Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751653AbZGYEkY (ORCPT ); Sat, 25 Jul 2009 00:40:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751372AbZGYEkY (ORCPT ); Sat, 25 Jul 2009 00:40:24 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:40765 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751367AbZGYEkX (ORCPT ); Sat, 25 Jul 2009 00:40:23 -0400 Date: Fri, 24 Jul 2009 21:40:06 -0700 From: Andrew Morton To: Arjan van de Ven Cc: Linux Kernel Mailing List , Ingo Molnar , Peter Zijlstra , "Kok, Auke-jan H" Subject: Re: [PATCH] sched: Provide iowait counters Message-Id: <20090724214006.7380c3b4.akpm@linux-foundation.org> In-Reply-To: <4A6A8AFE.1010608@linux.intel.com> References: <4A64B813.1080506@linux.intel.com> <20090724212220.afa278ee.akpm@linux-foundation.org> <4A6A8AFE.1010608@linux.intel.com> X-Mailer: Sylpheed 2.4.8 (GTK+ 2.12.5; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1435 Lines: 34 On Fri, 24 Jul 2009 21:33:02 -0700 Arjan van de Ven wrote: > Andrew Morton wrote: > > On Mon, 20 Jul 2009 11:31:47 -0700 Arjan van de Ven wrote: > > > >> For counting how long an application has been waiting for (disk) IO, > >> there currently is only the HZ sample driven information available, while > >> for all other counters in this class, a high resolution version is > >> available via CONFIG_SCHEDSTATS. > >> > >> In order to make an improved bootchart tool possible, we also need > >> a higher resolution version of the iowait time. > >> > >> This patch below adds this scheduler statistic to the kernel. > > > > Doesn't this duplicate the delay accounting already available via the > > taskstats interface? > > we have how long we wait. we do not have how long we iowait afaik... > at least not in nanosecond granularity. (We do have the sampled data, but that > is milisecond sampled data, not very useful for making charts based on time > to show the sequence of events) See include/linux/sched.h's definition of task_delay_info - u64 blkio_delay is in nanoseconds. It uses do_posix_clock_monotonic_gettime() internally. -- 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/