linux-kernel - Re: [PATCH v5 6/7] sched/deadline: Deferrable dl server

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Message-ID: <20231107143216.170ca582@gandalf.local.home>
Date:   Tue, 7 Nov 2023 14:32:16 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Joel Fernandes <joel@...lfernandes.org>
Cc:     Daniel Bristot de Oliveira <bristot@...nel.org>,
        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>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        linux-kernel@...r.kernel.org,
        Luca Abeni <luca.abeni@...tannapisa.it>,
        Tommaso Cucinotta <tommaso.cucinotta@...tannapisa.it>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vineeth Pillai <vineeth@...byteword.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Phil Auld <pauld@...hat.com>
Subject: Re: [PATCH v5 6/7] sched/deadline: Deferrable dl server



Just got this too (with the 20% we talked about on IRC).

 migrate-991     6.....   713.996237: print:                tracing_mark_write: thread 7 iter 3 sleeping

The above is 991 in userspace writing to trace_marker

 migrate-991     6d..2.   713.996251: bprint:               __schedule: Pick userspin:973:120

I added the above printk in the core pick_next_task().

 migrate-991     6d..2.   713.996254: sched_switch:         migrate:991 [90] S ==> userspin:973 [120]

We switch to userspin for just 16 microseconds, and notice, NEED_RESCHED is
not set.

userspin-973     6dN.2.   713.996270: bprint:               pick_task_rt: Pick RT migrate:988:93

The above printk is in pick_next_task_rt(), and NEED_RESCHED is now set!

userspin-973     6dN.2.   713.996271: bprint:               __schedule: Pick migrate:988:93
userspin-973     6d..2.   713.996272: sched_switch:         userspin:973 [120] R ==> migrate:988 [93]

I'll add your latest patch and see if that's different.

I'll also test this without any of the patches first.

-- Steve