Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752934AbZGYFFA (ORCPT ); Sat, 25 Jul 2009 01:05:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751904AbZGYFFA (ORCPT ); Sat, 25 Jul 2009 01:05:00 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:42741 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751212AbZGYFE7 (ORCPT ); Sat, 25 Jul 2009 01:04:59 -0400 Date: Fri, 24 Jul 2009 22:04:23 -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: <20090724220423.11828b85.akpm@linux-foundation.org> In-Reply-To: <4A6A8E96.7050509@linux.intel.com> References: <4A64B813.1080506@linux.intel.com> <20090724212220.afa278ee.akpm@linux-foundation.org> <4A6A8AFE.1010608@linux.intel.com> <20090724214006.7380c3b4.akpm@linux-foundation.org> <4A6A8E96.7050509@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: 2718 Lines: 60 On Fri, 24 Jul 2009 21:48:22 -0700 Arjan van de Ven wrote: > Andrew Morton wrote: > > 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. > > looks like it does.. to bad we don't expose that data in a /proc//delay or something field > like we do with the scheduler info... > I thought we did deliver a few of the taskstats counters via procfs, but maybe I dreamed it. It would have been a rather bad thing to do. taskstats has a large advantage over /proc-based things: it delivers a packet to the monitoring process(es) when the monitored task exits. So with no polling at all it is possible to gather all that information about the just-completed task. This isn't possible with /proc. There's a patch on the list now to teach taskstats to emit a packet at fork- and exit-time too. The monitored task can be polled at any time during its execution also, like /proc files. Please consider switching whatever-you're-working-on over to use taskstats rather than adding (duplicative) things to /proc (which require CONFIG_SCHED_DEBUG, btw). If there's stuff missing from taskstats then we can add it - it's versioned and upgradeable and is a better interface. It's better to make taskstats stronger than it is to add /proc/pid fields, methinks. -- 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/