From: Qais Yousef <qais.yousef@arm.com>
To: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Jonathan Corbet <corbet@lwn.net>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Luis Chamberlain <mcgrof@kernel.org>,
Kees Cook <keescook@chromium.org>,
Iurii Zaikin <yzaikin@google.com>,
Quentin Perret <qperret@google.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Patrick Bellasi <patrick.bellasi@matbug.net>,
Pavan Kondeti <pkondeti@codeaurora.org>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 1/2] sched/uclamp: Add a new sysctl to control RT default boost value
Date: Tue, 21 Apr 2020 12:27:34 +0100 [thread overview]
Message-ID: <20200421112733.4jbguidgbqwzhv23@e107158-lin.cambridge.arm.com> (raw)
In-Reply-To: <de020088-3b06-3674-dab9-244ae577cc54@arm.com>
On 04/21/20 13:18, Dietmar Eggemann wrote:
> On 20/04/2020 17:13, Qais Yousef wrote:
> > On 04/20/20 10:29, Dietmar Eggemann wrote:
> >> On 03.04.20 14:30, Qais Yousef wrote:
> >>
> >> [...]
> >>
> >>> @@ -924,6 +945,14 @@ uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id)
> >>> return uc_req;
> >>> }
> >>>
> >>> +static void uclamp_rt_sync_default_util_min(struct task_struct *p)
> >>> +{
> >>> + struct uclamp_se *uc_se = &p->uclamp_req[UCLAMP_MIN];
> >>> +
> >>> + if (!uc_se->user_defined)
> >>> + uclamp_se_set(uc_se, sysctl_sched_rt_default_uclamp_util_min, false);
> >>> +}
> >>> +
> >>> unsigned long uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id)
> >>> {
> >>> struct uclamp_se uc_eff;
> >>> @@ -1030,6 +1059,12 @@ static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p)
> >>> if (unlikely(!p->sched_class->uclamp_enabled))
> >>> return;
> >>>
> >>> + /*
> >>> + * When sysctl_sched_rt_default_uclamp_util_min value is changed by the
> >>> + * user, we apply any new value on the next wakeup, which is here.
> >>> + */
> >>> + uclamp_rt_sync_default_util_min(p);
> >>> +
> >>
> >> Does this have to be an extra function? Can we not reuse
> >> uclamp_tg_restrict() by slightly rename it to uclamp_restrict()?
> >
> > Hmm the thing is that we're not restricting here. In contrary we're boosting,
> > so the name would be misleading.
>
> I always thought that we're restricting p->uclamp_req[UCLAMP_MIN].value (default 1024) to
> sysctl_sched_rt_default_uclamp_util_min (0-1024)?
The way I look at it is that we're *setting* it to
sysctl_sched_rt_default_uclamp_util_min if !user_defined.
The restriction mechanism that ensures this set value doesn't escape
cgroup/global restrictions setup.
>
> root@h960:~# echo 999 > /proc/sys/kernel/sched_rt_default_util_clamp_min
>
> [ 118.028582] uclamp_eff_get() [rtkit-daemon 410] tag=0 uclamp_id=0 uc_req.value=1024
> [ 118.036290] uclamp_eff_get() [rtkit-daemon 410] tag=1 uclamp_id=0 uc_req.value=1024
> [ 125.181747] uclamp_eff_get() [rtkit-daemon 410] tag=0 uclamp_id=0 uc_req.value=1024
> [ 125.189443] uclamp_eff_get() [rtkit-daemon 410] tag=1 uclamp_id=0 uc_req.value=1024
> [ 131.213211] uclamp_restrict() [rtkit-daemon 410] p->uclamp_req[0].value=999
> [ 131.220201] uclamp_eff_get() [rtkit-daemon 410] tag=0 uclamp_id=0 uc_req.value=999
> [ 131.227792] uclamp_eff_get() [rtkit-daemon 410] tag=1 uclamp_id=0 uc_req.value=999
> [ 137.181544] uclamp_eff_get() [rtkit-daemon 410] tag=0 uclamp_id=0 uc_req.value=999
> [ 137.189170] uclamp_eff_get() [rtkit-daemon 410] tag=1 uclamp_id=0 uc_req.value=999
>
> >> This function will then deal with enforcing restrictions, whether system
> >> and taskgroup hierarchy related or default value (latter only for rt-min
> >> right now since the others are fixed) related.
> >>
> >> uclamp_eff_get() -> uclamp_restrict() is called from:
> >>
> >> 'enqueue_task(), uclamp_update_active() -> uclamp_rq_inc() -> uclamp_rq_inc_id()' and
> >>
> >> 'task_fits_capacity() -> clamp_task_util(), rt_task_fits_capacity() -> uclamp_eff_value()' and
> >>
> >> 'schedutil_cpu_util(), find_energy_efficient_cpu() -> uclamp_rq_util_with() -> uclamp_eff_value()'
> >>
> >> so there would be more check-points than the one in 'enqueue_task() -> uclamp_rq_inc()' now.
> >
> > I think you're revolving around the same idea that Patrick was suggesting.
> > I think it is possible to do something in uclamp_eff_get() too.
>
> Yeah, I read https://lore.kernel.org/linux-doc/20200415074600.GA26984@darkstar again.
>
> Everything which moves enforcing sysctl_sched_rt_default_uclamp_util_min closer to 'uclamp_eff_get() ->
> uclamp_(tg_)restrict()' is fine with me.
Cool.
Thanks
--
Qais Yousef
next prev parent reply other threads:[~2020-04-21 11:27 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-03 12:30 [PATCH 1/2] sched/uclamp: Add a new sysctl to control RT default boost value Qais Yousef
2020-04-03 12:30 ` [PATCH 2/2] Documentation/sysctl: Document uclamp sysctl knobs Qais Yousef
2020-04-14 18:21 ` [PATCH 1/2] sched/uclamp: Add a new sysctl to control RT default boost value Patrick Bellasi
2020-04-15 7:46 ` Patrick Bellasi
2020-04-20 15:04 ` Qais Yousef
2020-04-20 8:24 ` Dietmar Eggemann
2020-04-20 15:19 ` Qais Yousef
2020-04-21 0:52 ` Steven Rostedt
2020-04-21 11:16 ` Dietmar Eggemann
2020-04-21 11:23 ` Qais Yousef
2020-04-20 14:50 ` Qais Yousef
2020-04-15 10:11 ` Quentin Perret
2020-04-20 15:08 ` Qais Yousef
2020-04-20 8:29 ` Dietmar Eggemann
2020-04-20 15:13 ` Qais Yousef
2020-04-21 11:18 ` Dietmar Eggemann
2020-04-21 11:27 ` Qais Yousef [this message]
2020-04-22 10:59 ` Dietmar Eggemann
2020-04-22 13:13 ` Qais Yousef
2020-05-11 15:40 Qais Yousef
2020-05-11 17:18 ` Qais Yousef
2020-05-12 2:10 ` Pavan Kondeti
2020-05-12 11:46 ` Qais Yousef
2020-05-15 11:08 ` Patrick Bellasi
2020-05-18 8:31 ` Dietmar Eggemann
2020-05-18 16:49 ` Qais Yousef
2020-05-28 13:23 ` Peter Zijlstra
2020-05-28 15:58 ` Qais Yousef
2020-05-28 16:11 ` Peter Zijlstra
2020-05-28 16:51 ` Qais Yousef
2020-05-28 18:29 ` Peter Zijlstra
2020-05-28 19:08 ` Patrick Bellasi
2020-05-28 19:20 ` Dietmar Eggemann
2020-05-29 9:11 ` Qais Yousef
2020-05-29 10:21 ` Mel Gorman
2020-05-29 15:11 ` Qais Yousef
2020-05-29 16:02 ` Mel Gorman
2020-05-29 16:05 ` Qais Yousef
2020-05-29 10:08 ` Mel Gorman
2020-05-29 16:04 ` Qais Yousef
2020-05-29 16:57 ` Mel Gorman
2020-06-02 16:46 ` Dietmar Eggemann
2020-06-03 8:29 ` Patrick Bellasi
2020-06-03 10:10 ` Mel Gorman
2020-06-03 14:59 ` Vincent Guittot
2020-06-03 16:52 ` Qais Yousef
2020-06-04 12:14 ` Vincent Guittot
2020-06-05 10:45 ` Qais Yousef
2020-06-09 15:29 ` Vincent Guittot
2020-06-08 12:31 ` Qais Yousef
2020-06-08 13:06 ` Valentin Schneider
2020-06-08 14:44 ` Steven Rostedt
2020-06-11 10:13 ` Qais Yousef
2020-06-09 17:10 ` Vincent Guittot
2020-06-11 10:24 ` Qais Yousef
2020-06-11 12:01 ` Vincent Guittot
2020-06-23 15:44 ` Qais Yousef
2020-06-24 8:45 ` Vincent Guittot
2020-06-05 7:55 ` Patrick Bellasi
2020-06-05 11:32 ` Qais Yousef
2020-06-05 13:27 ` Patrick Bellasi
2020-06-03 9:40 ` Mel Gorman
2020-06-03 12:41 ` Qais Yousef
2020-06-04 13:40 ` Mel Gorman
2020-06-05 10:58 ` Qais Yousef
2020-06-11 10:58 ` Qais Yousef
2020-06-16 11:08 ` Qais Yousef
2020-06-16 13:56 ` Lukasz Luba
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