From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750815AbWDKOCP (ORCPT ); Tue, 11 Apr 2006 10:02:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750817AbWDKOCP (ORCPT ); Tue, 11 Apr 2006 10:02:15 -0400 Received: from e4.ny.us.ibm.com ([32.97.182.144]:19140 "EHLO e4.ny.us.ibm.com") by vger.kernel.org with ESMTP id S1750815AbWDKOCO (ORCPT ); Tue, 11 Apr 2006 10:02:14 -0400 Date: Tue, 11 Apr 2006 09:01:46 -0500 From: "Serge E. Hallyn" To: Kirill Korotaev Cc: "Serge E. Hallyn" , linux-kernel@vger.kernel.org, herbert@13thfloor.at, sam@vilain.net, "Eric W. Biederman" , xemul@sw.ru, James Morris Subject: Re: [RFC][PATCH 0/5] uts namespaces: Introduction Message-ID: <20060411140146.GB10610@sergelap.austin.ibm.com> References: <20060407095132.455784000@sergelap> <443BA1D3.1070200@sw.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <443BA1D3.1070200@sw.ru> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Quoting Kirill Korotaev (dev@sw.ru): > Serge, > > >This patchset is based on Kirill Korotaev's Mar 24 submission, taking > >comments (in particular from James Morris and Eric Biederman) into > >account. > thanks a lot for doing this! NP, thanks for doing the first round. > >Some performance results are attached. I was mainly curious whether > >it would be worth putting the task_struct->uts_ns pointer inside > >a #ifdef CONFIG_UTS_NS. The result show that leaving it in when > >CONFIG_UTS_NS=n has negligable performance impact, so that is the > >approach this patch takes. > Serge, your testing approach looks really strange for me. > First of all, you selected the worst namespace to check performance > overhead on. > 1) uts_ns is rarely used and never used on hot paths, > 2) also all these test suites below doesn't test the code paths you > modified. > > So I wonder what was the goal of these tests, especially dbench?! Right, I wasn't actually aiming to test the performance of the uts namespaces themselves (despite including those numbers), since they're not on hot paths. I was mostly curious whether putting the utsns pointer into the task_struct would affect performance at all, to know whether to put that inside an #ifdef. Based on the results, I kept it non-#ifdefed even if !CONFIG_UTS_NS, and that's what I was justifying with those numbers. These tests should be done again when we get 3 or 5 namespace pointers, and perhaps there should still be some other tests included, ie mainly a forkbomb perhaps. I just did my default set of tests that I usually use. thanks, -serge