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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 904E0EB64DC for ; Fri, 14 Jul 2023 22:16:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229872AbjGNWQZ (ORCPT ); Fri, 14 Jul 2023 18:16:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56744 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229506AbjGNWQW (ORCPT ); Fri, 14 Jul 2023 18:16:22 -0400 Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 08CFA271E for ; Fri, 14 Jul 2023 15:16:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1689372981; x=1720908981; h=message-id:subject:from:to:cc:date:in-reply-to: references:content-transfer-encoding:mime-version; bh=GtF3KqbmiuznAQw7i6mlD0JBL433S/IryUTjVz3mHKY=; b=WBSCp3e+FalKUxTLZPKEvYk49qaVGsOghzoqWDWWMBi4m8YsljjpRUSP Yx8BM3kyscfhVzsENHyqfAlokHTkA/S1EmlKLFti5XfDFfLqGgkV+6hZX Q7hQHg97NZXEaa6lxsiylgcIo3ut6MdQuEhgIPSO6tn63V/zq2oZ1En0h aqUB0kOGT9H9ef3LiF+7bMrHM+VHlhmgxZqvamYY2H9+KlFWvgVLSJRYX 7f0oXjTWSENA7scPc8C+NXM13lArKs3IuX0QiiIosB2+3YfYGkFWcCH14 /1t6E9VYRa6c4K7oDdOSGP9znYB4FrAY8xzG9LL4xP0A8J3yEopW888hW Q==; X-IronPort-AV: E=McAfee;i="6600,9927,10771"; a="355527427" X-IronPort-AV: E=Sophos;i="6.01,206,1684825200"; d="scan'208";a="355527427" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Jul 2023 15:16:20 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10771"; a="787973268" X-IronPort-AV: E=Sophos;i="6.01,206,1684825200"; d="scan'208";a="787973268" Received: from bmuller-mobl.amr.corp.intel.com (HELO [10.209.37.94]) ([10.209.37.94]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Jul 2023 15:16:19 -0700 Message-ID: <5dbc278117107bcc4047dc55f783dad397da1704.camel@linux.intel.com> Subject: Re: [Patch v3 4/6] sched/fair: Consider the idle state of the whole core for load balance From: Tim Chen To: Shrikanth Hegde Cc: Ricardo Neri , Juri Lelli , Vincent Guittot , Ricardo Neri , "Ravi V . Shankar" , Ben Segall , Daniel Bristot de Oliveira , Dietmar Eggemann , Len Brown , Mel Gorman , "Rafael J . Wysocki" , Srinivas Pandruvada , Steven Rostedt , Valentin Schneider , Ionela Voinescu , x86@kernel.org, linux-kernel@vger.kernel.org, Srikar Dronamraju , naveen.n.rao@linux.vnet.ibm.com, Yicong Yang , Barry Song , Chen Yu , Hillf Danton , Peter Zijlstra Date: Fri, 14 Jul 2023 15:16:18 -0700 In-Reply-To: <29f8bc23-9b17-0a21-baa5-3eee1322f8f0@linux.vnet.ibm.com> References: <807bdd05331378ea3bf5956bda87ded1036ba769.1688770494.git.tim.c.chen@linux.intel.com> <29f8bc23-9b17-0a21-baa5-3eee1322f8f0@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.44.4 (3.44.4-2.fc36) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2023-07-14 at 18:32 +0530, Shrikanth Hegde wrote: >=20 >=20 >=20 > Tried on a symmetric system with all cores having SMT=3D4 as well. There = was reduction in migrations here as well. > Didnt observe any major regressions when microbenchmarks run alone. Such = as hackbench, stress-ng.=20 >=20 > So. Here is tested-by.=20 > Tested-by: Shrikanth Hegde Thanks for testing. =20 >=20 >=20 > > + > > /* Are we the first CPU of this group ? */ > > return group_balance_cpu(sg) =3D=3D env->dst_cpu; > > } >=20 > One doubt though, Here a fully idle core would be chosen instead of first= idle cpu in the=20 > group (if there is one). Since coming out of idle of SMT is faster compar= ed to a fully idle core, > would latency increase? Or that concerns mainly wakeup path? Yeah, I think that concern is for the wakeup path and not for the balance p= ath. Tim