Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933156AbbGUUBz (ORCPT ); Tue, 21 Jul 2015 16:01:55 -0400 Received: from mail-ie0-f179.google.com ([209.85.223.179]:33858 "EHLO mail-ie0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755499AbbGUUBw (ORCPT ); Tue, 21 Jul 2015 16:01:52 -0400 From: Vince Weaver X-Google-Original-From: Vince Weaver Date: Tue, 21 Jul 2015 16:08:28 -0400 (EDT) To: Peter Zijlstra cc: Vince Weaver , linux-kernel@vger.kernel.org, Ingo Molnar , Arnaldo Carvalho de Melo Subject: Re: perf: multiplexing broken on amd fam16h? In-Reply-To: <20150721193224.GW19282@twins.programming.kicks-ass.net> Message-ID: References: <20150721193224.GW19282@twins.programming.kicks-ass.net> User-Agent: Alpine 2.20 (DEB 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1462 Lines: 38 On Tue, 21 Jul 2015, Peter Zijlstra wrote: > On Tue, Jul 21, 2015 at 02:14:54PM -0400, Vince Weaver wrote: > > Hello > > > > I have a new AMD A8 system and perf multiplexing support is acting weird. > > > > If I run the perf_event_tests check_multiplexing test it fails like this: > > > > Event TotalCount RawCount Scale ScaledCount Error > > 0 500282143 150403975 -2.00 (c8050b5 fffffffff9c224ef) -300807950 160.13% > > > > So the problem is that the TOTAL_TIME_RUNNING value is negative, which as > > far as I know shouldn't be possible. > > Correct, that should not happen. I don't have a Fam16 machine, but I can > try and stare at the code a wee bit. Although there's another few perf > issues I am still looking into as well :/ well I've traced it back to see that in update_event_times() run_end is less than event->tstamp_running, which is why the result is negative. [ 1279.857205] VMW: 1 run_end=1279846999345 tstamp_running=1279929016607 [ 1279.857222] VMW: 0 run_end=1279855184453 tstamp_running=1279931111760 It seems to happen both in the PERF_EVENT_STATE_INACTIVE and !PERF_EVENT_STATE_INACTIVE cases. tracking back why those values are wrong is proving to be a bit trickier. Vince -- 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/