From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin LaHaise Subject: Re: [PATCH 1/3] sysfs directory scaling: rbtree for dirent name lookups Date: Tue, 3 Nov 2009 16:52:51 -0500 Message-ID: <20091103215251.GS8227@kvack.org> References: <20091101163130.GA7911@kvack.org> <20091103035058.GA19515@kroah.com> <20091103200155.GQ8227@kvack.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Greg KH , Eric Dumazet , Octavian Purdila , netdev@vger.kernel.org, Cosmin Ratiu , linux-kernel@vger.kernel.org To: "Eric W. Biederman" Return-path: Received: from kanga.kvack.org ([205.233.56.17]:49675 "EHLO kanga.kvack.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752892AbZKCVwr (ORCPT ); Tue, 3 Nov 2009 16:52:47 -0500 Content-Disposition: inline In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Tue, Nov 03, 2009 at 01:32:33PM -0800, Eric W. Biederman wrote: > Are your numbers from your application and are they real world? > In which case they are interesting, but it would be good if > we could also have microbenchmark numbers that just measure > the sysfs costs. If nothing else I am seeing a big startup > overhead that isn't being subtracted out that makes it hard > to see the real costs here. They're application based, so there's a bunch of other overhead included that won't show up on a microbenchmark. Each interface requires a round trip between 2 L2TP daemons, so there are lots of syscalls and other cache polluting effects that won't show up on a microbenchmark. One of the L2TP daemons is configured not to instantiate any kernel state -- running in this mode, it has very little overhead. The other thing to note is that the costs posted are how long it takes to add an additional 5,000 interfaces in the given range, not the total time to add say 35,000 interfaces (I didn't feel like waiting that long). -ben