Tom Zanussi , linux-kernel@vger.kernel.org Subject: Re: [PATCH 05/10] drivers/char: Support compiling out /dev/zero Message-ID: <20150128215106.GA6338@cloud> References: <79846ac644fe9103ef9b7cb0ab69e6f196f27853.1422035184.git.tom.zanussi@linux.intel.com> <20150128210751.GA14006@amd> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150128210751.GA14006@amd> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 28, 2015 at 10:07:51PM +0100, Pavel Machek wrote: > On Fri 2015-01-23 12:37:11, Tom Zanussi wrote: > > Some embedded systems with tightly controlled userspace have no use > > for /dev/zero, and could benefit from the size savings gained by > > omitting it. Add a new EMBEDDED config option to disable it. > > > > bloat-o-meter (based on tinyconfig): > > > > add/remove: 0/3 grow/shrink: 0/1 up/down: 0/-391 (-391) > > function old new delta > > chr_dev_init 162 147 -15 > > mmap_zero 16 - -16 > > zero_fops 116 - -116 > > zero_bdi 244 - -244 > > > > Signed-off-by: Tom Zanussi > > I'm not sure that 400 bytes are worth additional Kconfig noise. .. and > pretty much everyone needs /dev/zero... Relatively few, actually, given MMAP_ANONYMOUS. Memory isn't allocated via an mmap of /dev/zero. It's useful for systems with shells that want to redirect from it or read from it, but less useful for environments with entirely compiled code. /dev/null is much more commonly needed, though there are still systems that won't need it (and can just disable read/writes on an fd entirely rather than duping /dev/null to that fd). That said, I'd be entirely in favor of consolidating many of these "miscellaneous character device" options into a couple of Kconfig options. It doesn't seem critical to *individually* control each of these files in /dev. Personally, I'm hoping that we eventually end up with a disableable CONFIG_CHAR similar to CONFIG_BLOCK. - Josh Triplett