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Date:   Wed, 8 Nov 2023 14:46:21 +0100
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Subject: Re: [PATCH v5 6/7] sched/deadline: Deferrable dl server
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Daniel Bristot de Oliveira <bristot@redhat.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Joel Fernandes <joel@joelfernandes.org>,
        Ingo Molnar <mingo@redhat.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
        Valentin Schneider <vschneid@redhat.com>,
        linux-kernel@vger.kernel.org,
        Luca Abeni <luca.abeni@santannapisa.it>,
        Tommaso Cucinotta <tommaso.cucinotta@santannapisa.it>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vineeth Pillai <vineeth@bitbyteword.org>,
        Shuah Khan <skhan@linuxfoundation.org>,
        Phil Auld <pauld@redhat.com>
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From:   Daniel Bristot de Oliveira <bristot@kernel.org>
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On 11/8/23 13:44, Peter Zijlstra wrote:
> Because the above also causes period drift, which we do not want.

The period drift is not a problem when we do not have DL tasks because
... we do not have dl tasks. The task will run for runtime.

But not doing the period drift is bad if we have DL tasks because we
break the (current u <= U) rule... which breaks CBS/EDF.