Re: [RFC PATCH 1/9] sched,cgroup: Add interface for latency-nice

From: Joel Fernandes <joel@joelfernandes.org>
To: Parth Shah <parth@linux.ibm.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Qais Yousef <qais.yousef@arm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Patrick Bellasi <patrick.bellasi@arm.com>,
	Subhra Mazumdar <subhra.mazumdar@oracle.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	Thomas Glexiner <tglx@linutronix.de>,
	steven.sistare@oracle.com, Dhaval Giani <dhaval.giani@oracle.com>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	Mel Gorman <mgorman@techsingularity.net>
Subject: Re: [RFC PATCH 1/9] sched,cgroup: Add interface for latency-nice
Date: Mon, 20 Apr 2020 15:14:31 -0400	[thread overview]
Message-ID: <20200420191431.GB67569@google.com> (raw)
In-Reply-To: <7d4637c8-da8c-463d-30c6-a55c0a173316@linux.ibm.com>

On Mon, Apr 20, 2020 at 04:56:55PM +0530, Parth Shah wrote:

> >>
> >> There are two presentations/discussions planned:
> >>
> >> "Introducing Latency Nice for Scheduler Hints and Optimizing Scheduler
> >> Task Wakeup" and "The latency nice use case for Energy-Aware-Scheduling
> >> (EAS) in Android Common Kernel (ACK)"
> >>
> >> We'll probably merge those two into one presentation/discussion.
> >>
> >> So far we have Parth's per-task implementation
> >>
> >> https://lore.kernel.org/lkml/20200228090755.22829-1-parth@linux.ibm.com
> > 
> > Cool, I see it has some Reviewed-by tags so that's a good sign. Will
> > look more into that.
> > 
> >> What's missing is the per-taskgroup implementation, at least from the
> >> standpoint of ACK.
> >>
> >> The (mainline) EAS use-case for latency nice is already in ACK
> >> (android-5.4):
> >>
> >> https://android.googlesource.com/kernel/common/+/760b82c9b88d2c8125abfc5f732cc3cd460b2a54
> > 
> > Yes, I was aware of this. But if we use task groups, then the
> > transition from schedtune -> uclamp means now the tasks that use
> > uclamp would also be subjected to cpu.shares. That's why we were
> > looking into the per-task interface and glad there's some work on this
> > already done.
> > 
> 
> Yes, that series of latency_nice seems to be in good shape to be used for
> any usecases. Hopefully, OSPM will lead to its upstreaming sooner :-)

Cool :)

> But at the end, we aim to have both the per-task and cgroup based interface
> to mark the latency_nice value of a task.

Ok. We'd likely use the per-task interface unless we decide to assign
cpu.shares for the groups as well.

> Till, then I'm finding some generic use-cases to show benefits of such task
> attribute to increase community interest.

Ok. Feel free to add ChromeOS as a usecase as well.

thanks,

 - Joel