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[66.183.142.209]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-824c6a431f2sm33525b3a.22.2026.02.12.11.37.57 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 12 Feb 2026 11:37:58 -0800 (PST) From: "Doug Smythies" To: "'Peter Zijlstra'" , "'K Prateek Nayak'" Cc: "'Vincent Guittot'" , , , , , , , , , , , "Doug Smythies" 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> <20260212192911.GM1395416@noisy.programming.kicks-ass.net> In-Reply-To: <20260212192911.GM1395416@noisy.programming.kicks-ass.net> Subject: RE: [PATCH 0/4] sched: Various reweight_entity() fixes Date: Thu, 12 Feb 2026 11:37:59 -0800 Message-ID: <003101dc9c57$185e3ff0$491abfd0$@telus.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-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 16.0 Content-Language: en-ca Thread-Index: AQMWYubz/xEMVhBSz3apzpK2ovtIkQGuW2zjAlK+Dh4A5A0FgwJtnXszAtAXRxkCfX+PoQIbz02XAmDpeD0BJfvHzAHX8GtlsmsPDVA= On 2026.02.12 11:29 Peter Zijlstra wrote: > 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. I got to the full 20,000 X yes tasks on my test computer. All good.