linux-kernel - Re: [PATCH v5 7/9] arm64: Topology, rename cluster

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Date:   Mon, 18 Dec 2017 12:42:29 +0000
From:   Morten Rasmussen <morten.rasmussen@...s.arm.com>
To:     Jeremy Linton <jeremy.linton@....com>
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        linux-acpi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        sudeep.holla@....com, hanjun.guo@...aro.org, rjw@...ysocki.net,
        will.deacon@....com, catalin.marinas@....com,
        gregkh@...uxfoundation.org, viresh.kumar@...aro.org,
        mark.rutland@....com, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, jhugo@...eaurora.org,
        wangxiongfeng2@...wei.com, Jonathan.Zhang@...ium.com,
        ahs3@...hat.com, Jayachandran.Nair@...ium.com,
        austinwc@...eaurora.org, lenb@...nel.org, morten.rasmussen@....com,
        dietmar.eggemann@....com
Subject: Re: [PATCH v5 7/9] arm64: Topology, rename cluster_id

On Fri, Dec 15, 2017 at 10:36:35AM -0600, Jeremy Linton wrote:
> Hi,
> 
> On 12/13/2017 12:02 PM, Lorenzo Pieralisi wrote:
> >[+Morten, Dietmar]
> >
> >$SUBJECT should be:
> >
> >arm64: topology: rename cluster_id
> 
> Sure..
> 
> >
> >On Fri, Dec 01, 2017 at 04:23:28PM -0600, Jeremy Linton wrote:
> >>Lets match the name of the arm64 topology field
> >>to the kernel macro that uses it.
> >>
> >>Signed-off-by: Jeremy Linton <jeremy.linton@....com>
> >>---
> >>  arch/arm64/include/asm/topology.h |  4 ++--
> >>  arch/arm64/kernel/topology.c      | 27 ++++++++++++++-------------
> >>  2 files changed, 16 insertions(+), 15 deletions(-)
> >>
> >>diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h
> >>index c4f2d50491eb..118136268f66 100644
> >>--- a/arch/arm64/include/asm/topology.h
> >>+++ b/arch/arm64/include/asm/topology.h
> >>@@ -7,14 +7,14 @@
> >>  struct cpu_topology {
> >>  	int thread_id;
> >>  	int core_id;
> >>-	int cluster_id;
> >>+	int physical_id;
> >
> >package_id ?
> 
> Given the macro is topology_physical_package_id, either makes sense to me.
> <shrug> I will change it in the next set.

I would vote for package_id too. arch/arm has 'socket_id' though.

> >
> >It has been debated before, I know. Should we keep the cluster_id too
> >(even if it would be 1:1 mapped to package_id - for now) ?
> 
> Well given that this patch replaces the patch that did that at your
> request..
> 
> I was hoping someone else would comment here, but my take at this point is
> that it doesn't really matter in a functional sense at the moment.
> Like the chiplet discussion it can be the subject of a future patch along
> with the patches which tweak the scheduler to understand the split.
> 
> BTW, given that i'm OoO next week, and the following that are the holidays,
> I don't intend to repost this for a couple weeks. I don't think there are
> any issues with this set.
> 
> >
> >There is also arch/arm to take into account, again, this patch is
> >just renaming (as it should have named since the beginning) a
> >topology level but we should consider everything from a legacy
> >perspective.

arch/arm has gone for thread/core/socket for the three topology levels
it supports.

I'm not sure what short term value keeping cluster_id has? Isn't it just
about where we make the package = cluster assignment? Currently it is in
the definition of topology_physical_package_id. If we keep cluster_id
and add package_id, it gets moved into the MPIDR/DT parsing code. 

Keeping cluster_id and introducing a topology_cluster_id function could
help cleaning up some of the users of topology_physical_package_id that
currently assumes package_id == cluster_id though.

Morten