Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753587AbaBZS7q (ORCPT ); Wed, 26 Feb 2014 13:59:46 -0500 Received: from mail-ve0-f177.google.com ([209.85.128.177]:61118 "EHLO mail-ve0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753367AbaBZS7o (ORCPT ); Wed, 26 Feb 2014 13:59:44 -0500 MIME-Version: 1.0 In-Reply-To: <20140226185513.GL22728@two.firstfloor.org> References: <1392703661-15104-1-git-send-email-zheng.z.yan@intel.com> <530D53EF.9090706@amacapital.net> <20140226185513.GL22728@two.firstfloor.org> From: Andy Lutomirski Date: Wed, 26 Feb 2014 10:59:17 -0800 Message-ID: Subject: Re: [PATCH v3 00/14] perf, x86: Haswell LBR call stack support To: Andi Kleen Cc: Stephane Eranian , "Yan, Zheng" , LKML , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Feb 26, 2014 at 10:55 AM, Andi Kleen wrote: >> I'm suggesting a perf event option, just like the way that PEBS works. > > Right now it's a somewhat experimental feature and just having > the sysctl is fine. If it turns out that is what everyone uses > such an option could be still added later. I'm a bit worried that the syscall will be stuck as ABI forever, though. Its presence will make adding a different configuration mechanism awkward. > > I suspect most people would still use FP if they can, just use > the LBRs if that doesn't work. I wonder if anyone who uses perf for userspace profiling *ever* uses FP and gets away with it. There's precious little userspace software compiled with frame pointers these days on most architectures. I have a concrete reason for this question: it would be nice to compile the vDSO with frame pointers off. IIRC there would be a significant performance gain, and I think the only thing that would break is perf. But it looks like perf will have nice elfutils unwind support in 3.15, and if FP support is useless anyway... --Andy -- 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/