From: catalin.marinas@arm•com (Catalin Marinas)
To: linux-arm-kernel@lists•infradead.org
Subject: [RFC][PATCH 1/2] ARM64: add cpu topology definition
Date: Wed, 14 Aug 2013 12:27:20 +0100 [thread overview]
Message-ID: <20130814112720.GB43445@MacBook-Pro.local> (raw)
In-Reply-To: <20130729095400.GB32383@mudshark.cambridge.arm.com>
On Mon, Jul 29, 2013 at 10:54:01AM +0100, Will Deacon wrote:
> On Mon, Jul 29, 2013 at 10:46:06AM +0100, Vincent Guittot wrote:
> > On 27 July 2013 12:42, Hanjun Guo <hanjun.guo@linaro•org> wrote:
> > > Power aware scheduling needs the cpu topology information to improve the
> > > cpu scheduler decision making.
> >
> > It's not only power aware scheduling. The scheduler already uses
> > topology and cache sharing when CONFIG_SCHED_MC and/or
> > CONFIG_SCHED_SMT are enable. So you should also add these configs for
> > arm64 so the scheduler can use it
>
> ... except that the architecture doesn't define what the AFF fields in MPIDR
> really represent. Using them to make key scheduling decisions relating to
> cache proximity seems pretty risky to me, especially given the track record
> we've seen already on AArch32 silicon. It's a convenient register if it
> contains the data we want it to contain, but we need to force ourselves to
> come to terms with reality here and simply use it as an identifier for a
> CPU.
>
> Can't we just use the device-tree to represent this topological data for
> arm64? Lorenzo has been working on bindings in this area.
Catching up on email after holiday - I agree with Will here, we should
use DT for representing the topology (or ACPI) and not rely on the MPIDR
value.
--
Catalin
next prev parent reply other threads:[~2013-08-14 11:27 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-27 10:42 [RFC][PATCH 1/2] ARM64: add cpu topology definition Hanjun Guo
2013-07-27 10:42 ` [RFC][PATCH 2/2] ARM64: introduce cluster id and make a difference between socket id Hanjun Guo
2013-07-29 9:38 ` Vincent Guittot
2013-07-30 7:46 ` Hanjun Guo
2013-07-29 9:46 ` [RFC][PATCH 1/2] ARM64: add cpu topology definition Vincent Guittot
2013-07-29 9:54 ` Will Deacon
2013-07-29 10:39 ` Vincent Guittot
2013-07-29 13:36 ` Dave Martin
2013-07-29 17:23 ` Lorenzo Pieralisi
2013-07-30 8:09 ` Hanjun Guo
2013-08-14 11:27 ` Catalin Marinas [this message]
2013-08-15 1:00 ` Hanjun Guo
2013-07-29 10:15 ` Sudeep KarkadaNagesha
2013-07-29 10:28 ` Vincent Guittot
2013-07-30 7:49 ` Hanjun Guo
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