From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EC9D11FDA7B for ; Fri, 25 Apr 2025 17:29:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.17 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745602199; cv=none; b=E4O6clZLNPTwgwGwYjcAmKBaR+Pql5PVDwne3Py3GJlUpMhBfO8wCiv5FaR59dcLujqSIMFjQq+zSysMjSMW4c8in9hzp4ucIe2zCAk3YyzJgTPHJocrS8TFMG+fXgbUcIkIUm2LlStFkdqLDqjBq9DVnId6vDMHqtvO8Ifo7qw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745602199; c=relaxed/simple; bh=mOhJxojf3lQ5fZ7xRz363WxEzooIgLk4ZEwnmCjzat0=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=Or8pRY5Ttz3v/z0IBDJxZgJDjW95fvDaYcTgGOtY5Ssls4A9xQKHI06JQWiZ54Nsb9VUEiehs5MVqJA66xgES3a+ecdp3C2LdKtE4vmP1cSHpcCQyI8jZID8VAFwV/5Ilq5l2RswN6Vw72wnvO3t0Z6YOl51D9tz5KudJGUYaYQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=none smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=Nrg7KigP; arc=none smtp.client-ip=192.198.163.17 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="Nrg7KigP" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1745602198; x=1777138198; h=message-id:subject:from:to:cc:date:in-reply-to: references:content-transfer-encoding:mime-version; bh=mOhJxojf3lQ5fZ7xRz363WxEzooIgLk4ZEwnmCjzat0=; b=Nrg7KigPdDWUc8SaLEKmlysqIesGAmbo2hxu98MyE/mZTZhmXrS7PbBd ufIHiO+oE4Skrl54lMSPPuTn0h5jpFw1DymZs4u+8nO+bN91tUUkgFViu rYq+NVogzqkFEISNhonGgqJJwYFfWb15YTtd93dXEBB7eLZFSESk59Eq/ P56sGDg5fMxFcvDhzyBLY8nY5vaU6tSxV4BxeGHuWacLSKbTsV7ZrwwWV SOVwK69Y4bLjmDUWhNrDnUEUhaCgyM2gWdkszGZBbHUB3/iY2zS+fdQAK QCpVQWQge+19I/qi0al3Von8zx4h8NDC24mScH8YHOxWCtNTpa/IgozUU A==; X-CSE-ConnectionGUID: nRVUWaG8T4uV9iDLhaxkTA== X-CSE-MsgGUID: mIUtvMztQmaUhXpTo74Yew== X-IronPort-AV: E=McAfee;i="6700,10204,11414"; a="47146382" X-IronPort-AV: E=Sophos;i="6.15,238,1739865600"; d="scan'208";a="47146382" Received: from orviesa001.jf.intel.com ([10.64.159.141]) by fmvoesa111.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Apr 2025 10:29:56 -0700 X-CSE-ConnectionGUID: d6X29c6STEGiIVQzz9+I/w== X-CSE-MsgGUID: NAsZJXKuTOaBcVHfi2zG5Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.15,238,1739865600"; d="scan'208";a="170172027" Received: from spandruv-desk1.amr.corp.intel.com (HELO [10.125.108.233]) ([10.125.108.233]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Apr 2025 10:29:55 -0700 Message-ID: <0a574da2c69e6bd607e20c5865d3b66fb9329e6d.camel@linux.intel.com> Subject: Re: [RFC PATCH 4/5] sched: Inhibit cache aware scheduling if the preferred LLC is over aggregated From: Tim Chen To: e45141a1a64d7dcfca2683f56735ba4da60ba19e.camel@linux.intel.com Cc: "Chen, Yu C" , Peter Zijlstra , Ingo Molnar , K Prateek Nayak , "Gautham R . Shenoy" , Juri Lelli , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Tim Chen , Vincent Guittot , Libo Chen , Abel Wu , Hillf Danton , linux-kernel@vger.kernel.org, Len Brown , Chen Yu , Madadi Vineeth Reddy Date: Fri, 25 Apr 2025 10:29:55 -0700 In-Reply-To: References: <2c45f6db1efef84c6c1ed514a8d24a9bc4a2ca4b.1745199017.git.yu.c.chen@intel.com> Autocrypt: addr=tim.c.chen@linux.intel.com; prefer-encrypt=mutual; keydata=mQENBE6N6zwBCADFoM9QBP6fLqfYine5oPRtaUK2xQavcYT34CBnjTlhbvEVMTPlNNzE5v04Kagcvg5wYcGwr3gO8PcEKieftO+XrzAmR1t3PKxlMT1bsQdTOhKeziZxh23N+kmA7sO/jnu/X2AnfSBBw89VGLN5fw9DpjvU4681lTCjcMgY9KuqaC/6sMbAp8uzdlue7KEl3/D3mzsSl85S9Mk8KTLMLb01ILVisM6z4Ns/X0BajqdD0IEQ8vLdHODHuDMwV3veAfnK5G7zPYbQUsK4+te32ruooQFWd/iqRf815j6/sFXNVP/GY4EWT08UB129Kzcxgj2TEixe675Nr/hKTUVKM/NrABEBAAGJAS4EIAECABgFAk6ONYoRHQFLZXkgaXMgcmVwbGFjZWQACgkQHH3vaoxLv2UmbAgAsqa+EKk2yrDc1dEXbZBBGeCiVPXkP7iajI/FiMVZHFQpme4vpntWhg0BIKnF0OSyv0wgn3wzBWx0Zh3cve/PICIj268QvXkb0ykVcIoRnWwBeavO4dd304Mzhz5fBzJwjYx06oabgUmeGawVCEq7UfXy+PsdQdoTabsuD1jq0MbOL/4sB6CZc4V2mQbW4+Js670/sAZSMj0SQzK9CQyQdg6Wivz8GgTBjWwWsfMt4g2u0s6rtBo8NUZG/yw6fNdaoDaT/OCHuBopGmsmFXInigwOXsjyp15Yqs/de3S2Nu5NdjJUwmN1Qd1bXEc/ItvnrFB0RgoNt2gzf25aPifLabQlVGltIENoZW4gPHRpbS5jLmNoZW5AbGludXguaW50ZWwuY29tPokBOAQTAQIAIgUCTo3rPAIbAwYLCQgHAwIGFQgCCQoLBBYCAwECHgECF4AACgkQHH3vaoxLv2XYdAf8DgRO4eIAtWZy4zLv0EZHWiJ35GYAQ5fPFWBoNURE0+vICrvLyfCKTlUTFxFxTiAWHUO7JM+uBHQSJVsE+ERmTPsiU 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 iQFUBBMBCAA+FiEEEsKdz9s94XWwiuG96lQbuGeTCYsFAlwLCmACGwMFCQHhM4AFCwkIBwIGFQoJCAsCBBYCAwECHgECF4AACgkQ6lQbuGeTCYuQiQf9G2lkrkRdLjXehwCl+k5zBkn8MfUPi2ItU2QDcBit/YyaZpNlSuh8h30gihp5Dlb9BnqBVKxooeIVKSKC1HFeG0AE28TvgCgEK8qP/LXaSzGvnudek2zxWtcsomqUftUWKvoDRi1AAWrPQmviNGZ4caMd4itKWf1sxzuH1qF5+me6eFaqhbIg4k+6C5fk3oDBhg0zr0gLm5GRxK/lJtTNGpwsSwIJLtTI3zEdmNjW8bb/XKszf1ufy19maGXB3h6tA9TTHOFnktmDoWJCq9/OgQS0s2D7W7f/Pw3sKQghazRy9NqeMbRfHrLq27+Eb3Nt5PyiQuTE8JeAima7w98quQ== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.4 (3.50.4-1.fc39) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2025-04-25 at 14:43 +0530, Madadi Vineeth Reddy wrote: > Hi Tim, >=20 > On 24/04/25 21:21, Tim Chen wrote: > > On Thu, 2025-04-24 at 22:11 +0800, Chen, Yu C wrote: > > >=20 > > > > It spawns lot of threads and is CPU intensive. So, I think it's not= impacted > > > > due to the below conditions. > > > >=20 > > > > Also, in schbench numbers provided by you, there is a degradation i= n saturated > > > > case. Is it due to the overhead in computing the preferred llc whic= h is not > > > > being used due to below conditions? > > >=20 > > > Yes, the overhead of preferred LLC calculation could be one part, and= we=20 > > > also suspect that the degradation might be tied to the task migration= s.=20 > > > We still observed more task migrations than the baseline, even when t= he=20 > > > system was saturated (in theory, after 25% is exceeded, we should=20 > > > fallback to the generic task wakeup path). We haven't dug into that y= et,=20 > > > and we can conduct an investigation in the following days. > >=20 > > In the saturation case it is mostly the tail latency that has regressio= n. > > The preferred LLC has a tendency to have higher load than the > > other LLCs. Load balancer will try to move tasks out and wake balance w= ill > > try to move it back to the preferred LLC. This increases the task migra= tions > > and affect tail latency. >=20 > Why would the task be moved back to the preferred LLC in wakeup path for = the > saturated case? The checks shouldn't allow it right? The task wake ups happens very frequently in schbench and it takes a while = for utilization to catch up. The utilization of the LLC is updated at the load balance time of LLC.= =C2=A0 So once utilization falls below the utilization threshold, there is a windo= w where the woken tasks will rush into the preferred LLC until the utilizatio= n is updated at the next load balance time.=20 Tim >=20 > Thanks, > Madadi Vineeth Reddy >=20 > >=20 > > Tim >=20