Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757626Ab2EHW3v (ORCPT ); Tue, 8 May 2012 18:29:51 -0400 Received: from merlin.infradead.org ([205.233.59.134]:59578 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754975Ab2EHW3u convert rfc822-to-8bit (ORCPT ); Tue, 8 May 2012 18:29:50 -0400 Message-ID: <1336516174.8226.59.camel@twins> Subject: RE: [PATCH] sched: Make nr_uninterruptible count a signed value From: Peter Zijlstra To: Diwakar Tundlam Cc: "'Ingo Molnar'" , "'David Rientjes'" , "'linux-kernel@vger.kernel.org'" , Peter De Schrijver Date: Wed, 09 May 2012 00:29:34 +0200 In-Reply-To: <1336516020.8226.57.camel@twins> References: <1DD7BFEDD3147247B1355BEFEFE46652379C3DF10C@HQMAIL04.nvidia.com> <1336514192.8226.52.camel@twins> <1DD7BFEDD3147247B1355BEFEFE46652379C3DF10D@HQMAIL04.nvidia.com> <1336516020.8226.57.camel@twins> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT X-Mailer: Evolution 3.2.2- Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2740 Lines: 68 On Wed, 2012-05-09 at 00:27 +0200, Peter Zijlstra wrote: > On Tue, 2012-05-08 at 15:14 -0700, Diwakar Tundlam wrote: > > Sorry to bug you when it is late for you.. > > > Nah, I'm the idiot still behind the screen after midnight, its just the > brain that's slightly slower and needs more hints. > > > You're right, there is no real difference at all. > > Only cosmetic difference when you look at the output of > > cat /proc/sched_debug. > > Not sure I see that.. the printf is still using %Ld (signed) so the > output shouldn't matter regardless of if the variable is unsigned long > or long. > > > > But I suddenly realized maybe the increment/decrement of > > nr_interruptible is reversed. > > Maybe that's the source of the problem: decrement in activate task and > > increment in deactivate task !! > > No that's right. nr_uninterruptible counts the number of tasks in > uninterruptible sleep, so deactivate_task puts a task to sleep, so we > need to increment the number of sleeping tasks, activate_task wakes a > task up so we need to decrement the number of sleeping tasks. > > I think the problem you're having is that we don't match the cpu where > we inc and dec the counter, and that's fully on purpose since its rather > expensive -- it would require atomics. > FWIW the way to properly read the sched_debug output is something like: # grep nr_uninterruptible /proc/sched_debug .nr_uninterruptible : -1305 .nr_uninterruptible : 336 .nr_uninterruptible : -229 .nr_uninterruptible : 276 .nr_uninterruptible : 105 .nr_uninterruptible : 157 .nr_uninterruptible : -2782 .nr_uninterruptible : 325 .nr_uninterruptible : -471 .nr_uninterruptible : 9 .nr_uninterruptible : 205 .nr_uninterruptible : 88 .nr_uninterruptible : 7 .nr_uninterruptible : 912 .nr_uninterruptible : 188 .nr_uninterruptible : 66 .nr_uninterruptible : 87 .nr_uninterruptible : 45 .nr_uninterruptible : 194 .nr_uninterruptible : 1178 .nr_uninterruptible : 185 .nr_uninterruptible : 143 .nr_uninterruptible : 136 .nr_uninterruptible : 145 # awk '/nr_uninterruptible/ {t += $3} END {print t}' /proc/sched_debug 0 The per-cpu value is meaningless, only the sum over all cpus is a meaningful number. -- 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/