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[31.30.174.132]) by smtp.gmail.com with ESMTPSA id s18sm2526921ejh.12.2021.06.25.03.18.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 25 Jun 2021 03:18:22 -0700 (PDT) Date: Fri, 25 Jun 2021 12:18:21 +0200 From: Andrew Jones To: Gavin Shan Cc: devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, rdunlap@infradead.org, robh+dt@kernel.org, shan.gavin@gmail.com Subject: Re: [PATCH v4] Documentation, dt, numa: Add note to empty NUMA node Message-ID: <20210625101821.3t3vgj2pnw3hqpzm@gator> References: <20210625052338.4875-1-gshan@redhat.com> <20210625070217.4ffmfe7nwlusbbjc@gator> <20210625070656.j373hveemf5cdch4@gator> <41643136-798b-a0f3-aee7-b6af94a2fc67@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <41643136-798b-a0f3-aee7-b6af94a2fc67@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 25, 2021 at 06:36:48PM +1000, Gavin Shan wrote: > On 6/25/21 5:06 PM, Andrew Jones wrote: > > 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 > > > > --- > > > > 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. > > > > > Drew, thanks for your comments. Yeah, it sounds sensible to create > a new section for it and an example would be more helpful. Please > check if below changes are fine to you. I probably need Randy's review > again. > > I'm trying to avoid too many revisions for this sort of trivial patch, > even though I already had. However, it's time frame for v5.14 and I'm > pushing this to be merged during the cycle. We must revise until we're satisfied... Also, I wouldn't call writing specifications trivial. > > --- a/Documentation/devicetree/bindings/numa.txt > +++ b/Documentation/devicetree/bindings/numa.txt > @@ -103,7 +103,65 @@ Example: > }; > ============================================================================== > -4 - Example dts > +4 - Empty memory node nodes > +============================================================================== > + > +Empty memory nodes, which no memory resides in, are allowed. The 'length' > +field of 'reg' property is zero, but 'base-address' is dummy and invalid is a dummy address and is invalid. > +for these empty memory nodes. Can drop this "for these empty memory nodes" that's clear from the context. > However, the NUMA node IDs and distance maps > +for them are still valid, but memory may be added into them through hotplug ^ drop 'for them' ^ Again, this should be "and". "but" is a contrastive conjunction. We want to express that the nodes are valid *and* may have memory hotplugged later. > +afterwards. I'll just rewrite it: Empty memory nodes, which no memory resides in, are allowed. The 'length' field of the 'reg' property is zero, but the 'base-address' is a dummy address and invalid. However, the NUMA node IDs and distance maps are still valid and memory may be added into them through hotplug afterwards. > + > +Example: > + > + memory@0 { > + device_type = "memory"; > + reg = <0x0 0x0 0x0 0x80000000>; > + numa-node-id = <0>; > + }; > + > + memory@0x80000000 { > + device_type = "memory"; > + reg = <0x0 0x80000000 0x0 0x80000000>; > + numa-node-id = <1>; > + }; > + > + /* Empty memory node */ You should write how you've selected the dummy addresses for the empty memory nodes, perhaps here in the /* Empty memory node */ comments or above in the paragraph or both. > + memory@0x100000000 { > + device_type = "memory"; > + reg = <0x1 0x0 0x0 0x0>; > + numa-node-id = <2>; > + }; > + > + /* Empty memory node */ > + memory@0x180000000 { > + device_type = "memory"; > + reg = <0x1 0x80000000 0x0 0x0>; > + numa-node-id = <3>; > + }; > + > + distance-map { > + compatible = "numa-distance-map-v1"; > + distance-matrix = <0 0 10>, > + <0 1 20>, > + <0 2 40>, > + <0 3 20>, > + <1 0 20>, > + <1 1 10>, > + <1 2 20>, > + <1 3 40>, > + <2 0 40>, > + <2 1 20>, > + <2 2 10>, > + <2 3 20>, > + <3 0 20>, > + <3 1 40>, > + <3 2 20>, > + <3 3 10>; > + }; > + > +============================================================================== > +5 - Example dts > ============================================================================== > Dual socket system consists of 2 boards connected through ccn bus and > > > Thanks, > Gavin > > Thanks, drew