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 980A53090C9 for ; Fri, 14 Nov 2025 09:37:23 +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=1763113046; cv=none; b=gMUxPdT0yv8P7UINOoVifvyfnDkD2lLBaP2OPed0OU6nggbeSSab+pt/ZAX55SxaM2rZ8Jy1ZFjIHaOAHjOUmfdxqU1J92Z4RP/KLQe0oyN3SR0HGz1ynVS8f3ADjgdlP0nI4NDYxgD/Kb+d0QC/AOf5KOpAqHsY6syg8TAjTtU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763113046; c=relaxed/simple; bh=YqRw82S7CeRJ/GVX2OtllCRdMrD7nzc6PJvEGSBERn0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ZF8akNTtW8L8aMgY1NEWlZmJnCQ7t9OwBTjQvRUOsf698ACAFZ3ACta8hl/Al1z60871A4Uxzj1l5MAy0jfXFkLnvEZRKwaMFNxoxV1x636stOVC6fMJZ9EUovHixu60tMR2bu2cZ2Czfq7UdSwjG+deU6BkPsTONVTzd0zh27g= 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=f9/57t7j; 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="f9/57t7j" 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=V4YT3VWOpECNLH09iSo6LzGszIyUhL/7oaZZNgPowuo=; b=f9/57t7jo2MuCvh9Gqs3YBFtTB xlkGd9LJscR76zNcG+cYiZXKSyZeDVz2pXNgR/3Ehe2nmlGmJvJPWF0rri9ROJe9TzOxgZfXHqK/K MTHIsBvkLKxrRybJDyvaht+/lF+v0FD6djBXjYRqP80z1S+j9r9siJl+UOIiIjb+/tkbThuRNUYZG 8wb6watPt0RbDWPoW9RW6egGDXluPhtFYuKEtvKX79CJjvCrxn1qj0Un18cZtpLcbAQfBli7t9u/O DyAjBig7Ei7aMCfmXiBQECn37/5kn/0GFXv2vjMlcuwUH+mWGz+N89hlH91KLSnWXUl8HgcAdegTC pK/QyRRw==; 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 1vJqEy-000000093Lf-327D; Fri, 14 Nov 2025 09:37:12 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 8BD4D30023C; Fri, 14 Nov 2025 10:37:11 +0100 (CET) Date: Fri, 14 Nov 2025 10:37:11 +0100 From: Peter Zijlstra To: Chris Mason Cc: Joseph Salisbury , Adam Li , Hazem Mohamed Abuelfotoh , Josh Don , mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/4] sched: The newidle balance regression Message-ID: <20251114093711.GG3245006@noisy.programming.kicks-ass.net> References: <20251107160645.929564468@infradead.org> <6825c50d-7fa7-45d8-9b81-c6e7e25738e2@meta.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: <6825c50d-7fa7-45d8-9b81-c6e7e25738e2@meta.com> On Wed, Nov 12, 2025 at 04:59:45PM -0500, Chris Mason wrote: > On 11/7/25 11:06 AM, Peter Zijlstra wrote: > > Hi! > > > > So most of you ran into Chris' commit 155213a2aed4 ("sched/fair: Bump > > sd->max_newidle_lb_cost when newidle balance fails") [*] > > > > And I posted a patch with a few alternative options. And while I've heard back > > from a number of you, indicating that NI_TARGET (the effective revert) works > > for you. Not many tested TARGET+RANDOM (thanks Adam!). > > > > In my limited schbench testing that combination isn't horrible, and per Adam > > that combination also doesn't suck for him. Chris, could you please see what > > this does for your machines with your actual workload? > > > > Anyway, here are a few patches that basically do the revert and introduce the > > proportional newidle balance -- the NI_TARGET+NI_RANDOM equivalent. > > > > Also at: > > > > git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git sched/newidle > > > > Please all, give it a whirl. Hopefully I didn't wreck it, its Friday after all :-) > > > > [*] https://lkml.kernel.org/r/006c9df2-b691-47f1-82e6-e233c3f91faf@oracle.com > > This is working well for my original benchmark. Focusing on newidle > balance schedstat counters (10 second interval): > > Linus: > lb_balance_newly_idle 22854 > > Mason-revert: > lb_balance_newly_idle 2334059 > > Peter: > lb_balance_newly_idle 75271 > > The rest of the schbench numbers look good too. Sweet!