From: Peter Zijlstra <peterz@infradead.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Juri Lelli <juri.lelli@redhat.com>,
mingo@redhat.com, vincent.guittot@linaro.org,
linux-kernel@vger.kernel.org, tglx@kernel.org, will@kernel.org,
boqun@kernel.org, dietmar.eggemann@arm.com, rostedt@goodmis.org,
bsegall@google.com, mgorman@suse.de, vschneid@redhat.com,
kprateek.nayak@amd.com, luca.abeni@santannapisa.it,
mathieu.poirier@linaro.org, longman@redhat.com,
ridong.chen@linux.dev, tj@kernel.org, hannes@cmpxchg.org,
mkoutny@suse.com, shuah@kernel.org, bigeasy@linutronix.de,
clrkwllms@kernel.org, parri.andrea@gmail.com,
m.szyprowski@samsung.com, kayracizmeci@gmail.com,
weihengqiuu@gmail.com, cgroups@vger.kernel.org,
linux-kselftest@vger.kernel.org, linux-rt-devel@lists.linux.dev,
stable@vger.kernel.org
Subject: Re: [PATCH v5 13/29] sched/deadline: Keep departing bandwidth across a root domain rebuild
Date: Wed, 11 Nov 2026 17:19:12 +0100 [thread overview]
Message-ID: <20261111161912.GP1779021@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <c3e7054a-486c-4e5a-a646-eee42e815ce4@efficios.com>
On Wed, Nov 11, 2026 at 10:35:17AM -0500, Mathieu Desnoyers wrote:
> Measured in a 64-vCPU guest with sleeping deadline tasks:
>
> tasks today: rebuild, longest irqs-off single list, all irqs-off
> 1000 0.75ms, under 0.1ms 0.12ms (0.19ms worst)
> 10000 7.4ms, under 0.1ms (0.3ms once) 0.9ms (1.2ms worst)
>
> The rebuild itself is 8 times shorter. That comes from updating the
> extra_bw of the CPUs once per root domain, not once per task. But the
> longest section with interrupts disabled grows with the number of
> deadline tasks. I do not think that is a step forward for a real-time
> class.
This is domain rebuild? Do we really care about performance there?
next prev parent reply other threads:[~2026-11-11 16:19 UTC|newest]
Thread overview: 66+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-08 18:53 [PATCH v5 00/29] sched/deadline: bandwidth accounting fixes and selftests Mathieu Desnoyers
2026-11-08 18:53 ` [PATCH v5 01/29] sched: Fix cpuset_mutex double unlock in __sched_setscheduler() Mathieu Desnoyers
2026-11-08 18:53 ` [PATCH v5 02/29] sched: Refuse SCHED_FLAG_KEEP_PARAMS that would change the policy or the class Mathieu Desnoyers
2026-11-08 18:53 ` [PATCH v5 03/29] sched/deadline: Do not admit bandwidth for parameters that are kept Mathieu Desnoyers
2026-11-09 12:42 ` Juri Lelli
2026-11-09 13:16 ` Mathieu Desnoyers
2026-11-08 18:53 ` [PATCH v5 04/29] sched: Let a task boosted by a deadline waiter change its policy Mathieu Desnoyers
2026-11-09 13:38 ` Juri Lelli
2026-11-08 18:53 ` [PATCH v5 05/29] sched/deadline: Do not divide by zero active CPUs of a root domain Mathieu Desnoyers
2026-11-09 14:30 ` Juri Lelli
2026-11-09 14:57 ` Mathieu Desnoyers
2026-11-09 15:09 ` Juri Lelli
2026-11-09 15:22 ` Mathieu Desnoyers
2026-11-08 18:53 ` [PATCH v5 06/29] sched: Take cpuset_mutex for a deadline policy change only with pi Mathieu Desnoyers
2026-11-09 15:06 ` Juri Lelli
2026-11-09 15:22 ` Mathieu Desnoyers
2026-11-08 18:53 ` [PATCH v5 07/29] sched/deadline: Do not lose a throttled task switched out and back Mathieu Desnoyers
2026-11-09 16:05 ` Juri Lelli
2026-11-09 16:29 ` Mathieu Desnoyers
2026-11-09 18:55 ` Mathieu Desnoyers
2026-11-09 18:56 ` Mathieu Desnoyers
2026-11-08 18:53 ` [PATCH v5 08/29] sched/deadline: Take a deadline boost from the waiter's rt_mutex node Mathieu Desnoyers
2026-11-10 11:14 ` Juri Lelli
2026-11-10 13:48 ` Mathieu Desnoyers
2026-11-08 18:53 ` [PATCH v5 09/29] sched/deadline: Reset the deadline and the runtime with the parameters Mathieu Desnoyers
2026-11-10 13:18 ` Juri Lelli
2026-11-10 13:41 ` Mathieu Desnoyers
2026-11-08 18:53 ` [PATCH v5 10/29] sched/deadline: Reset the donor's runtime at a deboost in the class Mathieu Desnoyers
2026-11-08 19:17 ` sashiko-bot
2026-11-09 2:56 ` Mathieu Desnoyers
2026-11-08 18:53 ` [PATCH v5 11/29] sched/deadline: Release the bandwidth of a task that leaves the class asleep Mathieu Desnoyers
2026-11-10 19:47 ` Juri Lelli
2026-11-10 20:26 ` Mathieu Desnoyers
2026-11-08 18:53 ` [PATCH v5 12/29] sched/deadline: Reject SCHED_DEADLINE on exited tasks Mathieu Desnoyers
2026-11-11 6:55 ` Juri Lelli
2026-11-08 18:53 ` [PATCH v5 13/29] sched/deadline: Keep departing bandwidth across a root domain rebuild Mathieu Desnoyers
2026-11-11 12:59 ` Juri Lelli
2026-11-11 15:35 ` Mathieu Desnoyers
2026-11-11 16:19 ` Peter Zijlstra [this message]
2026-11-08 18:53 ` [PATCH v5 14/29] sched/deadline: Fix this_bw when a task is changed during a remote wakeup Mathieu Desnoyers
2026-11-11 13:49 ` Juri Lelli
2026-11-08 18:53 ` [PATCH v5 15/29] sched/deadline: Rebuild the root domains' accounting from the task list Mathieu Desnoyers
2026-11-11 14:24 ` Juri Lelli
2026-11-08 18:53 ` [PATCH v5 16/29] sched/deadline: Record the root domain holding a task's bandwidth Mathieu Desnoyers
2026-11-11 15:54 ` Juri Lelli
2026-11-08 18:53 ` [PATCH v5 17/29] sched/deadline: Leave a dying task out of a rebuild of the accounting Mathieu Desnoyers
2026-11-08 18:53 ` [PATCH v5 18/29] sched/deadline: Move a task's bandwidth only where room was made Mathieu Desnoyers
2026-11-08 19:30 ` sashiko-bot
2026-11-09 2:57 ` Mathieu Desnoyers
2026-11-08 18:53 ` [PATCH v5 19/29] cgroup/cpuset: Wait for an attach before rebuilding the sched domains Mathieu Desnoyers
2026-11-08 18:53 ` [PATCH v5 20/29] cgroup/cpuset: Give back the bandwidth an attach did not move Mathieu Desnoyers
2026-11-08 18:53 ` [PATCH v5 21/29] cgroup/cpuset: Reserve the bandwidth in the root domain a task moves to Mathieu Desnoyers
2026-11-08 19:32 ` sashiko-bot
2026-11-09 2:57 ` Mathieu Desnoyers
2026-11-08 18:53 ` [PATCH v5 22/29] sched/deadline: Make a rebuild use the CPU recorded with a task's bandwidth Mathieu Desnoyers
2026-11-08 19:25 ` sashiko-bot
2026-11-09 2:58 ` Mathieu Desnoyers
2026-11-08 18:54 ` [PATCH v5 23/29] sched/deadline: Move a task's bandwidth when it must leave its CPU Mathieu Desnoyers
2026-11-08 19:41 ` sashiko-bot
2026-11-09 2:58 ` Mathieu Desnoyers
2026-11-08 18:54 ` [PATCH v5 24/29] sched/deadline: Cancel the replenishment timer with the parameters Mathieu Desnoyers
2026-11-08 18:54 ` [PATCH v5 25/29] sched/deadline: Count the bandwidth a boosted task is given Mathieu Desnoyers
2026-11-08 18:54 ` [PATCH v5 26/29] sched/debug: Show the deadline bandwidth of each runqueue Mathieu Desnoyers
2026-11-08 18:54 ` [PATCH v5 27/29] selftests/sched: Add a test of SCHED_DEADLINE policy round trips Mathieu Desnoyers
2026-11-08 18:54 ` [PATCH v5 28/29] selftests/sched: Test SCHED_DEADLINE bandwidth across a root domain rebuild Mathieu Desnoyers
2026-11-08 18:54 ` [PATCH v5 29/29] selftests/sched: Add a test of SCHED_DEADLINE bandwidth accounting Mathieu Desnoyers
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