From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7D265ECE58C for ; Mon, 7 Oct 2019 15:14:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5E6932070B for ; Mon, 7 Oct 2019 15:14:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728170AbfJGPOU (ORCPT ); Mon, 7 Oct 2019 11:14:20 -0400 Received: from shelob.surriel.com ([96.67.55.147]:38058 "EHLO shelob.surriel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727711AbfJGPOT (ORCPT ); Mon, 7 Oct 2019 11:14:19 -0400 Received: from imladris.surriel.com ([96.67.55.152]) by shelob.surriel.com with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.92.3) (envelope-from ) id 1iHUi5-0008Tu-LJ; Mon, 07 Oct 2019 11:14:05 -0400 Message-ID: Subject: Re: [PATCH v3 09/10] sched/fair: use load instead of runnable load in wakeup path From: Rik van Riel To: Vincent Guittot , linux-kernel@vger.kernel.org, mingo@redhat.com, peterz@infradead.org Cc: pauld@redhat.com, valentin.schneider@arm.com, srikar@linux.vnet.ibm.com, quentin.perret@arm.com, dietmar.eggemann@arm.com, Morten.Rasmussen@arm.com, hdanton@sina.com Date: Mon, 07 Oct 2019 11:14:05 -0400 In-Reply-To: <1568878421-12301-10-git-send-email-vincent.guittot@linaro.org> References: <1568878421-12301-1-git-send-email-vincent.guittot@linaro.org> <1568878421-12301-10-git-send-email-vincent.guittot@linaro.org> Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="=-WuD0OLaHXmYk47Pie627" User-Agent: Evolution 3.30.5 (3.30.5-1.fc29) MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=-WuD0OLaHXmYk47Pie627 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2019-09-19 at 09:33 +0200, Vincent Guittot wrote: > runnable load has been introduced to take into account the case where > blocked load biases the wake up path which may end to select an > overloaded > CPU with a large number of runnable tasks instead of an underutilized > CPU with a huge blocked load. >=20 > Tha wake up path now starts to looks for idle CPUs before comparing > runnable load and it's worth aligning the wake up path with the > load_balance. >=20 > Signed-off-by: Vincent Guittot On a single socket system, patches 9 & 10 have the result of driving a woken up task (when wake_wide is true) to the CPU core with the lowest blocked load, even when there is an idle core the task could run on right now. With the whole series applied, I see a 1-2% regression in CPU use due to that issue. With only patches 1-8 applied, I see a 1% improvement in CPU use for that same workload. Given that it looks like select_idle_sibling and find_idlest_group_cpu do roughly the same thing, I wonder if it is enough to simply add an additional test to find_idlest_group to have it return the LLC sg, if it is called on the LLC sd on a single socket system. That way find_idlest_group_cpu can still find an idle core like it does today. Does that seem like a reasonable thing? I can run tests with that :) --=20 All Rights Reversed. --=-WuD0OLaHXmYk47Pie627 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- iQEzBAABCAAdFiEEKR73pCCtJ5Xj3yADznnekoTE3oMFAl2bVj0ACgkQznnekoTE 3oNkvAf9EIx4XCf3dXuBIbnv/VDATAw7RpjAhjca32QZlF2v2HCNkxQsuEWAaPBr t7grHeoD5jQIvyMulh2+uUJMZylURuPNdDs6+OyF3pHRSGNTMKhPkNGQVlwTmuvf GHayc0dHmYN/LjzcIGGdKYUnte7laSweKFGckYwSBnCLGwZyNNsIFJVIoohiqrRJ zf3LlBGrx0HisQdrywzdSJmXQVhCknycNU9N4zhUQkOBShY2r+a/2Q6xXFiw8Nuk oK0WKqbk09Erqy3sazKJpYy/Lgnf8ji/wT32OO+rwbf/i4RJYcLakSccooyNxdVm Gb24a8dg/MIyUfUn/vetydJrMNjtwQ== =rSUF -----END PGP SIGNATURE----- --=-WuD0OLaHXmYk47Pie627--