From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932533AbaHEIIf (ORCPT ); Tue, 5 Aug 2014 04:08:35 -0400 Received: from mail-pa0-f52.google.com ([209.85.220.52]:41513 "EHLO mail-pa0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932516AbaHEIIc (ORCPT ); Tue, 5 Aug 2014 04:08:32 -0400 Date: Tue, 5 Aug 2014 08:12:47 +0000 From: Minchan Kim To: Karel Zak Cc: Sami Kerola , util-linux@vger.kernel.org, Timofey Titovets , Nitin Gupta , Sergey Senozhatsky , linux-kernel@vger.kernel.org Subject: Re: zram: device management utility needed Message-ID: <20140805081238.GA3700@gmail.com> References: <1406675682-8402-1-git-send-email-kerolasa@iki.fi> <20140805020024.GB27993@bbox> <20140805070716.GB12104@x2.net.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140805070716.GB12104@x2.net.home> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 05, 2014 at 09:07:16AM +0200, Karel Zak wrote: > On Tue, Aug 05, 2014 at 11:00:24AM +0900, Minchan Kim wrote: > > On Wed, Jul 30, 2014 at 12:14:42AM +0100, Sami Kerola wrote: > > > The zram devices are not created by any sort of equipment appearing in a > > > bus so an method of creating new or removing existing devices will be > > > needed. When the zram module is loaded it should create > > > /dev/zram-control device, that responds to ioctl() calls[4]. The calls > > > could be similar with /dev/loop-control[5], that allow adding or removing > > > specified device, and discover adding a free device. > > > > Normally, dynamic management is good to have, I think but I didn't hear > > strong requirement for that until now. > > I guess that number of zram devices will be always relatively small > compare to /dev/loopN devices. It is not unusual that people use > systems with more than 256 loop devs, so /dev/loop-control makes a lot > of sense to keep the device management effective and simple. > > > Why don't you change num_device param at module loading time? > > If you have really many loopN devices than create all the nodes at > boot time means extra overhead (allocate nodes in kernel, events to > udev, create /dev files etc.). The ioctl LOOP_CTL_* API also provides > LOOP_CTL_GET_FREE that returns unused device, so you don't have to > scan all the /dev/loopN devices to detect a free device. Thanks for the info! > > > I'd like to hear real scenario from whom are about to using that faeture > > right now and what's the problem with num_device param. > > Again, I don't think it's so important for zram as for loop devices. > All depends how people will use zram devices. We will see... Yeb and we can do it when we see. > > Karel > > -- > Karel Zak > http://karelzak.blogspot.com