From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin LaHaise Subject: Re: [PATCH 3/7] sysfs: Keep an nlink count on sysfs directories. Date: Mon, 11 Jan 2010 19:53:08 -0500 Message-ID: <20100112005308.GL5524@kvack.org> References: <1263241315-19499-3-git-send-email-ebiederm@xmission.com> <4B4BC683.7060508@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "Eric W. Biederman" , Greg Kroah-Hartman , Kay Sievers , linux-kernel@vger.kernel.org, Cornelia Huck , linux-fsdevel@vger.kernel.org, Eric Dumazet , Serge Hallyn , "Eric W. Biederman" To: Tejun Heo Return-path: Received: from kanga.kvack.org ([205.233.56.17]:56411 "EHLO kanga.kvack.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754440Ab0ALBPE (ORCPT ); Mon, 11 Jan 2010 20:15:04 -0500 Content-Disposition: inline In-Reply-To: <4B4BC683.7060508@kernel.org> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, Jan 12, 2010 at 09:46:59AM +0900, Tejun Heo wrote: > Hello, > > On 01/12/2010 05:21 AM, Eric W. Biederman wrote: > > On large directories sysfs_count_nlinks can be a significant > > bottleneck, so keep a count in sysfs_dirent. > > I was about to suggest changing s_flags to ushort too. Hmmm... adding > a new field to sysfs_dirent somewhat worries me but this doesn't add > to the size of the structure. How significant bottlenect are we > talking about? 100,000 entries in a sysfs directory is a requirement for network devices. > > If we exceed the maximum number of directory entries we can store > > return nlink of 1. An nlink of 1 matches what reiserfs does in this > > case, and it let's find and similar utlities know that we have a the > > directory nlink can not be used for optimization purposes. > > Hmmm... what's the limit on reiserfs? Is it 64k too? 64k is too small. 10 gig interfaces can currently service 50-100k users, each of which requires their own network device. -ben