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[66.183.142.209]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2ad74f5db00sm46193655ad.23.2026.02.21.14.51.45 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sat, 21 Feb 2026 14:51:45 -0800 (PST) From: "Doug Smythies" To: "'Peter Zijlstra'" , "'K Prateek Nayak'" Cc: "'Vincent Guittot'" , , , , , , , , , , , "Doug Smythies" References: <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> <20260212193140.GR1395266@noisy.programming.kicks-ass.net> <27217771-325a-4545-8a12-80dc6ff5112f@amd.com> <20260213064423.GB3088714@noisy.programming.kicks-ass.net> <20260213105020.GB3031506@noisy.programming.kicks-ass.net> <005e01dc9d7b$823100a0$869301e0$@telus.net> In-Reply-To: <005e01dc9d7b$823100a0$869301e0$@telus.net> Subject: RE: [PATCH 0/4] sched: Various reweight_entity() fixes Date: Sat, 21 Feb 2026 14:51:47 -0800 Message-ID: <000901dca384$a928dbb0$fb7a9310$@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 Thread-Index: AQJtnXszg5njiwQkFy3gQRLwpFHE4gLQF0cZAn1/j6ECG89NlwJg6Xg9ASX7x8wCCagYwAK4gyxmAix95woBwZMQwAMDUiVSArlm1QWzoN/1oA== Content-Language: en-ca On 2026.02.13 22:31 Doug Smythies wrote: > On 2026.02.13 02:50 Peter Zijlstra wrote: >> On Fri, Feb 13, 2026 at 07:44:24AM +0100, Peter Zijlstra wrote: >>> As to wrapper, I just went through math64.h and it appears we have >>> div64_long() that might just DTRT, but I really need to go wake up >>> first. >>> >>> And as you noted, the current branch doesn't boot :/ No idea what I >>> messed up last night, but I did push without test building. I only >>> folded those two division fixed and figured what could possibly go wrong >>> :-) >> >> It's now got div64_long() throughout. >> >> I've build and booted each commit in a vm; build and booted the combined >> stack on 2 different physical machines and re-ran the various >> benchmarks. >> >> Works-for-me. > > Works for me also. > > Note: I am calling this "V5" (version 5). > > But: please consider if there is an issue or not with test 3 below, > mainly detailed in the attached graphs. ... snip ... > 3.) a ridiculous load. Each thread is 100% load, no sleep. 20,000 X yes: > Conclusion: Pass? > Observation: The spin out rate of tasks is "clunky" not smooth. It used to be smooth. > A couple of graphs are attached. Note that actual sample times are now used, > after a nominal sleep of 2 seconds between samples. Sometimes the actual > gap is over 1 minute. It takes considerably longer, 2,200 seconds verses > 1,309 seconds to spin out the 20,000 takes for V5 verses kernel 6.19-rc8. Just a follow up: The above reported concern with this test never had anything to do with this patch series. It had everything to do with commit 7dadeaa6e851: sched: Further restrict the preemption modes and my use of the Ubuntu kernel configuration. In the header of the commit it says: While Lazy has been the recommended setting for a while, not all distributions have managed to make the switch yet. Force things along. The kernel configuration was automatically modified eliminating PREEMPT_VOLUNTARY and leaving PREEMPT_LAZY disabled. Once I set PREEMPT_LAZY the above noted concern was gone (although I am still testing). References: https://lore.kernel.org/all/20251219101502.GB1132199@noisy.programming.kicks-ass.net/