From: luca abeni <luca.abeni@santannapisa.it>
To: Juri Lelli <juri.lelli@redhat.com>
Cc: linux-kernel@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
"Rafael J . Wysocki" <rafael@kernel.org>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
"Paul E . McKenney" <paulmck@linux.ibm.com>,
Joel Fernandes <joel@joelfernandes.org>,
Quentin Perret <quentin.perret@arm.com>,
Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Daniel Bristot de Oliveira <bristot@redhat.com>,
Patrick Bellasi <patrick.bellasi@arm.com>,
Tommaso Cucinotta <tommaso.cucinotta@santannapisa.it>
Subject: Re: [RFC PATCH 4/6] sched/dl: Improve capacity-aware wakeup
Date: Wed, 8 May 2019 11:24:37 +0200 [thread overview]
Message-ID: <20190508112437.74661fa8@nowhere> (raw)
In-Reply-To: <20190508090855.GG6551@localhost.localdomain>
On Wed, 8 May 2019 11:08:55 +0200
Juri Lelli <juri.lelli@redhat.com> wrote:
> On 06/05/19 06:48, Luca Abeni wrote:
> > From: luca abeni <luca.abeni@santannapisa.it>
> >
> > Instead of considering the "static CPU bandwidth" allocated to
> > a SCHED_DEADLINE task (ratio between its maximum runtime and
> > reservation period), try to use the remaining runtime and time
> > to scheduling deadline.
> >
> > Signed-off-by: luca abeni <luca.abeni@santannapisa.it>
> > ---
> > kernel/sched/cpudeadline.c | 9 +++++++--
> > 1 file changed, 7 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
> > index d21f7905b9c1..111dd9ac837b 100644
> > --- a/kernel/sched/cpudeadline.c
> > +++ b/kernel/sched/cpudeadline.c
> > @@ -114,8 +114,13 @@ static inline int dl_task_fit(const struct
> > sched_dl_entity *dl_se, int cpu, u64 *c)
> > {
> > u64 cap = (arch_scale_cpu_capacity(NULL, cpu) *
> > arch_scale_freq_capacity(cpu)) >> SCHED_CAPACITY_SHIFT;
> > - s64 rel_deadline = dl_se->dl_deadline;
> > - u64 rem_runtime = dl_se->dl_runtime;
> > + s64 rel_deadline = dl_se->deadline -
> > sched_clock_cpu(smp_processor_id());
> > + u64 rem_runtime = dl_se->runtime;
> > +
> > + if ((rel_deadline < 0) || (rel_deadline *
> > dl_se->dl_runtime < dl_se->dl_deadline * rem_runtime)) {
> > + rel_deadline = dl_se->dl_deadline;
> > + rem_runtime = dl_se->dl_runtime;
> > + }
>
> So, are you basically checking if current remaining bw can be consumed
> safely?
I check if the current runtime (rescaled based on the capacity) is
smaller than the time to the current scheduling deadline (basically, if
it can be consumed in time).
However, if
q / (d - t) > Q / P
(where "q" is the current runtime, "d" is the scheduling deadline, "Q"
is the maximum runtime, and "P" is the CBS period), then a new
scheduling deadline will be generated (later), and the runtime will be
reset to Q... So, I need to use the maximum budget and CBS period for
checking if the task fits in the core.
>
> I'm not actually sure if looking at dynamic values is what we need to
> do at this stage. By considering static values we fix admission
> control (and scheduling). Aren't dynamic values more to do with
> energy tradeoffs (and so to be introduced when starting to look at
> the energy model)?
Using the current runtime and scheduling deadline might allow to
migrate a task to SMALL cores (if its remaining runtime is small
enough), even if the rescaled Q is larger than P.
So, in theory it might allow to reduce the load on big cores.
If we decide that this is overkilling, I can just drop the patch.
Luca
> Another pair of hands maybe is to look at the dynamic spare bw of CPUs
> (to check that we don't overload CPUs).
>
> Thanks,
>
> - Juri
next prev parent reply other threads:[~2019-05-08 9:24 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-06 4:48 [RFC PATCH 0/6] Capacity awareness for SCHED_DEADLINE Luca Abeni
2019-05-06 4:48 ` [RFC PATCH 1/6] sched/dl: Improve deadline admission control for asymmetric CPU capacities Luca Abeni
2019-05-07 13:48 ` Quentin Perret
2019-05-07 13:55 ` Vincent Guittot
2019-05-07 14:02 ` Quentin Perret
2019-05-07 14:25 ` luca abeni
2019-05-07 14:31 ` Quentin Perret
2019-05-07 14:43 ` luca abeni
2019-07-08 11:22 ` Dietmar Eggemann
2019-07-08 15:05 ` Quentin Perret
2019-06-18 16:41 ` Alessio Balsini
2019-05-06 4:48 ` [RFC PATCH 2/6] sched/dl: Capacity-aware migrations Luca Abeni
2019-05-07 13:35 ` Quentin Perret
2019-05-07 14:17 ` luca abeni
2019-05-07 15:04 ` Quentin Perret
2019-05-07 14:10 ` Quentin Perret
2019-05-07 14:41 ` luca abeni
2019-05-07 15:02 ` Quentin Perret
2019-05-08 8:04 ` Juri Lelli
2019-05-08 8:17 ` luca abeni
2019-07-04 12:05 ` Dietmar Eggemann
2019-07-08 7:41 ` luca abeni
2019-07-08 10:41 ` Dietmar Eggemann
2019-05-06 4:48 ` [RFC PATCH 3/6] sched/dl: Try better placement even for deadline tasks that do not block Luca Abeni
2019-05-07 14:13 ` Quentin Perret
2019-05-07 16:00 ` Morten Rasmussen
2019-05-08 8:01 ` Juri Lelli
2019-05-08 8:14 ` luca abeni
2019-05-08 9:22 ` Juri Lelli
2019-07-08 13:55 ` Peter Zijlstra
2019-07-09 13:24 ` luca abeni
2019-07-09 13:42 ` Peter Zijlstra
2019-07-11 11:17 ` Dietmar Eggemann
2019-07-11 12:00 ` Peter Zijlstra
2019-07-11 15:33 ` Dietmar Eggemann
2019-07-09 14:44 ` Dietmar Eggemann
2019-05-06 4:48 ` [RFC PATCH 4/6] sched/dl: Improve capacity-aware wakeup Luca Abeni
2019-05-08 9:08 ` Juri Lelli
2019-05-08 9:24 ` luca abeni [this message]
2019-05-08 12:05 ` Juri Lelli
2019-05-08 12:47 ` luca abeni
2019-05-08 13:10 ` Juri Lelli
2019-05-08 14:12 ` luca abeni
2019-05-06 4:48 ` [RFC PATCH 5/6] sched/dl: If the task does not fit anywhere, select the fastest core Luca Abeni
2019-05-06 4:48 ` [RFC PATCH 6/6] sched/dl: Try not to select a too fast core Luca Abeni
2019-05-07 15:57 ` Quentin Perret
2019-05-08 6:26 ` luca abeni
2019-05-09 13:46 ` Quentin Perret
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190508112437.74661fa8@nowhere \
--to=luca.abeni@santannapisa.it \
--cc=bristot@redhat.com \
--cc=gregkh@linuxfoundation.org \
--cc=joel@joelfernandes.org \
--cc=juri.lelli@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=luc.vanoostenryck@gmail.com \
--cc=mingo@redhat.com \
--cc=morten.rasmussen@arm.com \
--cc=patrick.bellasi@arm.com \
--cc=paulmck@linux.ibm.com \
--cc=peterz@infradead.org \
--cc=quentin.perret@arm.com \
--cc=rafael@kernel.org \
--cc=tommaso.cucinotta@santannapisa.it \
--cc=vincent.guittot@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).