From: Patrick Bellasi <patrick.bellasi@arm.com>
To: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>, Tejun Heo <tj@kernel.org>,
"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
Viresh Kumar <viresh.kumar@linaro.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Paul Turner <pjt@google.com>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Juri Lelli <juri.lelli@redhat.com>, Todd Kjos <tkjos@google.com>,
Joel Fernandes <joelaf@google.com>,
Steve Muckle <smuckle@google.com>,
Suren Baghdasaryan <surenb@google.com>
Subject: Re: [PATCH v3 09/14] sched/core: uclamp: propagate parent clamps
Date: Fri, 17 Aug 2018 15:45:40 +0100 [thread overview]
Message-ID: <20180817144540.GL2960@e110439-lin> (raw)
In-Reply-To: <804c7937-2c47-0781-9c53-a8ef8eb04530@arm.com>
On 17-Aug 15:43, Dietmar Eggemann wrote:
> On 08/06/2018 06:39 PM, Patrick Bellasi wrote:
> >In order to properly support hierarchical resources control, the cgroup
> >delegation model requires that attribute writes from a child group never
> >fail but still are (potentially) constrained based on parent's assigned
> >resources. This requires to properly propagate and aggregate parent
> >attributes down to its descendants.
>
> I don't understand the reason mentioned here:
>
> IMHO, a write to a child's (tg1/tg11) cpu.rt_runtime_us can fail if the
> value is restricted by the parents value:
Well... that's my interpretation after this discussion:
https://lore.kernel.org/lkml/20180410200514.GA793541@devbig577.frc2.facebook.com/
AFAIU, what has not to fail is a write to a parent, which wants to enforce
more restrictive constraints to child groups. Thus, if we have for example:
tg1: util_max=100%
tg1/tg11: util_max=80%
It should be possible without errors to set:
tg1: util_max=50%
and then enforce a 50% util_max to tg1/tg11 tasks too and eventually
use "effective" attributes to expose the effective value used at each
level of the hierarchy.
> root@juno:/sys/fs/cgroup/cpu# cat cpu.rt_*
> 1000000
> 950000
> root@juno:/sys/fs/cgroup/cpu# cat tg1/cpu.rt_*
> 1000000
> 0
> root@juno:/sys/fs/cgroup/cpu# cat tg1/tg11/cpu.rt_*
> 1000000
> 0
> root@juno:/sys/fs/cgroup/cpu# echo 950000 > tg1/tg11/cpu.rt_runtime_us
> -bash: echo: write error: Invalid argument
> root@juno:/sys/fs/cgroup/cpu# echo 950000 > tg1/cpu.rt_runtime_us
> root@juno:/sys/fs/cgroup/cpu# echo 950000 > tg1/tg11/cpu.rt_runtime_us
> root@juno:/sys/fs/cgroup/cpu#
This example is using the legacy hierarcy (cgroups v1).
AFAIK the default hierarcy (cgroups v2) has a much more stricy set of
requirements for the "delegation model".
> >Let's implement this mechanism by adding a new "effective" clamp value
> >for each task group. The effective clamp value is defined as the smaller
> >value between the clamp value of a group and the effective clamp value
> >of its parent. This represent also the clamp value which is actually
> >used to clamp tasks in each task group.
> >
> >Since it can be interesting for tasks in a cgroup to know exactly what
> >is the currently propagated/enforced configuration, the effective clamp
> >values are exposed to user-space by means of a new pair of read-only
> >attributes: cpu.util.{min,max}.effective.
>
> I assume here that the cpu.util.{min,max} of the child will not be used any
> more because the 'effective' counterparts are taken instead.
Yes, the "effective" attributes are the one used in kernel space for
the actual clamping.
However, the cpu.util.{min,max} of a child are still required as soon
as the parent relax its constraints... when we use their value to
set the "effective" value.
> I wonder if this propagation not been provided with only cpu.util.{min,max}?
In the example before, if we use the same variables we miss the
opportunity to reset:
tg1/tg11: util_max=80%
as soon as tg1's util_max goes back to 100%.
--
#include <best/regards.h>
Patrick Bellasi
next prev parent reply other threads:[~2018-08-17 14:45 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-06 16:39 [PATCH v3 00/14] Add utilization clamping support Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 01/14] sched/core: uclamp: extend sched_setattr to support utilization clamping Patrick Bellasi
2018-08-06 16:50 ` Randy Dunlap
2018-08-09 8:39 ` Patrick Bellasi
2018-08-09 15:20 ` Randy Dunlap
2018-08-07 9:59 ` Juri Lelli
2018-08-13 12:14 ` Patrick Bellasi
2018-08-13 12:27 ` Juri Lelli
2018-08-07 12:35 ` Juri Lelli
2018-08-09 9:14 ` Patrick Bellasi
2018-08-09 9:50 ` Juri Lelli
2018-08-09 15:23 ` Patrick Bellasi
2018-08-10 7:50 ` Juri Lelli
2018-08-17 10:34 ` Quentin Perret
2018-08-17 10:57 ` Patrick Bellasi
2018-08-17 11:14 ` Quentin Perret
2018-08-06 16:39 ` [PATCH v3 02/14] sched/core: uclamp: map TASK's clamp values into CPU's clamp groups Patrick Bellasi
2018-08-14 11:25 ` Pavan Kondeti
2018-08-14 15:21 ` Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 03/14] sched/core: uclamp: add CPU's clamp groups accounting Patrick Bellasi
2018-08-14 15:44 ` Dietmar Eggemann
2018-08-14 16:49 ` Patrick Bellasi
2018-08-15 9:37 ` Dietmar Eggemann
2018-08-15 10:54 ` Patrick Bellasi
2018-08-15 10:59 ` Dietmar Eggemann
2018-08-16 13:32 ` Patrick Bellasi
2018-08-16 13:37 ` Quentin Perret
2018-08-16 13:45 ` Dietmar Eggemann
2018-08-16 14:21 ` Quentin Perret
2018-08-16 15:00 ` Dietmar Eggemann
2018-08-17 11:04 ` Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 04/14] sched/core: uclamp: update CPU's refcount on clamp changes Patrick Bellasi
2018-08-15 15:02 ` Dietmar Eggemann
2018-08-16 13:22 ` Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 05/14] sched/cpufreq: uclamp: add utilization clamping for FAIR tasks Patrick Bellasi
2018-08-08 13:18 ` Vincent Guittot
2018-08-09 15:30 ` Patrick Bellasi
2018-08-15 15:30 ` Dietmar Eggemann
2018-08-16 13:53 ` Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 06/14] sched/cpufreq: uclamp: add utilization clamping for RT tasks Patrick Bellasi
2018-08-07 13:26 ` Juri Lelli
2018-08-09 15:34 ` Patrick Bellasi
2018-08-09 16:03 ` Vincent Guittot
2018-08-13 10:12 ` Patrick Bellasi
2018-08-13 10:50 ` Juri Lelli
2018-08-13 12:07 ` Vincent Guittot
2018-08-13 12:09 ` Vincent Guittot
2018-08-13 12:49 ` Patrick Bellasi
2018-08-13 14:06 ` Vincent Guittot
2018-08-13 15:01 ` Patrick Bellasi
2018-08-16 10:34 ` Dietmar Eggemann
2018-08-16 13:40 ` Patrick Bellasi
2018-08-07 13:54 ` Quentin Perret
2018-08-09 15:41 ` Patrick Bellasi
2018-08-09 15:55 ` Quentin Perret
2018-08-13 10:17 ` Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 07/14] sched/core: uclamp: enforce last task UCLAMP_MAX Patrick Bellasi
2018-08-16 15:43 ` Dietmar Eggemann
2018-08-16 16:47 ` Patrick Bellasi
2018-08-16 17:10 ` Dietmar Eggemann
2018-08-16 17:27 ` Patrick Bellasi
2018-08-16 17:20 ` Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 08/14] sched/core: uclamp: extend cpu's cgroup controller Patrick Bellasi
2018-08-17 12:21 ` Dietmar Eggemann
2018-08-17 14:24 ` Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 09/14] sched/core: uclamp: propagate parent clamps Patrick Bellasi
2018-08-16 9:09 ` Pavan Kondeti
2018-08-16 14:07 ` Patrick Bellasi
2018-08-17 13:43 ` Dietmar Eggemann
2018-08-17 14:45 ` Patrick Bellasi [this message]
2018-08-17 15:50 ` Dietmar Eggemann
2018-08-20 10:01 ` Dietmar Eggemann
2018-08-20 12:28 ` Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 10/14] sched/core: uclamp: map TG's clamp values into CPU's clamp groups Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 11/14] sched/core: uclamp: use TG's clamps to restrict Task's clamps Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 12/14] sched/core: uclamp: add system default clamps Patrick Bellasi
2018-08-16 9:13 ` Pavan Kondeti
2018-08-16 14:37 ` Patrick Bellasi
2018-08-20 10:18 ` Dietmar Eggemann
2018-08-20 12:27 ` Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 13/14] sched/core: uclamp: update CPU's refcount on TG's clamp changes Patrick Bellasi
2018-08-06 16:39 ` [PATCH v3 14/14] sched/core: uclamp: use percentage clamp values Patrick Bellasi
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=20180817144540.GL2960@e110439-lin \
--to=patrick.bellasi@arm.com \
--cc=dietmar.eggemann@arm.com \
--cc=joelaf@google.com \
--cc=juri.lelli@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pm@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=morten.rasmussen@arm.com \
--cc=peterz@infradead.org \
--cc=pjt@google.com \
--cc=rafael.j.wysocki@intel.com \
--cc=smuckle@google.com \
--cc=surenb@google.com \
--cc=tj@kernel.org \
--cc=tkjos@google.com \
--cc=vincent.guittot@linaro.org \
--cc=viresh.kumar@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).