Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933042AbaFCPuY (ORCPT ); Tue, 3 Jun 2014 11:50:24 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:56462 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932172AbaFCPuX (ORCPT ); Tue, 3 Jun 2014 11:50:23 -0400 Date: Tue, 3 Jun 2014 17:50:07 +0200 From: Peter Zijlstra To: Morten Rasmussen Cc: Vincent Guittot , "mingo@kernel.org" , "linux-kernel@vger.kernel.org" , "linux@arm.linux.org.uk" , "linux-arm-kernel@lists.infradead.org" , "preeti@linux.vnet.ibm.com" , "efault@gmx.de" , "nicolas.pitre@linaro.org" , "linaro-kernel@lists.linaro.org" , "daniel.lezcano@linaro.org" Subject: Re: [PATCH v2 08/11] sched: get CPU's activity statistic Message-ID: <20140603155007.GZ30445@twins.programming.kicks-ass.net> References: <1400860385-14555-1-git-send-email-vincent.guittot@linaro.org> <1400860385-14555-9-git-send-email-vincent.guittot@linaro.org> <20140528121001.GI19967@e103034-lin> <20140528154703.GJ19967@e103034-lin> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="jBytRjlvjIVQOM9g" Content-Disposition: inline In-Reply-To: <20140528154703.GJ19967@e103034-lin> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --jBytRjlvjIVQOM9g Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, May 28, 2014 at 04:47:03PM +0100, Morten Rasmussen wrote: > Since we may do periodic load-balance every 10 ms or so, we will perform > a number of load-balances where runnable_avg_sum will mostly be > reflecting the state of the world before a change (new task queued or > moved a task to a different cpu). If you had have two tasks continuously > on one cpu and your other cpu is idle, and you move one of the tasks to > the other cpu, runnable_avg_sum will remain unchanged, 47742, on the > first cpu while it starts from 0 on the other one. 10 ms later it will > have increased a bit, 32 ms later it will be 47742/2, and 345 ms later > it reaches 47742. In the mean time the cpu doesn't appear fully utilized > and we might decide to put more tasks on it because we don't know if > runnable_avg_sum represents a partially utilized cpu (for example a 50% > task) or if it will continue to rise and eventually get to 47742. Ah, no, since we track per task, and update the per-cpu ones when we migrate tasks, the per-cpu values should be instantly updated. If we were to increase per task storage, we might as well also track running_avg not only runnable_avg. --jBytRjlvjIVQOM9g Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJTje6vAAoJEHZH4aRLwOS6kEMQAInvizNLVoAp0DllUcRnWCcd tZE1iuOh0eaDDUwHPMZMi0Ki9hK4kHkFoFTa8RyeYJ2beUe7i3SDcx87ceUCr54o q2dc/lIeyERngVsLunb3gqmLKnFzmSRAQ7h+k5FmoZgZ9usvyU9bmTuYh5jJLGGt 3AxFoM8yJehKFK/GyM6ykvPYduzbLmTKjUfPLNZSWMcT6s9L1tmz3P4qmyOmsUN9 6q75w3v6Pf6/McfcPsG3ghLeGopyj+jxUGBORyHkH0l9DOcaC5W/Z1i7V1CTASFs sNOzklIaZdLa3VikiF+jmMhhUcunIeeL+t9nHQwKRd6jIcKnF21OXe9VTHEoswB9 ALIeRcagERXS7V2P/MINPqXlSLOlOiI3XV9QAsb1U8R5JgSVgtpBB1IBbcNnRC4Z hL/PTYdGVHz6fxo/GXpLUAf6DwMykmPkkdROPt4NxKQg4Vr4bZIdPWZIdvlRFS3l i/dVCEBFv050Dzc/N1lAz/uUW2puYjKuR+c7tIoZusucHT1jcT5Suntkn8nY36zn Lsy6VOJ+TRHLXiR30LcBoTP+gfo4GQF2PFHMf66qP0Tpbxze7SeC3JJt5lFfOh9K +5CLwzgA4Gc1rQIHSq3RoXIsIzdXn1FwPEDw3vnUryv1wfBDpBkIQ3RIe1e4lsPk ENnkRsxSNq5FNmRXOdTU =rT1E -----END PGP SIGNATURE----- --jBytRjlvjIVQOM9g-- -- 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/