From: Peter Zijlstra <peterz@infradead.org>
To: Vikram Mulukutla <markivx@codeaurora.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@kernel.org>,
Srivatsa Vaddagiri <vatsa@codeaurora.org>,
Steve Muckle <steve.muckle@linaro.org>,
Olav Haugan <ohaugan@codeaurora.org>,
Syed Rameez Mustafa <rameezmustafa@codeaurora.org>,
Joonwoo Park <joonwoop@codeaurora.org>,
Pavankumar Kondeti <pkondeti@codeaurora.org>,
Saravana Kannan <skannan@codeaurora.org>,
Bryan Huntsman <bryanh@codeaurora.org>,
Juri Lelli <juri.lelli@arm.com>,
Morten Rasmussen <morten.rasmussen@arm.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Chris Redpath <chris.redpath@arm.com>,
Robin Randhawa <robin.randhawa@arm.com>,
Patrick Bellasi <patrick.bellasi@arm.com>,
Todd Kjos <tkjos@google.com>,
Srinath Sridharan <srinathsr@google.com>,
Andres Oportus <andresoportus@google.com>,
Leo Yan <leo.yan@linaro.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Vikram Mulukutla <markivx@codeauorora.org>
Subject: Re: [RFC PATCH 0/3] sched: Introduce Window Assisted Load Tracking
Date: Fri, 28 Oct 2016 11:23:08 +0200 [thread overview]
Message-ID: <20161028092308.GZ3102@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <107c17a07b42bb5aa9039600db4a47a5@codeaurora.org>
On Fri, Oct 28, 2016 at 12:55:52AM -0700, Vikram Mulukutla wrote:
> On 2016-10-28 00:29, Peter Zijlstra wrote:
> >On Fri, Oct 28, 2016 at 12:10:39AM -0700, Vikram Mulukutla wrote:
> >>
> >>We propose Window-Assisted Load Tracking (WALT) as an alternative or
> >>additional load tracking scheme in lieu of or along with PELT, one
> >>that in our estimation better tracks task demand and CPU utilization
> >>especially for use cases on mobile devices. WALT was conceived by
> >>Srivatsa Vaddagiri to provide better perf-per-watt numbers on
> >>asymmetric CPU (frequency and/or IPC) implementations, (specifically
> >>on Qualcomm Snapgdragon chipsets running Android) and its metrics
> >>have been used to guide task placement and p-state selection (load
> >>balancing in CFS still uses PELT statistics). WALT is now present in
> >>the android-common kernel as well.
> >
> >And how come we only learn of it after its already shipping? Isn't that
> >arse backwards?
>
> Yes, but also we were not confident that it would be close to being
> acceptable
> upstream since it was intricately tied to our HMP scheduler. However now
> that
> more parties including the folks at ARM are interested, and given that EAS
> exists and schedutil was merged into mainline, we felt it the right time
> to try and introduce the concept. In general we are seriously trying to get
> more things upstream and converge.
That's good to hear, great!
That said, I would much prefer to modify/augment existing PELT stuff
than to add an entirely new set of accounting on the side of it. But
yes, I (and others) are aware of the pain points you mentioned with
using the PELT signal for schedutil.
We'll have to see what we can come up with.
next prev parent reply other threads:[~2016-10-28 9:23 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-28 7:10 [RFC PATCH 0/3] sched: Introduce Window Assisted Load Tracking Vikram Mulukutla
2016-10-28 7:10 ` [RFC PATCH 1/3] sched: Introduce structures necessary for WALT Vikram Mulukutla
2016-10-28 7:10 ` [RFC PATCH 2/3] sched: Introduce Window-Assisted CPU utilization Tracking Vikram Mulukutla
2016-10-28 7:38 ` Peter Zijlstra
2016-10-28 7:43 ` Peter Zijlstra
2016-10-28 7:58 ` Vikram Mulukutla
2016-10-28 7:46 ` Peter Zijlstra
2016-10-28 8:03 ` Vikram Mulukutla
2016-10-28 7:52 ` Peter Zijlstra
2016-10-28 7:10 ` [RFC PATCH 3/3] sched: Introduce WALT hooks into core and scheduling classes Vikram Mulukutla
2016-10-28 7:57 ` Peter Zijlstra
2016-10-28 7:29 ` [RFC PATCH 0/3] sched: Introduce Window Assisted Load Tracking Peter Zijlstra
2016-10-28 7:55 ` Vikram Mulukutla
2016-10-28 9:23 ` Peter Zijlstra [this message]
2016-10-28 7:49 ` Peter Zijlstra
2016-10-28 7:57 ` Vikram Mulukutla
2016-10-28 8:49 ` Peter Zijlstra
2016-10-31 15:07 ` Vikram Mulukutla
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