From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261981AbUFVKVK (ORCPT ); Tue, 22 Jun 2004 06:21:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261987AbUFVKVK (ORCPT ); Tue, 22 Jun 2004 06:21:10 -0400 Received: from zero.aec.at ([193.170.194.10]:51462 "EHLO zero.aec.at") by vger.kernel.org with ESMTP id S261981AbUFVKVG (ORCPT ); Tue, 22 Jun 2004 06:21:06 -0400 To: Andrew Morton cc: mikpe@csd.uu.se, linux-kernel@vger.kernel.org Subject: Re: [PATCH][1/6] perfctr-2.7.3 for 2.6.7-rc1-mm1: core References: <223si-461-9@gated-at.bofh.it> <29Piu-4H4-27@gated-at.bofh.it> From: Andi Kleen Date: Tue, 22 Jun 2004 12:21:01 +0200 In-Reply-To: <29Piu-4H4-27@gated-at.bofh.it> (Andrew Morton's message of "Tue, 22 Jun 2004 11:00:14 +0200") Message-ID: User-Agent: Gnus/5.110003 (No Gnus v0.3) Emacs/21.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org [few points I just noticed] Andrew Morton writes: > > - a general overview of how the whole thing operates (what's > PERFCTR_INTERRUPT_SUPPORT do? What interrupts are generated? Describe The hardware can usually generate an interrupt when the performance counter under or overflows. oprofile uses this too. > the backpatching design, etc). What is "forbidden" on p4 siblings, and p4 siblings share only a single set of performance counters, so you must keep them synchronized. > > - cannot cpus_copy_to_user() share code with > sys_sched_getaffinity()? The sched_getaffinity code for that is broken, I'm about to submit a patch for it. I haven't looked at that one. > > - Is there much point in making CONFIG_PERFCTR_VIRTUAL optional? It slows down an important fast path (context switch) But it would be better to use some back patching design like kernel hooks to keep the cost for the common case (no perfctr getting switched) low. If that common case can be kept at a "no checks at all" level then it's good. That would be best for distribution kernels too. -Andi