From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751125Ab2FRKqt (ORCPT ); Mon, 18 Jun 2012 06:46:49 -0400 Received: from e06smtp17.uk.ibm.com ([195.75.94.113]:54985 "EHLO e06smtp17.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750786Ab2FRKqr (ORCPT ); Mon, 18 Jun 2012 06:46:47 -0400 Date: Mon, 18 Jun 2012 12:46:29 +0200 From: Martin Schwidefsky To: Frederic Weisbecker Cc: Thomas Gleixner , Ingo Molnar , Peter Zijlstra , LKML , Alessio Igor Bogani , Andrew Morton , Avi Kivity , Chris Metcalf , Christoph Lameter , Daniel Lezcano , Geoff Levand , Gilad Ben Yossef , Hakan Akkan , Kevin Hilman , Max Krasnyansky , "Paul E. McKenney" , Stephen Hemminger , Steven Rostedt , Sven-Thorsten Dietrich , Benjamin Herrenschmidt , "Luck,Tony" Subject: Re: [RFC GIT PULL] nohz: Basic cputime accounting for adaptive tickless Message-ID: <20120618124629.77d2c178@de.ibm.com> In-Reply-To: <20120615173713.GA23238@somewhere.redhat.com> References: <1339604397-8758-1-git-send-email-fweisbec@gmail.com> <1339664829.2559.14.camel@twins> <20120614111241.GA16848@somewhere> <20120614111638.GA16676@gmail.com> <20120614112241.GB16848@somewhere> <20120614144815.1401af49@de.ibm.com> <20120614134238.GD16848@somewhere> <20120614171800.72f02152@de.ibm.com> <20120615173713.GA23238@somewhere.redhat.com> Organization: IBM Corporation X-Mailer: Claws Mail 3.8.0 (GTK+ 2.24.10; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit x-cbid: 12061810-0542-0000-0000-00000230B6E1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 15 Jun 2012 19:37:18 +0200 Frederic Weisbecker wrote: > On Thu, Jun 14, 2012 at 05:18:00PM +0200, Martin Schwidefsky wrote: > > On Thu, 14 Jun 2012 15:42:44 +0200 > > Frederic Weisbecker wrote: > > > > > On Thu, Jun 14, 2012 at 02:48:15PM +0200, Martin Schwidefsky wrote: > > > > On Thu, 14 Jun 2012 13:22:45 +0200 > > > > Frederic Weisbecker wrote: > > > > > > > > > On Thu, Jun 14, 2012 at 01:21:23PM +0200, Thomas Gleixner wrote: > > > > > > On Thu, 14 Jun 2012, Ingo Molnar wrote: > > > > > > > * Frederic Weisbecker wrote: > > > > > > > > You're right, I should have looked into CONFIG_VIRT_CPU_ACCOUNTING sooner > > > > > > > > and see if I can reuse it. > > > > > > > > > > > > > > > > I'll try something with that. > > > > > > > > > > > > > > Maybe sanitize all the variants under a single set of > > > > > > > wrappers/callbacks? > > > > > > > > > > > > Yes, please! > > > > > > > > > > Sure, I'm working in it. > > > > > > > > Please keep me in the loop, I want to avoid that things break on s390. Thanks. > > > > > > Do you have any idea why s390 counts idle time from asm deep in the idle code > > > rather than just hooking in account_system_vtime() like ppc or ia64? > > > > Well what is idle time? For s390 it is the difference in the TOD clock between > > the instruction that loaded the enabled-wait-PSW and the first instruction on > > the interrupt handler. To get the best precision you need to get the TOD time > > stamps as close to these two instructions as possible. For s390 it is the > > following sequence: > > > > STCK __IDLE_ENTER(%r2) # idle enter time stamp > > ltr %r5,%r5 > > stpt __VQ_IDLE_ENTER(%r3) > > jz psw_idle_lpsw > > spt 0(%r1) > > psw_idle_lpsw: > > lpswe __SF_EMPTY(%r15) > > > > <<< sleeping >>> > > > > int_handler: > > STCK __LC_INT_CLOCK # idle exit time stamp > > > > There are at maximum 5 instructions between the STCK for the idle > > enter time stamp and the lpswe that puts the cpu to sleep. > > I see. So s390 accounts only the time spent in low power mode whereas > ppc/ia64 accounts everything that happens in the idle task. > > I don't know which one has chosen the right semantics but this complicates > any possible unification. > > BTW, aren't you accounting the idle time as system time as well with > account_sys_vtime()? No, the accout_sys_vtime call is there to account for the time spent going in and out if idle. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin.