From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756450AbZETKEi (ORCPT ); Wed, 20 May 2009 06:04:38 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755141AbZETKE1 (ORCPT ); Wed, 20 May 2009 06:04:27 -0400 Received: from mailbox-us-s-12.mailhostingserver.com ([75.125.101.9]:58675 "EHLO mailbox-us-s-12.mailhostingserver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756070AbZETKEZ (ORCPT ); Wed, 20 May 2009 06:04:25 -0400 Date: Wed, 20 May 2009 12:04:23 +0200 From: Matthias Kaehlcke To: Marcin Krol Cc: linux-kernel@vger.kernel.org Subject: Re: inotify limits - thousands (tens of thousands?) of watches Message-ID: <20090520100423.GA3695@traven> Mail-Followup-To: Matthias Kaehlcke , Marcin Krol , linux-kernel@vger.kernel.org References: <4A13CCE1.5000106@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4A13CCE1.5000106@gmail.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org El Wed, May 20, 2009 at 11:26:57AM +0200 Marcin Krol ha dit: > First, apols for using up bandwidth, but I honestly found no other place > where I can ask about this (and get meaningful reply). > > I'm not a kernel programmer, but I want to develop a program that would > watch modifications in *all* user directories on a busy server using > inotify. > > This is for high-availability purposes - events would be collected and > once every several minutes changed dirs would be rsync'ed to failover > server or smth like that would be done. > > As inotify watches particular directory and not its subdirs, I would > have to watch all directories. > > This means I would have to create thousands or even tens of thousands of > inotify watches. > > So my questions are: > > 1. is it safe? that is, will it not lock the kernel up, or cause > excessive memory consumption? > > 2. is it economic in terms of CPU time and RAM? I have no idea how to > even measure such a thing happening in the kernel.. i can't answer your question whether inotify scales or not, but maybe DRBD (http://en.wikipedia.org/wiki/DRBD) could be an alternative approach for your problem -- Matthias Kaehlcke Embedded Linux Engineer Barcelona Me lo contaron y lo olvidé, lo vi y lo entendí, lo hice y lo aprendí (Confucio) .''`. using free software / Debian GNU/Linux | http://debian.org : :' : `. `'` gpg --keyserver pgp.mit.edu --recv-keys 47D8E5D4 `-