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 43EAA39B486 for ; Mon, 30 Mar 2026 19:43:32 +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=1774899813; cv=none; b=kWdG6FQRlVdm5qydAyeCdGKvGN8469bWJsf/q47E/5SOD+RKT1aQH+1m/nLyO8YP3oxoA2eiEh/oFrSjoSDddEz0mUTSdN5rtxIdNroCpJRSGIf8ZnfZnIRgVVggNw2l/nXWBLLb9B7H6SXlNhHrgE5Ct03mcQ3pdNTYDAM6hJw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774899813; c=relaxed/simple; bh=dn5foIfIZ199ysk2mgT8xi0wFLAhL/w6wro+WMrJYjA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=NcTbGP6oFCNjHaFgjr1dtfJ2H+vwvNvYn+YQvmLDb+bmnM2nrey2t2RuaAtYJKqd+GUgVZdl3OWB5u2AiBcQvxyWysiAsKMzvFGMNL45y7GCi6ZHbs9IzvSItl7ei8rQEOejzVj2aPyWhiAOiXH0qHPj8KHuD7Y4RhvUnMRE6qI= 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=VSaU5kDG; 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="VSaU5kDG" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Transfer-Encoding: Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=aJEvwisu0ElX2eJVTvjTF3v65JCYWr7H5oD8k2XLz9g=; b=VSaU5kDGoyUZm07MIBrHBu+fUq GUlQLoQOw7oympQqs5IMeuZn8QXrj2+PAIoILyD2UadiebWuTesnih4kZl9evcv5obG5PxcWrKPnR CviRSmx0UNzIQCpE3XWTHobBlhgCbF28byZLWtOI/q5cNu1nMTxCR0O7/aAN7wD6d4zFvFgtUn3iQ PApcvt2Xy6qqQT3wl92QTZ+bcDnmcRDNt+9nVG4219gUYO4VStkuqZjV6B8lg4js50QFNjuwudZQp 1Zag9KwZDsnDnLfndGOL5Dcr4fx4sv4+nWD6SUrN+mcjQjqTT/A5NZ8J9TC1SSKQOB3N7SlsNemNp 9azTy2mg==; Received: from 2001-1c00-8d85-4b00-266e-96ff-fe07-7dcc.cable.dynamic.v6.ziggo.nl ([2001:1c00:8d85:4b00:266e:96ff:fe07:7dcc] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1w7IW3-0000000EcIp-39EB; Mon, 30 Mar 2026 19:43:15 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id A28E130057E; Mon, 30 Mar 2026 21:43:14 +0200 (CEST) Date: Mon, 30 Mar 2026 21:43:14 +0200 From: Peter Zijlstra To: John Stultz Cc: mingo@kernel.org, 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, wangtao554@huawei.com, quzicheng@huawei.com, kprateek.nayak@amd.com, dsmythies@telus.net, shubhang@os.amperecomputing.com, Suleiman Souhlal Subject: Re: [PATCH v2 1/7] sched/fair: Fix zero_vruntime tracking Message-ID: <20260330194314.GV2872@noisy.programming.kicks-ass.net> References: <20260219075840.162631716@infradead.org> <20260219080624.438854780@infradead.org> <20260330101018.GN3738786@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=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Mon, Mar 30, 2026 at 12:40:45PM -0700, John Stultz wrote: > On Mon, Mar 30, 2026 at 3:10 AM Peter Zijlstra wrote: > > This means, that if the two tasks playing leapfrog can reach the > > critical speed to reach the overflow point inside one tick's worth of > > time, we're up a creek. > > > > If this is indeed the case, then the below should cure things. > > > > This also means that running a HZ=100 config will increase the chances > > of hitting this vs HZ=1000. > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > index 9298f49f842c..c7daaf941b26 100644 > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -9307,6 +9307,7 @@ static void yield_task_fair(struct rq *rq) > > if (entity_eligible(cfs_rq, se)) { > > se->vruntime = se->deadline; > > se->deadline += calc_delta_fair(se->slice, se); > > + avg_vruntime(cfs_rq); > > } > > } > > I just tested with this and similar to Prateek, I also still tripped the issue. > > I'll give your new patch a spin here in a second. Stick both on please :-) AFAICT they're both real, just not convinced they're what you're hitting.