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 D02FE3B14C6; Tue, 29 Sep 2026 08:17:44 +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=1790669866; cv=none; b=elr44AqLh0HHkGqQAVRLieHw0p8rA9kaTW99JXQF7YMppPTJlkJz1j9shiVDIXBeDBtfqeTrLYWcdkVJk8zjtbWotobCL7WKClCZTDNAH6OXbk5BQFWb7cmYYgSrDjaBPiQc6RU8MTNJYrBMh4zr7UbmgKYieOoG0iG5y08fGfk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790669866; c=relaxed/simple; bh=9wjlQLssATALYhKM0vpkOIcxvVmpWm1aP34WbYkqIbA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=si2yRm+bBLDzbtSQ+HJ05kKPKp15td+NFtEJmxaoO8Yb9mM4INNml1UTJrnFc034lBcHwzZMbv3z2b97pVOFarxMefBnooUEsP7dmKq13T+43V61VhKAtlqcfY/i+7YvWmrLKnIRP1QYoqutj6/OM6bgh9CZbPxeeAM1oWJ8Rhk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=Gqu8QVk2; 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=pass 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="Gqu8QVk2" 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=9wjlQLssATALYhKM0vpkOIcxvVmpWm1aP34WbYkqIbA=; b=Gqu8QVk2WonuQBpb3WMf8KpX+O Chm2ExLDnu2QFPuHjF/UvhHPx3UELfAtyslk5+0jGYtS214mFRSRRArDi4fgGeavZ2J4Gpl/dZXlD eVVX58Z0/Pj3IIBYJOozGJgLeZX+P1vATGJHmoPHqn4wVbDCHOfHEanDimsxiUjNYUl/Ig5XBKBG8 T+4WV588I3cxM9iEwUP4Vw89thBVugIlBc6XIU3n1E4gR8aQfyQAYxaWGZaTSn6Oq+xWMFi7n4mT1 cIJyJH0vjUWC6ekkTvsgFnM2ZOG/3x6ZOo2DwiPHHBUcwKIT+MEuOi9bJKRSvaZ6UYJpzb7yTsVd0 SEcp4dPw==; 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 4.99.1 #2 (Red Hat Linux)) id 1xBT1x-0000000BgJe-2Nsd; Tue, 29 Sep 2026 08:17:41 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id B9C95300446; Tue, 29 Sep 2026 10:17:40 +0200 (CEST) Date: Tue, 29 Sep 2026 10:17:40 +0200 From: Peter Zijlstra To: David Stevens Cc: Johannes Weiner , Suren Baghdasaryan , Ingo Molnar , K Prateek Nayak , linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] sched/psi: clamp negative cpu_clock() skew Message-ID: <20260929081740.GH4121620@noisy.programming.kicks-ass.net> References: <20260928233743.3777102-1-stevensd@google.com> <20260929081004.GS4120091@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: <20260929081004.GS4120091@noisy.programming.kicks-ass.net> On Tue, Sep 29, 2026 at 10:10:04AM +0200, Peter Zijlstra wrote: > > When running browser workloads on an Intel N100 with a sustained > > psi.mem.some of 2-3%, this underflow is observed once every couple of > > hours. Reading is hard. This is sad, that's a relatively modern chip :-(