From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 E77BB341678 for ; Thu, 30 Oct 2025 09:30:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761816627; cv=none; b=Q018y5hNp47A08i2OGBz8y7wlqo0ADyO072NbYQonZ8Bg7QNYUUS5FH1uux35IemKQiPTQl8s7FnUMQ6EzXv2cgETGz83QOvJBYah2vI9lDHrp5Qw5HjV3DrYZlwd9EpFwNpM6WV0KjWr5+OpVG1bL5ldrepydRBey1QEcfcLmA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761816627; c=relaxed/simple; bh=5GlMRQtGH2G2gDAvQEsZfUFiG9JUxvh98BBVJOE8/lk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ubajCzO8gj0XOW3e/t7fQuqlU8TMP4Sch5wfWH7211uJn9pMb5p6ckLdzaSXBn0kpWQ1HxzK22PUI8KJDF6sRll3yDpN5lJuipczAkPmHD61XAKcpa0g/+M4PEry0Ao0t/0SO9T2BvDwz5cR/wxBbvBe9BAswRAAM0M4cJDz36Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=dInDxbEa; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="dInDxbEa" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=/nDypDsdSKuowBHLqpSMoZOwLxsLaOUn0lb2AWVf9v4=; b=dInDxbEasc+47t+VNB40tKpYzN iuLOWtWEL8L6MK17CVdNKcylRdnpzJWxidxy08xuuCjOJGHJsGFw4J+PDHZQ68uqSyR0Vq8xOOtq5 gfjYpFtuQieGBtigMfGBnq+QR7lK0a4av1P+H/2GmgcCa8kYRizhb26uSdqc6HGgwtS7UMN3+kWwM JmXZHPVwqtfnK/zsA+PRXNkpPpJ+cAlg0c7l88dz7K8DGlMLkGBDU5V2zs1j9FQk+EXnSUuINim3O d0TmyCvtUmXjHWS3G1HCwOpJ1+zJojQPGZij4qeAFNJW7c5DDu+QUQUtI/tfC5CK6S9KPgKH0+Exu FWPseAIg==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1vEOyz-00000001bSO-2QKR; Thu, 30 Oct 2025 09:30:14 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 4F2D630029E; Thu, 30 Oct 2025 10:30:13 +0100 (CET) Date: Thu, 30 Oct 2025 10:30:13 +0100 From: Peter Zijlstra To: Adam Li Cc: Joseph Salisbury , Chris Mason , clm@fb.com, Vincent Guittot , Juri Lelli , Ingo Molnar , dietmar.eggemann@arm.com, Steven Rostedt , bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, LKML Subject: Re: [External] : Re: [REGRESSION][v6.17-rc1]sched/fair: Bump sd->max_newidle_lb_cost when newidle balance fails Message-ID: <20251030093013.GI4067720@noisy.programming.kicks-ass.net> 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2aa7380b-bebd-4bb9-8597-49e06d1dcc6d@os.amperecomputing.com> 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.