Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1753958AbdIDPm6 (ORCPT <rfc822;w@1wt.eu>);
        Mon, 4 Sep 2017 11:42:58 -0400
Received: from merlin.infradead.org ([205.233.59.134]:45426 "EHLO
        merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1753842AbdIDPmH (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Mon, 4 Sep 2017 11:42:07 -0400
Date: Mon, 4 Sep 2017 17:41:45 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Andi Kleen <ak@linux.intel.com>, Kan Liang <kan.liang@intel.com>,
        Dmitri Prokhorov <Dmitry.Prohorov@intel.com>,
        Valery Cherepennikov <valery.cherepennikov@intel.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Stephane Eranian <eranian@google.com>,
        David Carrillo-Cisneros <davidcc@google.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Vince Weaver <vince@deater.net>, Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [RFC][PATCH] perf: Rewrite enabled/running timekeeping
Message-ID: <20170904154145.xl4fyg7vhgbnmhwi@hirez.programming.kicks-ass.net>
References: <96c7776f-1f17-a39e-23e9-658596216d6b@linux.intel.com>
 <bb431829-bf5d-8278-131d-a41f0001e594@linux.intel.com>
 <20170803150052.za2vofyqfgarukdr@hirez.programming.kicks-ass.net>
 <c052d929-db1d-8b31-4a62-07563d48063b@linux.intel.com>
 <20170822204743.GR32112@worktop.programming.kicks-ass.net>
 <2a426aa2-42c8-e839-1cec-aa3971651f3e@linux.intel.com>
 <20170831171837.njnc6r6elsvkl7lt@hirez.programming.kicks-ass.net>
 <46f72a3f-f18b-0227-3d78-fb23c8a6e18e@linux.intel.com>
 <20170904120843.oazlv73phoxoinlj@hirez.programming.kicks-ass.net>
 <385005b6-51ea-383e-df81-43365f3f5152@linux.intel.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <385005b6-51ea-383e-df81-43365f3f5152@linux.intel.com>
User-Agent: NeoMutt/20170609 (1.8.3)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 969
Lines: 26

On Mon, Sep 04, 2017 at 05:56:06PM +0300, Alexey Budankov wrote:
> On 04.09.2017 15:08, Peter Zijlstra wrote:
> > On Mon, Sep 04, 2017 at 01:46:45PM +0300, Alexey Budankov wrote:
> >>> So the below completely rewrites timekeeping (and probably breaks
> >>> world) but does away with the need to touch events that don't get
> >>> scheduled.
> >>
> >> We still need and do iterate thru all events at some points e.g. on context switches.
> > 
> > Why do we _need_ to?
> 
> We do so in the current implementation with several tstamp_* fields.

Right, but we want to stop doing so asap :-)


> >> U - allocation, A - ACTIVE, I - INACTIVE, O - OFF, 
> >> E - ERROR, X - EXIT, D - DEAD,
> > 
> > Not sure we care about the different <0 values, they're all effectively
> > OFF.
> 
> We still need to care about proper initial state of timings when moving above >=0 state.

Very true. I'm not sure I fully covered that, let me see if there's
something sensible to do for that.