linux-kernel - Re: [PATCH v5 00/14] Add a deadline server for sched

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Message-ID: <a8dc965c-94e8-4941-a292-f14eb76831d9@nvidia.com>
Date: Fri, 20 Jun 2025 16:44:54 -0400
From: Joel Fernandes <joelagnelf@...dia.com>
To: linux-kernel@...r.kernel.org
Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Juri Lelli <juri.lelli@...hat.com>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>,
 Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
 Mel Gorman <mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>,
 Tejun Heo <tj@...nel.org>, David Vernet <void@...ifault.com>,
 Andrea Righi <arighi@...dia.com>, Changwoo Min <changwoo@...lia.com>,
 bpf@...r.kernel.org
Subject: Re: [PATCH v5 00/14] Add a deadline server for sched_ext tasks



On 6/20/2025 4:32 PM, Joel Fernandes wrote:
> sched_ext tasks currently are starved by RT hoggers especially since RT
> throttling was replaced by deadline servers to boost only CFS tasks. Several
> users in the community have reported issues with RT stalling sched_ext tasks.
> Add a sched_ext deadline server as well so that sched_ext tasks are also
> boosted and do not suffer starvation.
> 
> A kselftest is also provided to verify the starvation issues are now fixed.
> 
> Btw, there is still something funky going on with CPU hotplug and the
> relinquish patch. Sometimes the sched_ext's hotplug self-test locks up
> (./runner -t hotplug). Reverting that patch fixes it, so I am suspecting
> something is off in dl_server_remove_params() when it is being called on
> offline CPUs.

Sorry that I forgot to delete this last paragraph. The hotplug issue is
completely fixed now (since v4).

There are no more open issues and all tests on mine and Andrea's side are
looking good now.

Thanks.