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Thu, 05 Nov 2026 07:00:50 -0800 (PST) X-Received: by 2002:a05:600d:82e2:b0:4a1:c27d:e1a8 with SMTP id 5b1f17b1804b1-4b55d7d7a2amr55605885e9.10.1793890850041; Thu, 05 Nov 2026 07:00:50 -0800 (PST) Received: from jlelli-thinkpadt14gen4.remote.csb ([151.29.158.90]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4b452eb99b1sm108926575e9.3.2026.11.05.07.00.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 Nov 2026 07:00:48 -0800 (PST) Date: Thu, 5 Nov 2026 16:00:46 +0100 From: Juri Lelli To: Mathieu Desnoyers Cc: Peter Zijlstra , Ingo Molnar , Vincent Guittot , linux-kernel@vger.kernel.org, Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Luca Abeni , Mathieu Poirier , Waiman Long , Ridong Chen , Tejun Heo , Johannes Weiner , Michal =?iso-8859-1?Q?Koutn=FD?= , Shuah Khan , Sebastian Andrzej Siewior , Clark Williams , cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-rt-devel@lists.linux.dev Subject: Re: [PATCH v2 08/21] selftests/sched: Add a test of SCHED_DEADLINE policy round trips Message-ID: References: <20261104211207.1392343-1-mathieu.desnoyers@efficios.com> <20261104211207.1392343-9-mathieu.desnoyers@efficios.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261104211207.1392343-9-mathieu.desnoyers@efficios.com> Hello, On 04/11/26 16:11, Mathieu Desnoyers wrote: > Add deadline_switch_test, with a case for the fix two patches back and > one for commit 41a7968022ca ("sched/deadline: Fix total_bw leak when > switching away from SCHED_DEADLINE while !queued"): > > - throttled_round_trip: a task with a runtime of 10ms per 2s period > spins, so that each replenishment throttles it again at once. Right > after a throttle it is switched to SCHED_OTHER, and back 200us after > its deadline: past its replenishment timer, and before its 0-lag > time, which the overrun scaled by 200 puts later. It must run again > within a period and a half. Three attempts; > - asleep_round_trip: a task of 9ms every 10ms, running 0.2ms and > sleeping 50ms, is switched to SCHED_OTHER and back while it sleeps > past its 0-lag time, enough times that a leak of its bandwidth at > each round trip fills the root domain: sched_setattr() then fails > with EBUSY. Skipped without admission control (sched_rt_runtime_us > at -1). A kernel that leaks is left without SCHED_DEADLINE bandwidth > until a reboot, so this case runs last. > > In 8 VMs of 8 vCPUs each, v7.3 fails both cases, and v7.4-rc1 with the > four deadline fixes of sched/urgent fails the first; with the two > previous patches as well both pass; every time. > > Signed-off-by: Mathieu Desnoyers > --- Thanks for the selftests! Very useful. FWIW I did propose some already in the past, but then didn't get time/ tokens for a follow up: https://lore.kernel.org/all/20260306-upstream-deadline-kselftests-v1-0-2b23ef74c46a@redhat.com/ We can probably re-start the effort with yours and keep adding as needed. Do we want to have per-policy subdirs under sched? Thanks, Juri