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From: Peter Zijlstra <peterz@infradead.org>
To: Ley Foon Tan <lftan.linux@gmail.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>,
	Ingo Molnar <mingo@redhat.com>,
	Quentin Perret <quentin.perret@arm.com>,
	Greg KH <gregkh@linuxfoundation.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	linux-kernel@vger.kernel.org
Subject: Re: sched: Question about big and little cores system with SMP and EAS
Date: Wed, 16 Jun 2021 13:39:05 +0200	[thread overview]
Message-ID: <YMni2eclmqf05cL4@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CAFiDJ5-ZO=BuSwBPPPecZhLyjyipTLenQxgCK=t52Pj7r659sQ@mail.gmail.com>

On Wed, Jun 16, 2021 at 07:29:26PM +0800, Ley Foon Tan wrote:
> Hi all
> 
> Would like to ask the experts here regarding the Symmetric
> Multi-Processing mode (SMP) with Energy aware scheduler (EAS) support
> on the big + little cores system.

And the you ask a question unrelated to either Symmetric MP or EAS :-)

> Hardware system:
> Big and little cores have almost the same ISA, but the big core has
> some extension instructions that little core doesn't have.

That problem is unrelated to big.Little / EAS, also by definition that
is not SMP seeing how the 'S' is a blatant lie.

The simplest solution is to simply disallow usage of the extended ISA
and force mandate the common subset. The complicated answer is something
along the lines of:

  https://lkml.kernel.org/r/20210608180313.11502-1-will@kernel.org

  reply	other threads:[~2021-06-16 11:39 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-16 11:29 sched: Question about big and little cores system with SMP and EAS Ley Foon Tan
2021-06-16 11:39 ` Peter Zijlstra [this message]
2021-06-16 13:20   ` Dietmar Eggemann
2021-06-17  5:00     ` Ley Foon Tan
2021-06-17  7:51       ` Morten Rasmussen

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