From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262336AbTJFSbO (ORCPT ); Mon, 6 Oct 2003 14:31:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262378AbTJFS31 (ORCPT ); Mon, 6 Oct 2003 14:29:27 -0400 Received: from mtagate2.uk.ibm.com ([195.212.29.135]:14753 "EHLO mtagate2.uk.ibm.com") by vger.kernel.org with ESMTP id S262336AbTJFS3R (ORCPT ); Mon, 6 Oct 2003 14:29:17 -0400 Date: Tue, 7 Oct 2003 00:01:32 +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: <20031006183132.GD1788@in.ibm.com> Reply-To: dipankar@in.ibm.com References: <20031006085915.GE4220@in.ibm.com> <20031006160846.GA4125@us.ibm.com> <20031006173111.GA1788@in.ibm.com> <20031006173858.GA4403@kroah.com> <20031006180119.GC1788@in.ibm.com> <20031006180907.GA4611@kroah.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20031006180907.GA4611@kroah.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 11:09:07AM -0700, Greg KH wrote: > On Mon, Oct 06, 2003 at 11:31:19PM +0530, Dipankar Sarma wrote: > No. My main point is that for every hotplug event (which is caused by a > kobject being created or destroyed), udev will run and look at the sysfs > entry for the kobject (by using libsysfs which reads in all of the > kobject information, including attributes). This is a normal event, so > we have to care about what happens after running 'find' on the sysfs > tree as that is basically what will always happen. > > Does that make more sense? We can't just look at what happens with this > patch without actually accessing all of the sysfs tree, as that will be > the "normal" case. That sounds odd. So, udev essentially results in a frequent and continuous "find /sys" ? That doesn't sound good. You are unnecessarily adding pressure on vfs (dcache specially). We will discuss this offline then and see what needs to be done. > > > Can you show this happening? > > > > It should be easy to demonstrate. That is how dentries/inodes > > work for on-disk filesystems. If Maneesh's patch didn't work that > > way, then the whole point is lost. I hope that is not the case. > > Me too. It's just that the free memory numbers didn't show much gain > with this patch on his system. That worries me. Well, Maneesh didn't post numbers after letting the system age out sysfs dentries/inodes. Maneesh can you post some such numbers ? > > > But again, I don't think the added overhead you have added to a kobject > > > is acceptable for not much gain for the normal case (systems without a > > > zillion devices.) > > > > IIRC, Maneesh test machine is a 2-way P4 xeon with six scsi disks and savings > > are of about 800KB. That is as normal a case as it gets, I think. > > It only gets better as you have more devices in your system. > > 800Kb after running find? I don't see that :) No, those numbers were for just mounting sysfs. More numbers tomorrow. Thanks Dipankar