linux-kernel - Re: [PATCH v4] Documentation, dt, numa: Add note to empty NUMA node

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Message-ID: <20210625070656.j373hveemf5cdch4@gator>
Date:   Fri, 25 Jun 2021 09:06:56 +0200
From:   Andrew Jones <drjones@...hat.com>
To:     Gavin Shan <gshan@...hat.com>
Cc:     devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        rdunlap@...radead.org, robh+dt@...nel.org, shan.gavin@...il.com
Subject: Re: [PATCH v4] Documentation, dt, numa: Add note to empty NUMA node

On Fri, Jun 25, 2021 at 09:02:17AM +0200, Andrew Jones wrote:
> On Fri, Jun 25, 2021 at 01:23:38PM +0800, Gavin Shan wrote:
> > The empty memory nodes, where no memory resides in, are allowed.
> > For these empty memory nodes, the 'len' of 'reg' property is zero.
> > The NUMA node IDs are still valid and parsed, but memory can be
> > added to them through hotplug afterwards. I finds difficulty to
> > get where it's properly documented.
> > 
> > So lets add note to empty memory nodes in the NUMA binding doc.
> > 
> > Signed-off-by: Gavin Shan <gshan@...hat.com>
> > ---
> >  Documentation/devicetree/bindings/numa.txt | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/numa.txt b/Documentation/devicetree/bindings/numa.txt
> > index 21b35053ca5a..0fc882e44270 100644
> > --- a/Documentation/devicetree/bindings/numa.txt
> > +++ b/Documentation/devicetree/bindings/numa.txt
> > @@ -109,6 +109,10 @@ Example:
> >  Dual socket system consists of 2 boards connected through ccn bus and
> >  each board having one socket/soc of 8 cpus, memory and pci bus.
> >  
> > +Note that empty memory nodes, which no memory resides in, are allowed.
> > +The NUMA node IDs in these empty memory nodes are still valid, but
> > +memory can be added into them through hotplug afterwards.
> 
> Please change the second sentence to:
> 
>   The NUMA node IDs in these empty memory nodes are still valid and
>   memory may be added into them through hotplug afterwards.
> 
> But, this doesn't look like the right place for this paragraph. You're
> adding the paragraph to the example section, but the example doesn't have
> any empty memory nodes.
> 
> I think the paragraph should be added to section "2 - numa-node-id" and an

Or maybe even create a new section for it.

> example empty memory node should be provided. Also, the commit message
> talks about the length of 'reg' being zero, which is an important
> distinction which should also be documented.
> 
> Thanks,
> drew
> 
> > +
> >  	memory@...000 {
> >  		device_type = "memory";
> >  		reg = <0x0 0xc00000 0x0 0x80000000>;
> > -- 
> > 2.23.0
> >