From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763333AbXGWJPf (ORCPT ); Mon, 23 Jul 2007 05:15:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752862AbXGWJP2 (ORCPT ); Mon, 23 Jul 2007 05:15:28 -0400 Received: from mtagate4.de.ibm.com ([195.212.29.153]:53661 "EHLO mtagate4.de.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750756AbXGWJP0 (ORCPT ); Mon, 23 Jul 2007 05:15:26 -0400 Subject: Re: [PATCH] virtual sched_clock() for s390 From: Jan Glauber To: Ingo Molnar Cc: Paul Mackerras , Jeremy Fitzhardinge , LKML , vatsa@linux.vnet.ibm.com, mschwid2@linux.vnet.ibm.com, efault@gmx.de, dmitry.adamushko@gmail.com, anton@samba.org In-Reply-To: <20070720072245.GA4020@elte.hu> References: <1184842661.6546.14.camel@localhost.localdomain> <469F8342.7060000@goop.org> <20070719160025.GA31815@elte.hu> <18080.2390.42425.852087@cargo.ozlabs.ibm.com> <20070720072245.GA4020@elte.hu> Content-Type: text/plain Date: Mon, 23 Jul 2007 09:15:49 +0000 Message-Id: <1185182149.5783.11.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.6.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2007-07-20 at 09:22 +0200, Ingo Molnar wrote: > * Paul Mackerras wrote: > > As with s390, 64-bit PowerPC also uses CONFIG_VIRT_CPU_ACCOUNTING. > > That affects how tsk->utime and tsk->stime are accumulated (we call > > account_user_time and account_system_time directly rather than calling > > update_process_times) as well as the system hardirq/softirq time, idle > > time, and stolen time. > > tsk->utime and tsk->stime is only used for a single purpose: to > determine the 'split' factor of how to split up the precise total time > between user and system time. > > > When you say "precise task statistics for /proc", where are they > > accumulated? I don't see any changes to the way that tsk->utime and > > ctime are computed. > > we now use p->se.sum_exec_runtime that measures (in nanoseconds) the > precise amount of time spent executing (sum of system and user time) - > and ->stime and ->utime is used to determine the 'split'. [this allows > us to gather ->stime and ->utime via low-resolution sampling, while > keeping the 'total' precise. Accounting at every system entry point > would be quite expensive on most platforms.] Using se.sum_exec_runtime to generate ->utime and ->stime breaks the process accounting we have on s390 (and probably on PowerPC too). With CONFIG_VIRT_CPU_ACCOUNTING we already have precise values in ->utime and ->stime. Can we make the calculation of the CFS-based time values conditional by CONFIG_VIRT_CPU_ACCOUNTING? Jan > Ingo > - > 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/