From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=90.155.50.34 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793354201; b=WxumnVjAF9xX5qt4iJtmOc0DKL4QWAnMurVq6n6M3m225JOb6CiBnPGGq35/leOi5jP1 RMWiUPn3IEj9E5Frpkakg8z1KI7F5lw1T8UFU6BMX8EPFrZUqfER9vspIWFps5lJHGGno XtpJLk2wH++OKFs8YwYcFJbNTxjfnYcrVGsFmcjNVJrkrIpQHdOEiEhT80JfnyhoHko+7 lOTKiLCz6SaXtnPBATs9MzMA4v4qxHi2sSkRJZm3pV9k5TBVi7wWVgzCbEE1ialNvwMtr JMMKMB8QOx7EO/EevgDsDWQFWqaAOl+ONJ6/gaSJHJjSnrCeRnA+oupNat2/nTFNiHA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793354201; h=DMARC-Filter:DKIM-Signature:Received:Received:Date:From:To:Cc: Subject:Message-ID:References:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; bh=5xiejaFvgYu1bZJnBCs0ytrTR8vL1a3ZrRscchf483o=; b=lpT8iaEkQwTDBAcKgFs3Z6GCesrnykzNQWTf/umQWY2h0lSxjirx7cYuxchgw9zms2Ol kZmiMPpz873VQszIkGzeSnRqDS3NmMB4kYeerT038Emebg8Ji7rTyQ9yZgqOLAyF2lKdw Zfdnn6Htzrxm/+HMctyEY7+SBPVyMNKbusyXhFEbQW8p3VgYA/lO1I6rub0AF03pGiTZq +CwfzMos+NkLiwEkb3DAhQgAsATQIRBsdyWLXMk5mKLDuD2k2svMlSd3qrB91HLfZxW7G Pc2LN0AswcHwD+3DmBMPj2WDP9xSZ2vTm1qCSK/a/UJBnZ2Jaby+znInp1n3gGadEng== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass header.d=infradead.org header.i=@infradead.org header.a=rsa-sha256 header.s=casper.20170209 header.b="Ywe4/hep"; arc=none smtp.remote-ip=90.155.50.34 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BE581606A325 for ; Fri, 30 Oct 2026 09:56:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org BE581606A325 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=infradead.org header.i=@infradead.org header.a=rsa-sha256 header.s=casper.20170209 header.b=Ywe4/hep 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=5xiejaFvgYu1bZJnBCs0ytrTR8vL1a3ZrRscchf483o=; b=Ywe4/hepCn13MWag7VEpyxVe9S RqxxW31FBFOdjP/8Eu2Tg50YiAPYoJcg0s8JjmsDF7x2OrVcVYKjmTwfZILGw2gsEZPIijr5LYT9H FO2HzY/l3NMlc+y5ZpMHUDreYQ//VrdSUe7LYsvZ4goxgUCiqubAzxDoic09em32Xx4+EMoQvRQ8+ qp+Xo7Ofi1FWyJpLz3qoWIowc5GSfMCPXGNi27u5zg8FwbIXDwU50HAdsi/k/RErtpZ/pyWvq2RD6 kIK8pljsGNxJvSPOqi0iXz5o48Jme4nWQ2ZxyDa3zqwwueZ/C4luYaPhtGYUU12HTuXl+l3JLpj9O 3nVuYqcA==; 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 4.100.1 #2 (Red Hat Linux)) id 1xMjLb-00000004pKS-1YHe; Fri, 30 Oct 2026 09:56:31 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 61736300329; Fri, 30 Oct 2026 10:56:30 +0100 (CET) Date: Fri, 30 Oct 2026 10:56:30 +0100 From: Peter Zijlstra To: K Prateek Nayak Cc: Qing Wang , Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Tim Chen , Chen Yu , Davi Chaves Azevedo , linux-kernel@vger.kernel.org Subject: Re: [PATCH v4] sched/fair: Replace random newidle_balance with Bresenham accumulator Message-ID: <20261030095630.GJ2668200@noisy.programming.kicks-ass.net> References: <20261030091946.2498870-1-wangqing7171@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Oct 30, 2026 at 03:16:13PM +0530, K Prateek Nayak wrote: > Hello Qing, > > On 10/30/2026 2:49 PM, Qing Wang wrote: > > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > > index 919d0fb00bd9..79c477b47510 100644 > > --- a/kernel/sched/topology.c > > +++ b/kernel/sched/topology.c > > @@ -2002,6 +2002,7 @@ sd_init(struct sched_domain_topology_level *tl, > > .newidle_call = 512, > > .newidle_success = 256, > > .newidle_ratio = 512, > > + .newidle_window_pos = 0, > > nit. > > I think this value should start in a way that allows newidle balance to run at > first attempt and then stabilize. Maybe '512; is a good number if not higher? Funnily enough, treating this as an independent variable and using a random number works and 'fixes' the slope change problems.