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 3B7F61643B for ; Thu, 12 Feb 2026 19:29:29 +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=1770924572; cv=none; b=UnJV8uOfUoPrKTTrH0VO+VvfIL54JHMZpmKvvMWNS9za7BP4FAHjcTI2E5no7NxaOjRx2oAxYZ3949bEGNnHY5U7YVio5eA3QbQxC517cyFRHqtf2GJwMQ7vOpLmR6TxlpiiSqNuHXyVWU13aWuDgYEf9DwbiEDS0RlfTMZMZfU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770924572; c=relaxed/simple; bh=3OIo/fO3FWHaLtWFmx0pdaintmT2HTpWmOhBEQchUT4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Etv5LAWEhvbfPomTIgPaMtEquMAXlf6fH4DTkmkCxv4HiWbgY6RaApkeDAJWjmgWliQ3UGK6d+C+0QwLOy4wTmaDPq7v+meRCGoff/MFJgln7O3GLw7fKLKL5oc+eBrEtIBQXCL1rchemVgF3TvtfnmT+jql64oStuyTnLucxVA= 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=vA+Q/Nkn; 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="vA+Q/Nkn" 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=IX3cJPVQzQhDgTJqV6PtuiXzaVCi1r3EUyM9w4wdgk8=; b=vA+Q/NknY6kJqY1sorrETL6koI 660RUBegVfjD+hGbmpizXJyRbV0YWxlwWKBF1TM9AJcfde6C5TWnkUB3AGmzRmcDAcwQ4vfy1hdWC DCRhslVRZOF3D9mGz1+xelwjN3SF5cABgryUN7V/5dJXsmV6Do/66YYOdwuEki4OgnX9ykBKtLctK rTtk9fhC20RedNtV6e018+1dGY464CboaLjUmkhwVzD4FUJknAHI3+jxXD5kPKGCN2ZRiPtV6uQSK LzkduI5KCWo49VqowDmIt/wN8/P4ULWQDjZDSbppLQnTuiPjJQdfB3Wfh7iy6a77Uwzzy9omuHr2Z EAv6JbgA==; 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 casper.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1vqcNE-0000000Ecpi-2hJw; Thu, 12 Feb 2026 19:29:12 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 720AF300754; Thu, 12 Feb 2026 20:29:11 +0100 (CET) Date: Thu, 12 Feb 2026 20:29:11 +0100 From: Peter Zijlstra To: K Prateek Nayak Cc: Vincent Guittot , Doug Smythies , mingo@kernel.org, juri.lelli@redhat.com, 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, wuyun.abel@bytedance.com Subject: Re: [PATCH 0/4] sched: Various reweight_entity() fixes Message-ID: <20260212192911.GM1395416@noisy.programming.kicks-ass.net> References: <002501dc9b16$442a7050$cc7f50f0$@telus.net> <20260211090144.GY1282955@noisy.programming.kicks-ass.net> <20260211104833.GH1395416@noisy.programming.kicks-ass.net> <20260211162825.GZ1282955@noisy.programming.kicks-ass.net> <58c6c115-f544-4c51-990c-a3ad2fbf701a@amd.com> <20260212115943.GB1282955@noisy.programming.kicks-ass.net> <20260212171611.GL1395416@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: <20260212171611.GL1395416@noisy.programming.kicks-ass.net> On Thu, Feb 12, 2026 at 06:16:11PM +0100, Peter Zijlstra wrote: > On Thu, Feb 12, 2026 at 12:59:43PM +0100, Peter Zijlstra wrote: > > On Thu, Feb 12, 2026 at 01:13:30PM +0530, K Prateek Nayak wrote: > > > > Enqueue cfs_rq: depth(1) weight(2144337920) nr_queued(2045) sum_w_vruntime(18343811230990336) sum_weight(2144337920) zero_vruntime(18337852274) sum_shift(0) avg_vruntime(18337852274) > > > Dequeue cfs_rq: depth(1) weight(2144337920) nr_queued(2045) sum_w_vruntime(1303379968) sum_weight(2143289344) zero_vruntime(18354971669) sum_shift(0) avg_vruntime(18354971669) > > After staring at waaay too many traces of my own, which confirm what > you're seeing, but didn't want to make any sense either... > > ... I thinks I found it ... > > Note that sum_weight, that has _just_ flipped bit 31 and thus turned > negative *if* it were a 32bit number. Every time, exactly at this point > things started to go sideways. > > So I went looking for where this might be and I found the below. > > My latest run has passed 0x8000000/(1024*1024) = 2048 tasks and is still > running. Numbers are still sane, fingers crossed. > I made it all the way to 3k tasks on the one CPU and all is well.