From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id EF22934D381 for ; Thu, 30 Oct 2025 20:53:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761857637; cv=none; b=NGxXQDkRlB13bo3faqJyUI2HKEqnbPabe52qE36rEdN93Npad1yYYyoFfFQxpg4Wmtszs7DTeb7xsbk41Ui2ZH719gpFOUV6kzQzokOFVNwp3ZdMumEPzpniZ7yTK3AwceI3nWFGQyhvaMEb08HomWGKGlVTFQTPOjpmd2SOPkM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761857637; c=relaxed/simple; bh=4UUILT+XE/ynC6tQo7M7UBDDdRiufVw1/KI8YewZb/c=; h=Message-ID:Date:MIME-Version:From:Subject:To:Cc:References: In-Reply-To:Content-Type; b=TJrESRSory0ElNGqCjKIdLXRvufarXX49x/mGaf0tTh9yWpq/d7UTiw/GiXcQD1j0qaattzrpIOGZzChfz+sq4W3RHDrxPob8bB4yhURKe4bfozEyn2VWkvfZKOglQOdBEzDFJr+A5bvdMRxnDZg1cxUMe1kjO2jwFvbIdLAnac= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 41D882C40; Thu, 30 Oct 2025 13:53:46 -0700 (PDT) Received: from [10.57.85.174] (unknown [10.57.85.174]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 026463F66E; Thu, 30 Oct 2025 13:53:51 -0700 (PDT) Message-ID: Date: Thu, 30 Oct 2025 21:53:50 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Dietmar Eggemann Subject: Re: [External] : Re: [REGRESSION][v6.17-rc1]sched/fair: Bump sd->max_newidle_lb_cost when newidle balance fails To: Peter Zijlstra , Adam Li Cc: Joseph Salisbury , Chris Mason , clm@fb.com, Vincent Guittot , Juri Lelli , Ingo Molnar , Steven Rostedt , bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, LKML References: <006c9df2-b691-47f1-82e6-e233c3f91faf@oracle.com> <28340138-a00e-47bc-a36f-270a01ac83b4@meta.com> <20251007113459.GF3245006@noisy.programming.kicks-ass.net> <36545e62-9947-43ef-9bc1-776f5663a45c@oracle.com> <20251010170937.GG4067720@noisy.programming.kicks-ass.net> <2aa7380b-bebd-4bb9-8597-49e06d1dcc6d@os.amperecomputing.com> <20251030093013.GI4067720@noisy.programming.kicks-ass.net> Content-Language: en-GB In-Reply-To: <20251030093013.GI4067720@noisy.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 30.10.25 10:30, Peter Zijlstra wrote: > > Hi Adam, > > On Thu, Oct 30, 2025 at 03:22:34PM +0800, Adam Li wrote: > >> Commit 155213a2aed4 brings ~6% regression for SpecJBB critical-jOPS on >> AmpereOne server. >> >> Baseline: v6.17 kernel + patch. Compared with baseline: >> NI_TARGET +7% >> NI_SPARE -3% >> NI_RUNNABLE -4% >> NI_RANDOM -3% >> >> So NI_TARGET reverts the performance regression. >> The other options brings more regression for SpecJBB. > > Excellent, how does NI_TARGET+NI_RANDOM work for you? Like Chris, I > found that the schbench workload was really suffering from doing too > many idle balance attempts that weren't really working out. > > NI_RANDOM reduces the number of newidle balances based on the success > ratio. Eg. if you have successful balancing 25% of the time, it will do > 1 in 4 balances and count a successful balance as 4 to keep the > accounting straight. > > So workloads with a high success rate will keep newidle balance calls > frequent, while workloads with a low success rate (like schbench) will > greatly reduce the number of calls. Results with OLTP 'hammerdb - mysqld' on Arm64 VMs NOPM P50 latency 6.18-rc3 baseline baseline 6.18-rc3-revert-155213a2aed4 +12% -8.5% 6.18-rc3 NI_TARGET +12% -8.2% 6.18-rc3 NI_SPARE +-0% +-0% 6.18-rc3 NI_RUNNABLE -1% +1% 6.18-rc3 NI_RANDOM -1% +1% Looks like only NI_TARGET reverts the regression here.