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dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=efficios.com; Received: from YT6PR01MB491026.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b01:1d0::10) by YT3PR01MB179232.CANPRD01.PROD.OUTLOOK.COM (2603:10b6:b00:113::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.592.10; Thu, 5 Nov 2026 19:11:19 +0000 Received: from YT6PR01MB491026.CANPRD01.PROD.OUTLOOK.COM ([fe80::6b9e:a901:67c5:7ddc]) by YT6PR01MB491026.CANPRD01.PROD.OUTLOOK.COM ([fe80::6b9e:a901:67c5:7ddc%6]) with mapi id 15.21.0592.009; Thu, 5 Nov 2026 19:11:19 +0000 Message-ID: <49685618-a72a-41e6-a191-f30b61b2afe8@efficios.com> Date: Thu, 5 Nov 2026 14:11:18 -0500 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 09/21] sched/deadline: Keep departing bandwidth across a root domain rebuild To: sashiko-reviews@lists.linux.dev Cc: linux-rt-devel@lists.linux.dev, tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com, linux-kernel@vger.kernel.org References: <20261104211207.1392343-1-mathieu.desnoyers@efficios.com> <20261104211207.1392343-10-mathieu.desnoyers@efficios.com> From: Mathieu Desnoyers Content-Language: en-US In-Reply-To: Content-Type: text/plain; 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A departed task boosted into the class before its 0-lag time is counted once, wherever a rebuild runs: the walk finds it in the class and counts it in its cpuset's root domain, the record is updated, and the release at the deboost reads the record. Where the deboost races the walk, the departing bandwidth is dropped for the remaining lag, as it is for a departed task whose recorded CPU went inactive; the generation keeps the release out, so nothing underflows. The release before the 0-lag time of a task boosted and deboosted while asleep, after leaving the class, is early by at most the lag, where the baseline leaked it for good. A rebuild that finds a CPU for a task an earlier one dropped counts it again, which is the intent: the bandwidth of a departed task is held until its 0-lag time. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com