Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933343Ab2HPUzt (ORCPT ); Thu, 16 Aug 2012 16:55:49 -0400 Received: from mail.x86-64.org ([217.9.48.20]:53189 "EHLO mail.x86-64.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754119Ab2HPUzr (ORCPT ); Thu, 16 Aug 2012 16:55:47 -0400 Date: Thu, 16 Aug 2012 22:55:39 +0200 From: Borislav Petkov To: Jonathan Corbet Cc: Peter Zijlstra , Ingo Molnar , Steven Rostedt , Frederic Weisbecker , LKML , Borislav Petkov Subject: Re: [RFC PATCH -v2 0/4] Persistent events Message-ID: <20120816205539.GA16308@aftab.osrc.amd.com> References: <1345139123-15212-1-git-send-email-bp@amd64.org> <20120816141253.0142ddd0@lwn.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120816141253.0142ddd0@lwn.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2189 Lines: 59 Hi Jon, On Thu, Aug 16, 2012 at 02:12:53PM -0600, Jonathan Corbet wrote: > On Thu, 16 Aug 2012 19:45:19 +0200 > Borislav Petkov wrote: > > > off and on I get some free time to work on that, here's the latest > > incarnation. It contains review feedback from the earlier round. > > Can I add one small request for the next round? I've looked through the > patches and the code a bit, and I still have absolutely no clue of what a > "persistent event" is or why I might want one. Now, admittedly, I'm > slower than most, but it still might not hurt to add some overall > description of what this is for...? yeah, maybe the naming is not the most fitting one but here's the basic idea: Normally, you enable perf events for a duration of time where you trace your workload and then you disable them. In contrast, persistent events are perf events which you enable at system boot and they remain enabled - thus persistent - during the whole system lifetime. The machinery logs all events and carries them out to userspace. Much like the blackbox of a plane which records system events during the whole flight. And the usecase here is that we want the machine check code to log machine checks during the whole system lifetime using the perf/trace events infrastructure. And this happens regardless of whether there's a userspace consumer of the logged data. Normally, we'll have one though :). MCA and the trace_mce_record() tracepoint is thus is the first user of the persistent events but there might be others. Please follow this thread: http://marc.info/?l=linux-kernel&m=133234057614885 for some more thoughts on the idea. Of course, this whole thing is basically a rough draft and we're still hammering out the details as we go. Thanks. -- Regards/Gruss, Boris. Advanced Micro Devices GmbH Einsteinring 24, 85609 Dornach GM: Alberto Bozzo Reg: Dornach, Landkreis Muenchen HRB Nr. 43632 WEEE Registernr: 129 19551 -- 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/