From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262464AbTJFR3K (ORCPT ); Mon, 6 Oct 2003 13:29:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262490AbTJFR3K (ORCPT ); Mon, 6 Oct 2003 13:29:10 -0400 Received: from mtagate7.uk.ibm.com ([195.212.29.140]:11918 "EHLO mtagate7.uk.ibm.com") by vger.kernel.org with ESMTP id S262464AbTJFR3G (ORCPT ); Mon, 6 Oct 2003 13:29:06 -0400 Date: Mon, 6 Oct 2003 23:01:11 +0530 From: Dipankar Sarma To: Greg KH Cc: Maneesh Soni , Al Viro , Patrick Mochel , LKML Subject: Re: [RFC 0/6] Backing Store for sysfs Message-ID: <20031006173111.GA1788@in.ibm.com> Reply-To: dipankar@in.ibm.com References: <20031006085915.GE4220@in.ibm.com> <20031006160846.GA4125@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20031006160846.GA4125@us.ibm.com> User-Agent: Mutt/1.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 06, 2003 at 09:08:46AM -0700, Greg KH wrote: > On Mon, Oct 06, 2003 at 02:29:15PM +0530, Maneesh Soni wrote: > > > > 2.6.0-test6 With patches. > > ----------------- > > dentry_cache (active) 2520 2544 > > inode_cache (active) 1058 1050 > > LowFree 875032 KB 874748 KB > > So with these patches we actually eat up more LowFree if all sysfs > entries are searched, and make the dentry_cache bigger? That's not good :( My guess is that those 24 dentries are just noise. What we should do is verify with a large number of devices if the numbers are all that different after a walk of the sysfs tree. > > Remember, every kobject that's created will cause a call to > /sbin/hotplug which will cause udev to walk the sysfs tree to get the > information for that kobject. So I don't see any savings in these > patches, do you? Assuming that unused files/dirs are aged out of dentry and inode cache, it should benefit. The numbers you should look at are - -------------------------------------------------------- After mounting sysfs ------------------- dentry_cache (active) 2350 1321 inode_cache (active) 1058 31 LowFree 875096 KB 875836 KB -------------------------------------------------------- That saves ~800KB. If you just mount sysfs and use a few files, you aren't eating up dentries and inodes for every file in sysfs. How often do you expect hotplug events to happen in a system ? Some time after a hotplug event, dentries/inodes will get aged out and then you should see savings. It should greatly benefit in a normal system. Now if the additional kobjects cause problems with userland hotplug, then that needs to be resolved. However that seems to be a different problem altogether. Could you please elaborate on that ? Thanks Dipankar