From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754462Ab0CVLX4 (ORCPT ); Mon, 22 Mar 2010 07:23:56 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:56997 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750997Ab0CVLXy (ORCPT ); Mon, 22 Mar 2010 07:23:54 -0400 Date: Mon, 22 Mar 2010 12:23:40 +0100 From: Ingo Molnar To: Avi Kivity Cc: Anthony Liguori , Pekka Enberg , "Zhang, Yanmin" , Peter Zijlstra , Sheng Yang , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Marcelo Tosatti , oerg Roedel , Jes Sorensen , Gleb Natapov , Zachary Amsden , ziteng.huang@intel.com, Arnaldo Carvalho de Melo , Fr?d?ric Weisbecker Subject: Re: [RFC] Unify KVM kernel-space and user-space code into a single project Message-ID: <20100322112340.GD3483@elte.hu> References: <20100318172805.GB26067@elte.hu> <4BA32E1A.2060703@redhat.com> <20100319085346.GG12576@elte.hu> <4BA3747F.60401@codemonkey.ws> <20100321191742.GD25922@elte.hu> <4BA67B2F.4030101@redhat.com> <20100321203121.GA30194@elte.hu> <4BA6900B.1040408@redhat.com> <20100321215207.GA13219@elte.hu> <4BA712F0.5030806@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4BA712F0.5030806@redhat.com> User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: 0.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=0.0 required=5.9 tests=none autolearn=no SpamAssassin version=3.2.5 _SUMMARY_ Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Avi Kivity wrote: > IMO the reason perf is more usable than oprofile has less to do with the > kernel/userspace boundary and more do to with effort and attention spent on > the userspace/user boundary. > > [...] If you are interested in the first-hand experience of the people who are doing the perf work then here it is: by far the biggest reason for perf success and perf usability is the integration of the user-space tooling with the kernel-space bits, into a single repository and project. The very move you are opposing so vehemently for KVM. Oprofile went the way you proposed, and it was a failure. It failed not because it was bad technology (it was pretty decent and people used it), it was not a failure because the wrong people worked on it (to the contrary, very capable people worked on it), it was a failure in hindsight because it simply incorrectly split into two projects which stiffled the progress of each other. Obviously 3 years ago you'd have seen a similar, big "Oprofile is NOT broken!" flamewar, had i posted the same observations about Oprofile that i expressed about KVM here. (In fact there was a similar, big flamewar about all this when perf was posted a year ago.) And yes, (as you are aware of) i see very similar patterns of inefficiency in the KVM/Qemu tooling relationship as well, hence did i express my views about it. Thanks, Ingo