From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 CB9C630BB8C for ; Thu, 19 Feb 2026 14:56:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771512994; cv=none; b=b/rsLmq8ZrBxIMSGg58JJJ05yO6McCpkoGInVH+vtzYqZ55I1mQQS5guleMATbS49/4BFCZPj9SfNV1hbIA7G8MR1gOdcDia09NaNE1cogvs3I4o+FcCRZV7qXqKYxQpLxkZKg4X1M/IlhFnA3iJknJhg0vtLY8DKW7GyemdVxM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771512994; c=relaxed/simple; bh=+R3Snf51UQPz8HdzI10L6/vCNCw/Vynm2tO6Et1mDJE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=soknOfQeYGAcz+eYZPdeeGfWUoXwY2vqqAkx3lco9v0+DZHzRO64d3N3ByvRIzJ3i7DNM+tIzK9dD0yjhLfy3o+NHKV6XaK4h40snseBFUPRIU8mXEEe09i2kmcU1odogZzf79o3wR5a/9jMKLpdB6lVFWVnW1qC7xlKsacIUJw= 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=BeKTisgb; arc=none smtp.client-ip=90.155.92.199 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="BeKTisgb" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; 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=8YSoPL9OCRAaiORAH+Yk7WitBTFTvMnc3CvNqK8CQEA=; b=BeKTisgbiBXDEOY/1wjFouyOQu nwQqUkQhSX3IKKSRv1QcIpMxY+Cy6NIiVhK4ocA17JAwQu6VDLOzONV+NXEktpF28NIDqIlTqapfU lFJVsgklWzL/YElKWtCDQA2yYZ8jAVsixY1smvoUlg89tcNRDLvu+W1Mj6WHTesky+/H3xdK0lG3s kDzFng5mOBYhpbN/N5JTXLIOEUIcbMlzcKtBvMA5iVtqgOkAmDS6GOyMRFDPNjmXsY3sviUggqbKL ib31gxOlNgyrU2IEcOA7ZtXsgr8jtyypwblyCdmMj8FKIN5C3ocxi6+Q8m9YuM0Hne9rSxOd1TUO+ pO+AQTVw==; Received: from 2001-1c00-8d85-5700-266e-96ff-fe07-7dcc.cable.dynamic.v6.ziggo.nl ([2001:1c00:8d85:5700:266e:96ff:fe07:7dcc] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1vt5Rc-00000001P2M-2Itl; Thu, 19 Feb 2026 14:55:58 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 1604C30075B; Thu, 19 Feb 2026 15:55:56 +0100 (CET) Date: Thu, 19 Feb 2026 15:55:56 +0100 From: Peter Zijlstra To: "Chen, Yu C" Cc: Tim Chen , Ingo Molnar , K Prateek Nayak , "Gautham R . Shenoy" , Vincent Guittot , Juri Lelli , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Madadi Vineeth Reddy , Hillf Danton , Shrikanth Hegde , Jianyong Wu , Yangyu Chen , Tingyin Duan , Vern Hao , Vern Hao , Len Brown , Aubrey Li , Zhao Liu , Chen Yu , Adam Li , Aaron Lu , Tim Chen , Josh Don , Gavin Guo , Qais Yousef , Libo Chen , linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 03/21] sched/cache: Introduce helper functions to enforce LLC migration policy Message-ID: <20260219145556.GJ1282955@noisy.programming.kicks-ass.net> References: <7475922f6020abe5d458a136b0c88fe24e823091.1770760558.git.tim.c.chen@linux.intel.com> <20260219112911.GF1395266@noisy.programming.kicks-ass.net> 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: On Thu, Feb 19, 2026 at 10:48:11PM +0800, Chen, Yu C wrote: > Hi Peter, > > On 2/19/2026 7:29 PM, Peter Zijlstra wrote: > > On Tue, Feb 10, 2026 at 02:18:43PM -0800, Tim Chen wrote: > > > > > +/* > > > + * The margin used when comparing utilization. > > > + * is 'util1' noticeably greater than 'util2' > > > + * Derived from capacity_greater(). > > > + * Bias is in perentage. > > > + */ > > > +/* Allows dst util to be bigger than src util by up to bias percent */ > > > +#define util_greater(util1, util2) \ > > > + ((util1) * 100 > (util2) * 120) > > > > > + * 20% is the utilization imbalance percentage to decide > > > + * if the preferred LLC is busier than the non-preferred LLC. > > > + * 20 is a little higher than the LLC domain's imbalance_pct > > > + * 17. The hysteresis is used to avoid task bouncing between the > > > + * preferred LLC and the non-preferred LLC. > > > > So not saying this needs changing now, but consider that imbalance_pct > > can be changed through debugfs. Do you want this 120 to be expressed in > > terms of imbalance_pct rather than being hardcoded? > > Got it, I will look into adding a margin to imbalance_pct for this > comparison. With this change, I assume we can remove the llc_imb_pct > debugfs entry in patch 19. I hadn't gotten that far yet. Still trying to read patch 4 :-)