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[31.30.174.132]) by smtp.gmail.com with ESMTPSA id m7sm6527201ejo.95.2021.06.28.01.34.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Jun 2021 01:34:23 -0700 (PDT) Date: Mon, 28 Jun 2021 10:34:20 +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: <20210628083420.v47xbbtcgjj2mu47@gator> References: <20210625052338.4875-1-gshan@redhat.com> <20210625070217.4ffmfe7nwlusbbjc@gator> <20210625070656.j373hveemf5cdch4@gator> <41643136-798b-a0f3-aee7-b6af94a2fc67@redhat.com> <20210625101821.3t3vgj2pnw3hqpzm@gator> <62d04903-e4f3-2302-d530-5942e33ae116@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <62d04903-e4f3-2302-d530-5942e33ae116@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 25, 2021 at 09:14:49PM +1000, Gavin Shan wrote: > On 6/25/21 8:18 PM, Andrew Jones wrote: > > 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. > > > > [...] > > > 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. > > > > [...] > > > > > 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>; > > > + }; > > > + > > [...] > > Thanks, Drew. As 'base-address' is dummy address and invalid. So we > would note it as suggestion. With your suggestion integrated, how about > something like this? > > ============================================================================== > 4 - Empty memory nodes > ============================================================================== > > 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. The 'base-address' could be the summation of highest > memory address plus the NUMA node ID. However, the NUMA node IDs and > distance maps are still valid and memory may be added into them through > hotplug afterwards. > > : > > 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 */ > memory@0x100000002 { > device_type = "memory"; > reg = <0x1 0x2 0x0 0x0>; > numa-node-id = <2>; > }; > > /* Empty memory node */ > memory@0x100000003 { > device_type = "memory"; > reg = <0x1 0x3 0x0 0x0>; > numa-node-id = <3>; > }; > > : > > Thanks, > Gavin > > Looks good to me. Thanks, drew