From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263573AbTDCXcd (for ); Thu, 3 Apr 2003 18:32:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263574AbTDCXcd (for ); Thu, 3 Apr 2003 18:32:33 -0500 Received: from [12.47.58.55] ([12.47.58.55]:12704 "EHLO pao-ex01.pao.digeo.com") by vger.kernel.org with ESMTP id S263573AbTDCXcc (for ); Thu, 3 Apr 2003 18:32:32 -0500 Date: Thu, 3 Apr 2003 15:43:14 -0800 From: Andrew Morton To: Badari Pulavarty Cc: linux-kernel@vger.kernel.org Subject: Re: mounting 4000 disks Message-Id: <20030403154314.7b8604c9.akpm@digeo.com> In-Reply-To: <200304031520.52138.pbadari@us.ibm.com> References: <200304031520.52138.pbadari@us.ibm.com> X-Mailer: Sylpheed version 0.8.10 (GTK+ 1.2.10; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 03 Apr 2003 23:43:55.0761 (UTC) FILETIME=[E3DACE10:01C2FA3A] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Badari Pulavarty wrote: > > Hi, > > I have been playing with testing 4000 disk support. (using 32bit dev_t). > > I created 4000 disks using scsi_debug and mounted them. > We consumed 84MB of low memory by just mouting 4000 filesystems. > Out of 84MB lowmem 48MB is in slabs. 33 MB is used by buffers. 20 kbytes per disk+filesystem seems reasonable. The "Buffers" will be the superblock (4k) and the group descriptor blocks (256 bytes per gigabyte of disk). These are pinned memory. And the ext2 superblock got bigger in -mm due to the recent scalability patches. What is using the "size-8192" allocation there? It could be the ext2 superblock if you have NR_CPUS=32.