From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1AB37C46475 for ; Tue, 20 Nov 2018 21:18:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 97F3D2147D for ; Tue, 20 Nov 2018 21:18:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 97F3D2147D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726456AbeKUHtM (ORCPT ); Wed, 21 Nov 2018 02:49:12 -0500 Received: from mga14.intel.com ([192.55.52.115]:14749 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725926AbeKUHtM (ORCPT ); Wed, 21 Nov 2018 02:49:12 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 20 Nov 2018 13:18:03 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,258,1539673200"; d="scan'208";a="92700723" Received: from tassilo.jf.intel.com (HELO tassilo.localdomain) ([10.7.201.126]) by orsmga006.jf.intel.com with ESMTP; 20 Nov 2018 13:18:03 -0800 Received: by tassilo.localdomain (Postfix, from userid 1000) id 10A063018C4; Tue, 20 Nov 2018 13:18:03 -0800 (PST) Date: Tue, 20 Nov 2018 13:18:03 -0800 From: Andi Kleen To: Kyle Huey Cc: Kan Liang , "Peter Zijlstra (Intel)" , Ingo Molnar , Robert O'Callahan , Alexander Shishkin , Arnaldo Carvalho de Melo , Jiri Olsa , Linus Torvalds , Stephane Eranian , Thomas Gleixner , Vince Weaver , acme@kernel.org, open list Subject: Re: [REGRESSION] x86, perf: counter freezing breaks rr Message-ID: <20181120211803.GF13936@tassilo.jf.intel.com> References: <20181120194129.GC13936@tassilo.jf.intel.com> <20181120201144.GD13936@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > I suppose that's fair that it's better for some use cases. The flip > side is that it's no longer possible to get exactly accurate counts > from user space if you're using the PMI (because any events between > the overflow itself and the transition to the PMI handler are > permanently lost) which is catastrophically bad for us :) Yes that's a fair point. For most usages it doesn't matter. I suspect that's a case for supporting opt-out for freezing per perf event, and rr using that. -Andi