Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752363AbYLOM63 (ORCPT ); Mon, 15 Dec 2008 07:58:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750802AbYLOM6V (ORCPT ); Mon, 15 Dec 2008 07:58:21 -0500 Received: from mail-bw0-f21.google.com ([209.85.218.21]:56560 "EHLO mail-bw0-f21.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750793AbYLOM6U (ORCPT ); Mon, 15 Dec 2008 07:58:20 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=message-id:date:from:reply-to:to:subject:cc:in-reply-to :mime-version:content-type:content-transfer-encoding :content-disposition:references; b=EwqIwanHiVc/eOAXy9UqVF5UyUaF15ljcMqTBgjZCX1Ke5iAzXEu0Og9645vwxW85y QlDjMm1n0yA4EAcjUt3yx4o+OIHhaLAVDk/VwplneJznVsPlgt0t9ChlWyEXOrQwE1vW fJYSr1YfGULIGYFvomKt3cevnfQ7a73dUCWcg= Message-ID: <7c86c4470812150458o47292790gf143fb035bf1e06d@mail.gmail.com> Date: Mon, 15 Dec 2008 13:58:18 +0100 From: "stephane eranian" Reply-To: eranian@gmail.com To: "Paul Mackerras" Subject: Re: [patch] Performance Counters for Linux, v3 Cc: "Ingo Molnar" , "Peter Zijlstra" , "Vince Weaver" , linux-kernel@vger.kernel.org, "Thomas Gleixner" , "Andrew Morton" , "Eric Dumazet" , "Robert Richter" , "Arjan van de Veen" , "Peter Anvin" , "David S. Miller" In-Reply-To: <18757.42682.109305.676647@drongo.ozlabs.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20081211155230.GA4230@elte.hu> <1229070345.12883.12.camel@twins> <7c86c4470812120059s7f8e64a6h91ebeadbf938858d@mail.gmail.com> <1229073834.12883.41.camel@twins> <7c86c4470812120942x607a74f7w9f823adecbd73b85@mail.gmail.com> <7c86c4470812121001i765d663bq6db3080b633a1eef@mail.gmail.com> <20081214231332.GA26942@elte.hu> <18757.42682.109305.676647@drongo.ozlabs.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1662 Lines: 46 Hi, On Mon, Dec 15, 2008 at 1:37 AM, Paul Mackerras wrote: > Ingo Molnar writes: > >> * stephane eranian wrote: >> >> > Hi, >> > >> > Given the level of abstractions you are using for the API, and given >> > your argument that the kernel can do the HW resource scheduling better >> > than anybody else. >> > >> > What happens in the following test case: >> > >> > - 2-way system (cpu0, cpu1) >> > >> > - on cpu0, two processes P1, P2, each self-monitoring and counting event E1. >> > Event E1 can only be measured on counter C1. >> > >> > - on cpu1, there is a cpu-wide session, monitoring event E1, thus using C1 >> > >> > - the scheduler decides to migrate P1 onto CPU1. You now have a >> > conflict on C1. >> > >> > How is this managed? >> >> If there's a single unit of sharable resource [such as an event counter, >> or a physical CPU], then there's just three main possibilities: either >> user 1 gets it all, or user 2 gets it all, or they share it. >> >> We've implemented the essence of these variants, with sharing the resource >> being the sane default, and with the sysadmin also having a configuration >> vector to reserve the resource to himself permanently. (There could be >> more variations of this.) >> >> What is your point? >> Could you explain what you mean by sharing here? Are you talking about time multiplexing the counter? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/