Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756548Ab2FORh3 (ORCPT ); Fri, 15 Jun 2012 13:37:29 -0400 Received: from mail-gh0-f174.google.com ([209.85.160.174]:37972 "EHLO mail-gh0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752210Ab2FORh2 (ORCPT ); Fri, 15 Jun 2012 13:37:28 -0400 Date: Fri, 15 Jun 2012 19:37:18 +0200 From: Frederic Weisbecker To: Martin Schwidefsky 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: <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120614171800.72f02152@de.ibm.com> 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: 2524 Lines: 63 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()? -- 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/