Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756215Ab2FNPSN (ORCPT ); Thu, 14 Jun 2012 11:18:13 -0400 Received: from e06smtp14.uk.ibm.com ([195.75.94.110]:50747 "EHLO e06smtp14.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752931Ab2FNPSK (ORCPT ); Thu, 14 Jun 2012 11:18:10 -0400 Date: Thu, 14 Jun 2012 17:18:00 +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: <20120614171800.72f02152@de.ibm.com> In-Reply-To: <20120614134238.GD16848@somewhere> 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> 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: 12061415-1948-0000-0000-000002181265 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2113 Lines: 60 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. -- blue skies, Martin. "Reality continues to ruin my life." - Calvin. -- 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/