Re: [PATCH v2] base/node / acpi: Change 'node_hmem_attrs' to 'access_coordinates'

[Dave Jiang]

On 6/13/23 00:57, Greg KH wrote:
> On Mon, Jun 12, 2023 at 03:32:42PM -0700, Dave Jiang wrote:
> > Dan Williams suggested changing the struct 'node_hmem_attrs' to
> > 'access_coordinates' [1]. The struct is a container of r/w-latency and
> > r/w-bandwidth numbers. Moving forward, this container will also be used by
> > CXL to store the performance characteristics of each link hop in
> > the PCIE/CXL topology. So, where node_hmem_attrs is just the access
> > parameters of a memory-node, access_coordinates applies more broadly
> > to hardware topology characteristics. The observation is that seemed like
> > an excercise in having the application identify "where" it falls on a
> > spectrum of bandwidth and latency needs. For the tuple of read/write-latency
> > and read/write-bandwidth, "coordinates" is not a perfect fit. Sometimes it
> > is just conveying values in isolation and not a "location" relative to
> > other performance points, but in the end this data is used to identify the
> > performance operation point of a given memory-node. [2]
> >
> > Link: http://lore.kernel.org/r/64471313421f7_1b66294d5@xxxxxxxxxxxxxxxxxxxxxxxxx.notmuch/
> > Link: https://lore.kernel.org/linux-cxl/645e6215ee0de_1e6f2945e@xxxxxxxxxxxxxxxxxxxxxxxxx.notmuch/
> > Suggested-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> > Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> > Signed-off-by: Dave Jiang <dave.jiang@xxxxxxxxx>
> >
> > ---
> >
> > Hi Greg and Rafael,
> > please consider ACK this patch and Dan can take it through the
> > CXL upstream tree. The remaining ACPI [1] and CXL [2] patches for enabling
> > CXL QoS class data have dependency on this patch. Thank you!
> >
> > [1]: https://lore.kernel.org/linux-cxl/168333141100.2290593.16294670316057617744.stgit@djiang5-mobl3/T/#t
> > [2]: https://lore.kernel.org/linux-cxl/168451588868.3470703.3527256859632103687.stgit@djiang5-mobl3/T/#t
> Isn't this going to conflict with the version that I have in the
> driver-core-next tree as commit 7810f4dc8795 ("base/node: Use 'property'
> to identify an access parameter")?
>
> Or was that a different thing?

Yes this is a different thing and should not conflict. But a small 
dependency on the mentioned commit above however:

@@ -168,7 +168,7 @@ static ssize_t property##_show(struct device *dev,			\
 			   char *buf)					\
 {									\
 	return sysfs_emit(buf, "%u\n",					\
-			  to_access_nodes(dev)->hmem_attrs.property);	\
+			  to_access_nodes(dev)->coord.property);	\
 }									\
 static DEVICE_ATTR_RO(property)
 


> thanks,
>
> greg k-h