From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751646Ab1JMUPt (ORCPT ); Thu, 13 Oct 2011 16:15:49 -0400 Received: from mx2.parallels.com ([64.131.90.16]:42175 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751096Ab1JMUPs (ORCPT ); Thu, 13 Oct 2011 16:15:48 -0400 Message-ID: <4E9746B0.7030603@parallels.com> Date: Fri, 14 Oct 2011 00:14:40 +0400 From: Glauber Costa User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:7.0) Gecko/20110927 Thunderbird/7.0 MIME-Version: 1.0 To: David Miller CC: , , , , , , , , , , , Subject: Re: [PATCH v7 0/8] Request for inclusion: tcp memory buffers References: <1318511382-31051-1-git-send-email-glommer@parallels.com> <20111013.160031.605700447623532119.davem@davemloft.net> <4E9744A6.5010101@parallels.com> <20111013.161221.1969725742975317077.davem@davemloft.net> In-Reply-To: <20111013.161221.1969725742975317077.davem@davemloft.net> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [195.68.147.2] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/14/2011 12:12 AM, David Miller wrote: > From: Glauber Costa > Date: Fri, 14 Oct 2011 00:05:58 +0400 > >> Also, I kind of dispute the affirmation that !cgroup will encompass >> the majority of users, since cgroups is being enabled by default by >> most vendors. All systemd based systems use it extensively, for >> instance. > > I will definitely advise people against this, since the cost of having > this on by default is absolutely non-trivial. > > People keep asking every few releases "where the heck has my performance > gone" and it's because of creeping features like this. This socket > cgroup feature is a prime example of where that kind of stuff comes > from. > > I really get irritated when people go "oh, it's just one indirect > function call" and "oh, it's just one more pointer in struct sock" > > We work really hard to _remove_ elements from structures and make them > smaller, and to remove expensive operations from the fast paths. > > It might take someone weeks if not months to find a way to make a > patch which compensates for the extra overhead your patches are adding. > > And I don't think you fully appreciate that. Let's focus on this: Are you happy, or at least willing to accept, an approach that keep things as they were with cgroups *compiled out*, or were you referring to not in use == compiled in, but with no users?