From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752528Ab1LSK43 (ORCPT ); Mon, 19 Dec 2011 05:56:29 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:43113 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752228Ab1LSK4Z (ORCPT ); Mon, 19 Dec 2011 05:56:25 -0500 Date: Mon, 19 Dec 2011 11:54:29 +0100 From: Ingo Molnar To: Robert Richter Cc: Benjamin Block , Hans Rosenfeld , hpa@zytor.com, tglx@linutronix.de, suresh.b.siddha@intel.com, eranian@google.com, brgerst@gmail.com, Andreas.Herrmann3@amd.com, x86@kernel.org, linux-kernel@vger.kernel.org, Benjamin Block Subject: Re: [RFC 4/5] x86, perf: implements lwp-perf-integration (rc1) Message-ID: <20111219105429.GC19861@elte.hu> References: <20111216160757.GL665@escobedo.osrc.amd.com> <1324051943-21112-1-git-send-email-hans.rosenfeld@amd.com> <1324051943-21112-4-git-send-email-hans.rosenfeld@amd.com> <20111218080443.GB4144@elte.hu> <20111218234309.GA12958@elte.hu> <20111219090923.GB16765@erda.amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20111219090923.GB16765@erda.amd.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.3.1 -2.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Robert Richter wrote: > On 19.12.11 00:43:10, Ingo Molnar wrote: > > > So the question becomes, how well is it integrated: can perf > > 'record -a + perf report', or 'perf top' use LWP, to do > > system-wide precise [user-space] profiling and such? > > There is only self-monitoring of a process possible, no kernel > and system-wide profiling. This is because we can not allocate > memory regions in the kernel for a thread other than the > current. This would require a complete rework of mm code. Hm, i don't think a rework is needed: check the vmalloc_to_page() code in kernel/events/ring_buffer.c. Right now CONFIG_PERF_USE_VMALLOC is an ARM, MIPS, SH and Sparc specific feature, on x86 it turns on if CONFIG_DEBUG_PERF_USE_VMALLOC=y. That should be good enough for prototyping the kernel/user shared buffering approach. Thanks, Ingo