Messages in this thread | | | Date | Fri, 20 May 2022 15:56:39 +0100 | From | Sudeep Holla <> | Subject | Re: [PATCH v2 8/8] arch_topology: Add support to build llc_sibling on DT platforms |
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On Fri, May 20, 2022 at 02:33:46PM +0200, Dietmar Eggemann wrote: > On 18/05/2022 11:33, Sudeep Holla wrote: > > ACPI PPTT provides cache identifiers and especially the last level cache > > identifier is used in obtaining last level cache siblings amongst CPUs. > > > > While we have the cpu map representing all the CPUs sharing last level > > cache in the cacheinfo driver, it is populated quite late in the boot > > while the information is needed to build scheduler domains quite early. > > > > On DT platforms we can use the pointer to the last level cache as the > > firmware identifier for the last level cache and build the cpumap sharing > > the last level cache based on the same. > > [...] > > > diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h > > index 58cbe18d825c..d8a36b0e27c9 100644 > > --- a/include/linux/arch_topology.h > > +++ b/include/linux/arch_topology.h > > @@ -69,6 +69,7 @@ struct cpu_topology { > > int cluster_id; > > int package_id; > > int llc_id; > > + void *llc_fw_node; > > Would be nicer if you could set llc_id directly to avoid all this > addition sync `llc_id and llc_fw_node` code. ACPI PPTT has this > ACPI_PTR_DIFF() macro which IMHO lets it create distinct ids. >
Indeed, I initially thought so, but they are 64 bit pointers and choosing one reference is difficult to take some sort of diff while in ACPI it is in a static table and we could use the reference to the top of the table.
-- Regards, Sudeep
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